Novel and Emerging Markers of Chronic or Low-Grade Inflammation

Abstract

Standard biomarkers of acute inflammation C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) may be subject to limitations in the assessment of inflammation that is more chronic or low-grade in nature. There is a need for accurate markers of low-grade or chronic inflammation that are stable and not subject to acute factors. Novel or emerging inflammatory biomarkers that may represent promising alternatives include the neutrophil-lymphocyte ratio, glycoprotein acetyls, and soluble urokinase plasminogen activator receptor. These markers have demonstrated utility in a variety of clinical conditions (including cancer and cardiovascular disease), may offer increased sensitivity in people with some conditions, and may outperform the standard ESR and CRP in specific situations. These markers can also be positively influences by healthy lifestyle changes and habits. While the complete clinical relevance and best uses of these markers is still being elucidated, they may offer new avenues for exploring the multi-faceted nature of chronic inflammation.

Introduction

Low-grade systemic inflammation is increasingly recognized for its important role in a variety of disease states. Not only is chronic low-grade inflammation (LGI) implicated in the aging process, but LGI is also seen in association with numerous health conditions, including cardiovascular diseases (CVDs, including stroke, myocardial infarction, and peripheral artery disease), post-traumatic stress disorder (where it is thought to be a potential driver of the increased chronic disease risk seen in affected individuals), obesity, musculoskeletal pain conditions, autism spectrum disorder, and diabetes.^1

–6 LGI can also be seen in association with bipolar disorder and schizophrenia.⁷ Moreover, it is related to lifestyle factors such as smoking and stress.⁸ LGI or more overt inflammation are also certainly seen in autoimmune conditions.^8,9 LGI is also inversely correlated with lower gut microbial diversity, and challenges to gut barrier integrity are thought to contribute to LGI.^6,10

Inflammation contributes to disease through a number of important mechanisms. These mechanisms bear exploring in further detail as they can subsequently inform the way such inflammation is detected or assessed clinically. Inflammation is a normal response to tissue injury or infection, which prompts the initiation of a cascade of chemical signals designed to heal the affected area. At its most basic level, the migration of blood cells into tissues, followed by the activation of these cells and their interplay with local cells at the tissue site, are classic components of the inflammatory response.

Chemical signals at the site of damage promote chemotaxis of leukocytes to the area of damage or infection. Recruited leukocytes in turn produce cytokines that enhance the response (including interleukins [ILs] such as IL-1β, IL-6, tumor necrosis factors including tumor necrosis factor-alpha [TNF-α], and chemokines). Cytokines are primarily released from monocytes, macrophages, dendritic cells, and lymphocytes. While these cytokines have local effects at the tissue site, many enter the systemic circulation where they also exert more widespread effects. This includes stimulating increased production and secretion of several “acute phase reactant” compounds, such as C-reactive protein (CRP), fibrinogen, and haptoglobin, from the liver.

These proteins, along with inflammation-mediating enzymes, such as superoxide dismutase, glutathione peroxidase, and cyclooxygenase-2, all perform important roles in tissue repair and the inflammatory response. Additionally, local microcirculatory changes, such as alterations in vascular permeability, allow for additional leukocyte recruitment and aggregation as well as the release of inflammatory mediators. The release of inflammatory mediators recruits additional inflammatory cells (such as macrophages or tissue-resident adipocytes) to or at the site of injury.^11,12

The appropriate resolution of an inflammatory response requires degradation of inflammatory mediators and chemokines (leading to reduced recruitment of circulating leukocytes to the site of injury) along with an increased production of pro-resolving lipid mediators and cytokines (including transforming growth factor beta). If this process if not appropriately regulated, if the source of tissue damage is not resolved, or if there is a continuing stimulus, chronic inflammation can be the result. Ongoing inflammation can lead to continued leukocyte recruitment, remodeling of the extracellular matrix, angiogenesis, and either cellular proliferation or death.^11,12

The traditional markers of systemic inflammation are erythrocyte sedimentation rate (ESR) and CRP. ESR assesses the rate at which red blood cells fall in the plasma of an anticoagulated blood sample over a particular period of time. The first to note an association between illness and a change in the sedimentation of blood was Dr. John Hunter in the late 1700s. Dr. Edmund Biernacki then developed clinical use of ESR in the late 1800s, publishing two articles (in Polish and German) and presenting to the Warsaw Medical Society on his use of this marker.^13,14 Further developments in the use of ESR as a diagnostic tool were later made by Dr. Robert Fahraeus in 1918 and by Dr. Alf Westergren in the 1920s, who utilized ESR as a diagnostic test and marker of disease prognosis (for tuberculosis).

The standards Westergren created for ESR measurement remain widely used to this day. In fact, the Westergren method of ESR measurement was confirmed as the gold standard by the International Committee for Standardization in Haematology in 1973, and again by both the International Committee for Standardization in Haematology and the Clinical and Laboratory Standards Institute in 2011. Thus, the Westergren method for ESR determination has now been in use for close to a century. Often assessed over a 60-minute period (units as millimeters per hour), newer methodology can provide results over shorter periods of time, that is, 5 minutes.^13
–15

CRP is a member of the pentraxin protein family, a group of pattern recognition proteins that participates in innate immunity. CRP also functions as a nonspecific acute phase reactant. The initial discovery of CRP came in the 1930s, when Tillet and Francis studied the blood of their patients with acute streptococcal pneumonia. They made the observation that this protein from the sera of pneumonia patients interacted with the C-polysaccharide of the Streptococcus pneumoniae cell wall (hence the name eventually give to this substance, CRP). CRP was originally measured qualitatively, but more precise methodology (including high-sensitivity CRP [hsCRP] assays) now allows for the quantitative assessment of even low levels of CRP.¹⁵

The dynamics of these two markers of inflammation are seen in Table 1.^14

–17 CRP rises quickly in response to acute inflammation, while ESR takes longer to increase. With its short half-life of four to seven hours, CRP also declines quickly once inflammation has resolved. ESR, on the other hand, may take weeks to resolve once inflammation has subsided.

Table 1.

Dynamics of Erythrocyte Sedimentation Rate and C-Reactive Protein

Erythrocyte sedimentation rate	C-reactive protein
Indirect measure of level of inflammation	Direct measure of inflammatory response
Begins increasing within 24–48 hours of onset of inflammation	Can increase by 50–100 mg/L within 4–6 hours of mild to moderate inflammatory stimulus; CRP levels double every 8 hours and peak 36–50 hours after onset of inflammation
Isolated finding of modestly increased ESR in asymptomatic person not a cause for extensive non-directed workup	Mild increases in CRP (2–10 mg/L) considered consistent with metabolic inflammation or periodontal disease; moderate increases (10–100) can occur with trauma or flares of chronic inflammatory disease
Markedly elevated ESR (>100 mm/hour) usually has an obvious etiology, such as infection, cancer, or temporal arteritis	Markedly elevated CRP (>100–500 mg/L) strongly associated with bacterial infection
Decreases slowly as inflammation resolves; can take weeks to fully normalize	Short half-life (4–7 hours); therefore decreases rapidly once inflammation resolves
Can be impacted by factors other than inflammation: size, shape, and number of red blood cells; levels of fibrinogen and immunoglobulins; renal function; age; sex; pregnancy; medications	Synthesized in the liver, so liver failure can impair production

CRP, C-reactive protein; ESR, erythrocyte sedimentation rate.

While both ESR and CRP are typically increased in acute inflammatory conditions, the utility of these markers for more chronic or LGI may vary. The utility of ESR, for example, has decreased over time as other methods have been developed, and while it remains helpful in the diagnosis or monitoring of temporal arteritis, polymyalgia rheumatica, and some cases of rheumatoid arthritis, the use of ESR as a general screening tool is not recommended due to low sensitivity and specificity.^14,17 In fact, both ESR and CRP can lack specificity and sensitivity. Therefore, these assays must be used in conjunction with clinical presentation and the physical exam for either diagnosis or monitoring purposes, and these tests are probably most appropriate when there is either a high or low index of suspicion for disease.¹⁵

A CRP level between 3 and 10 mg/L is thought to be consistent with LGI,¹⁸ although a normal CRP may not necessarily rule out the presence of low-grade inflammatory states. Additionally, while a modestly elevated (>3 mg/L) CRP is the current standard for determining chronic inflammation, this carries limitations due to the nature of CRP itself. Active infections may obscure results.¹⁹ Additionally, with its short half-life and ability to rise and fall rapidly, CRP is inherently transitory and exhibits substantial biologic variability. For example, in one study of healthy blood donors with six samples provided over a 22-day span, the variation of CRP was 50%. This is consistent with other studies which indicate biologic variation ranging from 30% up to 63%.²⁰ The ideal characteristics for a marker of chronic inflammation are necessarily different from those for a suitable marker of acute inflammation. As Rasmussen, Petersen, and Eugen-Olsen point out, a good marker of LGI or chronic inflammatory processes needs to be temporally and biologically stable, accurate, reliable, and minimally influenced by acute or short-term factors.¹⁹

Beyond ESR and CRP, a number of other biomarkers of inflammation are currently being explored. There are potential advantages in expanding the range of possible biomarkers for inflammation. In some situations, the advantage of other markers may be related to cost or convenience, as they are readily obtainable using inexpensive or frequently acquired standard assays (as in the case of the neutrophil-lymphocyte ratio, or NLR, readily obtainable using a standard complete blood count [CBC]). Additionally, other biomarkers may offer increased sensitivity in some conditions, or may outperform the standard ESR and CRP in particular situations. This article explores some of these expanded markers of inflammation, beyond ESR and CRP.

Neutrophil-Lymphocyte Ratio

The absolute NLR is an inexpensive and easily acquired measure that can be obtained utilizing a standard CBC. NLR is firstly an important marker of immune homeostasis, reflecting the balance between innate immunity (via neutrophils) and adaptive immunity (via lymphocytes). Not only are neutrophils responsible for the first line of defense against pathogens, but they are also the main effector cells participating in the inflammatory response. Neutrophils secrete numerous inflammatory cytokines and chemokines that also attract and enhance the function of other immune cells. These include dendritic cells, B cells, natural killer cells, and mesenchymal stem cells. During a systemic inflammatory response, neutrophil apoptosis is suppressed, and the pool of neutrophils increases (to support innate neutrophil-mediated killing). Thus, neutrophils rise in proportion to lymphocytes, increasing the NLR.²¹ NLR is therefore considered to be a valuable marker of the systemic inflammatory response (and a better reflection of inflammation than the total white blood cell [WBC] count or the individual WBC components alone).²²

A normal NLR is considered to be 1 to 2, with a ratio exceeding 3.0 or falling under 0.7 in adults considered abnormal (although, as will be seen below, a wide range of cut-offs has been used in the literature to define an elevated NLR). An NLR of 2.3 to 3.0 may indicate early pathology or inflammation (ranges proposed by Zahorec, with more on this below).²³ NLR has been shown to be a reliable prognosticator in a number of disease states or conditions that involve significant chronic inflammation. These include cancer, cardiovascular and respiratory diseases, and coronavirus disease 2019 (COVID-19).

Inflammation is likely to be a strong contributor to cancer development and progression, and NLR is thought to reflect the balance between activation of the inflammatory response, and antitumor immune activity.²⁴ NLR has been shown to have multiple uses in oncology. These include correlation with tumor size, staging, and disease stratification. NLR is also associated with lymphatic invasiveness or metastatic potential.²³ A higher NLR has been shown to be associated with an increase in the infiltration of macrophages in the peritumoral space, and higher levels of IL-17.²⁵ Additionally, NLR is an independent prognosticator of overall survival (OS), disease-free survival (DFS), and cancer-specific survival, and has a demonstrated utility in monitoring the response to therapy, whether chemotherapy, radiation, or immune checkpoint blockade is the mode of treatment.²³

Regarding specific tumor types, NLR has been broadly applied as a marker in studies in people with a wide variety of diagnoses. A sample of these studies is summarized in Table 2.

Table 2.

Studies Demonstrating Utility of Neutrophil-Lymphocyte Ratio in People with Solid Tumors

Diagnosis/patient population	Utility of NLR	Reference(s)
Pts with progressive urothelial carcinoma receiving checkpoint inhibitors	Independent prognostic factor, with NLR >5 associated with poorer OS (P < 0.001)	Bamias et al.²⁶
Pts with SCLC or NSCLC receiving tyrosine kinase inhibitor	Higher post-tx NLR associated with poorer PFS in people with SCLC, and with poorer OS and PFS in people with NSCLC	Chen et al.^27,28
Men with metastatic prostate cancer on androgen deprivation therapy	Higher baseline NLR predicts poorer OS, with NLR as a continuous covariate, per 1 unit increase, having an hazard ratio of 1.05 (95% CI 1.02–1.08; P = 0.0003)	de Wit et al.²⁹
Women with early stage triple negative breast cancer	Women with low NLR (<3 vs. ≥3) have higher PCR (P < 0.001) rates, and better OS and DFS with PCR attainment (P < 0.001 and P = 0.006, respectively)	Asano et al.³⁰
Pts with human epidermal growth factor receptor 2+ advanced gastric cancer receiving first line trastuzumab	High NLR correlates with significantly worse median OS and PFS (P = 0.002 and P = 0.005, respectively)	Park et al.³¹
Metastatic pancreatic adenocarcinoma	High NLR at time of dx is a marker of poor prognosis; NLR >5 is an independent prognosis marker for both OS and PFS (P = 0.001 and P = 0.0026, respectively)	McLellan et al.³²
Pts with metastatic colon cancer receiving first line treatment	Higher baseline NLR (≥3 vs. <3) associated with significantly shorter PFS and OS (P = 0.017 and P < 0.001, respectively)	Dell'Aquilla et al.³³
Early-stage colorectal cancer	High NLR (≥2.43 vs. <2.43) associated with worse OS compared to lower NLR (P = 0.058); both high NLR and the combination of NLR and carcinoembryonic antigen are significantly associated with reduced DFS (P = 0.047 and P < 0.001, respectively)	Zhan et al.³⁴

DFS, disease-free survival; dx, diagnosis; NLR, neutrophil-lymphocyte ratio; NSCLC, non-small cell lung cancer; OS, overall survival; PCR, pathological complete response; PFS, progression-free survival; pts, patients; SCLC, small cell lung cancer; tx, treatment.

In a 2014 systematic review and meta-analysis, high NLR was associated with adverse outcomes across a broad range of solid tumor types. A total of 100 studies with 40,559 participants were included. An NLR >4 carried a hazard ratio (HR) for OS of 1.81 (95% CI = 1.67–1.97; P < 0.001), and was also associated with HRs of 1.61 for cancer-specific survival, 1.63 for progression free survival (PFS), and 2.27 for DFS (P < 0.001 for all). The relationship between high NLR and poorer OS held for all tumor types and stages. NLR's prognostic effect was greatest in people with mesothelioma (HR = 2.35; 95% CI = 1.89–2.92), followed by pancreatic cancer, renal cell carcinoma, colorectal cancer, gastroesophageal cancer, non-small cell lung cancer, cholangiocarcinoma and hepatocellular carcinoma (HCC) (HRs ranging from 2.35; 95% CI = 1.89–2.92 for people with mesothelioma, to HR = 1.43; 95% CI = 1.23–1.66 for those with HCC).²⁵ Other meta-analyses have used a cut-off value of 3.0 for the prognostic value of NLR in people with solid tumors.²³

NLR as a marker of systemic inflammation is also associated with poorer prognosis in people with CVD. Among patients admitted with acute heart failure (HF), NLR independently and significantly predicted 30-day all-cause mortality, 60-day rehospitalization or cardiovascular (CV)-related mortality, and 180-day all-cause mortality and CV-related mortality (adjusted HR per log₂ NLR increment of 1.66 [1.22–2.25], P = 0.001; 1.33 [1.12–1.57], P = 0.001; 1.27 [1.08–1.50], P = 0.003; and 1.24 [1.04–1.49], P = 0.018).³⁵

In another study of over 5800 patients undergoing aortic valve replacement for aortic stenosis, a high baseline NLR (defined as ≥4.20) was associated with increased risk of rehospitalization or death at three years, compared to low baseline NLR (NLR ≤2.70) (58.4% vs. 41.0%; adjusted HR of 1.39; 95% CI 1.18–1.63; P < 0.0001). Additionally, a 1-unit decrease in NLR between baseline and one year follow up was associated with a lower risk of rehospitalization or death (HR 0.86, 95% CI 0.82–0.89; P < 0.0001).²² NLR also predicts all-cause mortality (with a cut-off of ≥2.1) in people with cardiomyopathy who have received implantable cardioverter-defibrillators, mortality in those with acute myocardial infarct (NLR ≥8.16), and functional outcomes in people with acute ischemic stroke (at a cut-off of ≥2.71).^36
–38

NLR is also a prognostic marker among people with acute respiratory distress syndrome (ARDS) or COVID infection, disease states in which inflammation has been shown to play a very important role. In a 2019 study in people with ARDS whose NLR was stratified into quartiles, this biomarker was shown to be predictive of mortality. Median NLR by quartile was 6.88 (4.61–7.94), 13.06 (11.35–14.89), 20.99 (19.09–23.19), and 39.39 (32.63–50.15), and 28-day mortality for each group was 10.7%, 19.6%, 41.4%, and 53.6% (P < 0.001), respectively.³⁹

A 2020 study conducted in people with moderate to severe COVID (enrolled between April and July 2020, with partial pressure of oxygen in arterial blood/fraction of inspired oxygen [PaO₂/FiO₂] ratio between 200 and 300, or respiratory rate >24 per minute, and decreased oxygen saturation on room air [SpO₂ < 93%]) found that NLR >10 was significantly associated with death (HR 9.97, 95% CI 3.65–27.13, P < 0.001).⁴⁰

Another early pandemic study (this time conducted between January and March 2020 in Sichuan province, China) determined that in a group of people presenting with severe COVID infection, those with high NLR (>9.8) had a higher incidence of ARDS as well as use of both noninvasive and invasive mechanical ventilation (P = 0.005, P = 0.002, and P = 0.048, respectively). An NLR cutoff value of 11 was determined for those with moderate-severe ARDS (defined as oxygen index <150), with the authors suggesting these findings may have implications for clinical management, since early prediction of more severe ARDS can help clinicians best allocate healthcare or intensive care resources during times or in areas where such resources are scarce.⁴¹ An additional study conducted during the early pandemic (March–June 2020) found that even a more modest definition of elevated NLR (≥3) was independently associated with 30-day mortality in people being admitted for COVID infection (odds ratio [OR] 2.2, 95% CI 1.5–4.5, P < 0.05).⁴²

In a cross-sectional study of African patients (N = 240) conducted later in the pandemic (patients being admitted for COVID between August and October 2021), an NLR of 9.47 was determined to be the optimal cut-off for prediction of mortality, with a sensitivity and specificity of 88.7% and 95.4%, respectively (area under the curve [AUC]: 0.95, 95% CI 0.92–98; P < 0.001). In addition to this, an NLR of 5.86 was found to be an effective cut-off value for the prediction of disease severity, with a sensitivity and specificity of 92.2% and 75%, respectively (AUC: 0.85, 95% CI 0.800–0.905; P < 0.001).⁴³

Note the large variety of cut-off values for either “normal” or “elevated” NLR seen in the studies above. Clearly, the optimal NLR value for different clinical scenarios remains to be determined. In a study specifically conducted in healthy adults from South Korea, yielding 12,160 samples from more than 10,000 patients (with a mean age of 47 in male participants and 46 in female participants), the mean NLR was 1.65.⁴⁴ Using data from the National Health and Nutrition Examination Survey (NHANES) as a reflection of the United States general population (mean age of 52.0), the mean NLR was 2.3. Keep in mind that the NHANES population included large numbers of people with health conditions: 48% were past or current smokers, 70% were either overweight or obese, 10% had diabetes, and 35% had hypertension (HTN).⁴⁵ There is certainly further work to be done in determining optimal NLR range in health and disease.

NLR can also be confounded by a number of factors. NLR has been found to positively correlate with age in healthy subjects.⁴⁶ NLR may also rise acutely in response to exercise.⁴⁷ Acute increases in NLR provoked by exercise can reach levels up to sixfold above baseline, with absolute NLR values over 10 possible with prolonged higher-intensity exercise.^47,48 NLR generally returns to baseline six to nine hours post cessation of exercise, although with prolonged or very strenuous exercise, it may take more than 24 hours to reach baseline status.⁴⁹ This may need to be taken into account in people undergoing athletic training. Multiple lifestyle and demographic characteristics are also independently associated with NLR, including gender, race, marital status, physical activity level, history of smoking, alcohol intake, and body mass index (BMI). Appropriate adjustment of these factors needs to be performed to ensure accuracy of NLR as a prognosticator.⁵⁰ The association of NLR with modifiable risk factors (alcohol or tobacco use, physical activity, and BMI) suggests that lifestyle change may offer an opportunity to reduce this biomarker of inflammation.

As mentioned above, Zahorec has suggested a normal range for NLR of 1 to 2, with values falling <0.7 or >3.0 considered abnormal, and an NLR of 2 to 3 considered a “gray zone” consistent with subclinical inflammation or LGI. These numbers were proposed based on the analysis of data from about 200 studies that examined the use of NLR for screening, prognostication, or stratification in differing disease states (Table 3).²³

Table 3.

Neutrophil-Lymphocyte Ratio Interpretation

NLR value	Interpretation	Conditions
1–2	Normal	Healthy state
2–3	“Gray zone”; subclinical inflammation or low-grade inflammation	Diabetes, metabolic syndrome, psychiatric conditions, autoimmunity, cardiovascular disease, mild to moderate COVID. Values in this range prognostic for both localized and advanced stage cancer.
3–7	Mild to moderate inflammation
7–11	Moderate to severe inflammation	Moderate to severe ARDS, severe COVID, infections, sepsis
11–17	Severe inflammation	Severe sepsis, bacteremia
17–23	Critical levels of inflammation	Septic shock or trauma
≥23		Multiple trauma, terminal cancer

Adapted from Zahorec²³ and Kourilovitch and Galarza-Maldonado.⁵¹

ARDS, acute respiratory distress syndrome.

Glycoprotein Acetyls

As mentioned above, the inflammatory response leads to the generation of acute phase reactants. Structurally, these compounds are almost all N-linked glycoproteins. The overall rise in acute phase reactants during inflammation therefore coincides with an increase in the number of circulating N-glycan oligosaccharide branches. Glycoprotein acetyls (GlycA) can be used to measure the number of these N-glycan branches attached to circulating acute phase reactant proteins. Because most circulating N-glycosylated proteins are acute phase reactants, the test is reflective of overall levels of these inflammatory compounds.

While GlycA levels have been demonstrated to positively correlate with CRP (as well as IL-6 and fibrinogen), GlycA may offer some distinct advantages over CRP as an inflammatory marker. CRP measures one discrete protein, while GlycA as a composite measures both the number and complexity of N-glycan branches from a pool of circulating proteins. GlycA levels are less variable between men and women compared to CRP. GlycA is also more stable, with less day-to-day and intra-individual variability compared to CRP.⁵²

In an analysis by Otvos et al., intraindividual variability for GlycA, assessed weekly for five weeks in healthy people, was 4.3%. This was lower than for each of the other biomarkers tested, including hsCRP (29.2%), total cholesterol (5.7%), and triglycerides (18.0%).⁵³ Ballout and Remaley have suggested that the relationship of GlycA to CRP can be thought of as analogous to that of hemoglobin A1c (HbA1c) to blood sugar, with GlycA showing lower biologic variability and improved stability over time.⁵² While two serial measures of hsCRP are the guideline standard for inflammation in the assessment of CVD risk, a single measure of GlycA is considered sufficient.⁵³ In addition to this, GlycA has been shown to correlate with a higher number of metabolomics markers than hsCRP (such as low-density lipoprotein, intermediate-density lipoprotein, and very large and large high-density lipoprotein particles and their constituents), even after adjusting for confounders, and GlycA inversely correlates with gut microbial diversity, while hsCRP does not.⁵⁴

GlycA Quartiles in Muhlestein 2018

Quartile 1: ≤ 281 μmol/L

Quartile 2: 282–339 μmol/L

Quartile 3: 340–407 μmol/L

Quartile 4: ≥ 408 μmol/L

GlycA Quartiles in Akinkuolie 2014

Quartile 1: ≤ 326 μmol/L

Quartile 2: 327–369 μmol/L

Quartile 3: 370–416 μmol/L

Quartile 4: ≥ 417 μmol/L

GlycA Quartiles in Jang 2020, expressed as median (interquartile interval)

Quartile 1: 314 (294–327) μmol/L

Quartile 2: 358 (348–367) μmol/L

Quartile 3: 396 (386–406) μmol/L

Quartile 4: 451 (434–477) μmol/L

GlycA is a strong predictor of CVD and is probably best represented in the literature by its association with CVD risk and cardiometabolic conditions. In Akinkuolie et al.'s study, GlycA was predictive of the 15-year risk of CVD incidence and mortality in women. Baseline GlycA was quantified in 24,491 women who were healthy at baseline. Using a Cox regression model (including age, ethnicity, smoking status, blood pressure, medications, menopausal status, BMI, and diabetes), the HRs for CVD across quartiles of GlycA were 1.00, 1.10 (95% CI 0.92–1.30), 1.34 (95% CI 1.13–1.58), and 1.64 (95% CI 1.39–1.93), similar to results seen for hsCRP.⁵⁵ In a 2022 analysis (by Jang et al.) from the Dallas Heart Study and Multi-Ethnic Study of Atherosclerosis (MESA), while both GlycA and hsCRP were associated with incident CVD, hsCRP was more strongly predictive of stroke, while GlycA more strongly predicted incident myocardial infarction (MI) among 9785 participants without baseline CVD (median follow-up of 13.4 years; HR for quartile 4 vs. quartile 1 of 1.90, 95% CI 1.39–2.58).⁵⁶

In an additional study of MESA participants aged 45 to 84 without baseline CVD or HF, people who fell into the highest quartile for GlycA experienced increased risk of developing HF (HR 1.48 [95% CI 1.01–2.18]) compared to those in the lowest quartile.⁵⁷ Among those with existing CVD, GlycA is also predictive of future outcomes. In the Intermountain Heart Collaborative Study (Muhlestein et al.), people who underwent coronary angiography (N = 2996) were followed for 7.0 ± 2.8 years. People in the highest quartile for baseline GlycA had a higher risk of future major adverse cardiovascular events (HR: 1.43; 95% CI: 1.22–1.69; P < 0.0001).⁵⁸

Aside from CVD, GlycA has also been shown to be associated with other chronic inflammatory conditions, including autoimmune conditions, HTN, obesity, and metabolic disease, as well as with the risk of future severe infections.^59,60 In Joshi et al.'s study comparing people with psoriasis to healthy controls from two cohorts (total N of 273 with psoriasis and 139 controls), GlycA was higher in people with psoriasis compared to controls, and increased in a dose-dependent fashion with psoriasis severity (P < 0.0001 for both cohorts). Additionally, in people with psoriasis, vascular inflammation (assessed by Positron Emission Tomography/Computed Tomography) and coronary artery disease (CAD) were significantly associated with GlycA levels (P < 0.001 and P = 0.004, respectively). Initiation of biologic therapy (with anti-TNF treatment) reduced both psoriasis severity and GlycA levels significantly (P < 0.001 for both).⁵⁹

GlycA levels are responsive to lifestyle changes, with GlycA levels decreasing with weight loss (both from surgical intervention such as bariatric surgery, and from dietary change) as well as exercise. GlycA also decreases with use of anti-inflammatory medication.⁵² On the other hand, GlycA levels have been shown to be elevated in men performing night-shift work: in a cross-sectional study of people in the Lifelines Cohort Study (comparing 1000 night-shift workers, who had been had been working nights for 18.3 ± 10.5 years, to 1000 matched daytime workers), GlycA was higher in men working night-shift than days (P ∼ 0.00023).⁶¹

GlycA testing is currently available in the United States through a single commercial laboratory (LabCorp), which uses a cutoff value of ≥400 μmol/L as elevated.

Soluble Urokinase Plasminogen Activator Receptor

Soluble urokinase plasminogen activator receptor (suPAR) is a soluble form of the urokinase plasminogen activator receptor (uPAR, present on the surface membrane of immune cells and vascular endothelial cells), the activation of which is involved in tissue remodeling and T cell activation during an inflammatory response. suPAR is released into circulation as a signaling molecule during times of immune activation or inflammation, following enzymatic cleavage from the surface of immune cells. This cleavage results in the production of a variety of suPAR fragments or isoforms. As serum concentration of suPAR rise, this indicates a higher level of inflammation and immune system activation overall.^62
–64 Due to its solubility, suPAR is detectable in a range of body fluids, from serum to plasma, to saliva, urine, and cerebrospinal fluid (although it's not completely understood if specific suPAR isoforms may be enriched in one body fluid vs. another⁶⁵).

Levels of suPAR are positively correlated with CRP, IL-6, and TNFα.¹⁹ While both CRP and suPAR are independently predictive of disease risk, these two markers appear to reflect different aspects of inflammation. suPAR appears to better reflect endothelial dysfunction and subclinical organ damage than does CRP.⁶⁶ suPAR also appears to reflect chronic inflammation more than acute inflammation, with suPAR levels remaining largely unaffected by acute changes.^19,63

In healthy people, suPAR levels are low but detectable. In an analysis of samples from 9300 Danish adult blood donors (claiming to be healthy at time of donation, and donating voluntarily), median suPAR was 2.54 ng/mL in women (range 0.6–19.4), and 2.22 ng/mL in men (range 0.6–15.4), and levels increased with age in women and men alike (to a median of 2.71 ng/mL in women ages 51–65, and a median of 2.44 in men ages 51–65).²⁰ suPAR is subject to low within-person and circadian variability. It also has the advantage of being only weakly correlated with BMI, while CRP and BMI are strongly correlated.¹⁹

Higher levels of suPAR are seen in association with CVD, type 2 diabetes mellitus, cancer, infection, acute kidney injury, and chronic kidney disease.^63,64 suPAR also increases with aging, as mentioned above.⁶³ Adverse childhood experiences (ACEs) are also shown to be correlated with higher levels of suPAR in adulthood, to a stronger extent than CRP or IL-6.⁶³ Adolescents with higher risk scores for major depressive disorder (≥90th centile) have been demonstrated to have higher mean suPAR levels at age 18 than adolescents scoring as low risk (≤10th centile) (P < 0.001), supporting the concept that early-life depression may contribute to LGI.⁶⁷

Specific to CVD, not only does suPAR correlate significantly with cardiovascular events, but it also performs better than CRP as a CVD prognosticator. As suPAR levels increase, the risk of coronary artery calcification also increases, an effect that is more pronounced in men than women (OR 1.2, 95% CI 1.03–1.30, P = 0.02), and an effect not seen with CRP. Combining suPAR measurement with the Systematic Coronary Risk Evaluation model also improves prediction and classification of significant atherosclerosis in both men and women. suPAR has been shown to be independently associated with coronary flow reserve (a measure of coronary microvascular function) in people with non-obstructive CAD, while CRP was not.

suPAR also predicts the risk of CVD overall, with a HR of 1.7 in women and 2.1 in men for highest versus lowest tertiles (95% CI 1.1–2.8, P = 0.027 in women and 95% CI 1.4–3.2, P < 0.001 in men). Additionally, unlike other markers of inflammation, suPAR levels stay stable during acute MI and coronary artery bypass surgery.⁶⁸ And in patients with chronic HF, comparing the markers CRP, suPAR, and soluble suppression of tumorigenesis-2, only suPAR was predictive of 96-month mortality.⁶⁹

Regarding cancer and suPAR, in a 2017 systematic review and meta-analysis by Liu, Fan, and Wu, data from 12 studies was used to examine the association between circulating suPAR levels and survival in 2878 patients with cancer. This analysis showed a significantly poorer OS in patients with higher levels of suPAR for subgroups of people with colorectal cancer, breast cancer, ovarian cancer, and prostate cancer (total HR 1.63, 95% CI 1.46–1.81). The effect was most pronounced in those with colorectal cancer (HR 1.67, 95% CI 1.47–1.89).⁷⁰ In a 2022 systematic review by Paraskevas et al., 45 studies examining suPAR levels in people with cancer were assessed. suPAR was found to correlate with the diagnosis of cancer, poorer prognosis, reduced OS and PFS, and disease severity in people with a variety of cancer types (prostate, gastrointestinal, lung, ovarian). suPAR levels were also positively correlated with NLR; additionally, lower pretreatment suPAR levels were associated with better OS and treatment response in people with solid tumors receiving checkpoint inhibitors.⁷¹

The plasminogen activator system, of which uPAR is a central component, is key for numerous processes which are involved in inflammation and the mobilization of immunologically active cells. These include cell migration, adhesion, and chemotaxis. uPAR activation also plays an important role in the activation of metalloproteinases (enzymes that participate in the in proteolysis of extracellular matter). While these various processes are an important part of the healing process in inflammation, they are also central in cancer cell invasiveness and migration. For these reasons, suPAR is likely a key player in both cancer development and metastasis.⁷¹

suPAR levels may also serve as a valid marker of inflammation in autoimmunity, specifically in systemic lupus erythematosus (SLE). Because suPAR participates in leukocyte recruitment, helps regulate complement, and ensures effective efferocytosis (phagocytosis of dying cells), it seems plausible that it may participate in the pathogenesis of SLE (the development of which has been shown to involve dysregulation in the above-mentioned processes).⁷²

In a study of 198 people with SLE and 100 healthy blood donors, the relationship between suPAR levels and disease activity were assessed. Serum suPAR was significantly elevated in people with active SLE compared to healthy controls (P = 0.004). The Systemic Lupus International Collaborating Clinics/American College of Rheumatology damage index (SDI) was also significantly associated with suPAR levels in people with SLE (P < 0.0005). A significant effect was seen across several SDI domains, including ocular, skin, peripheral vascular, neuropsychiatric, and renal damage.⁷³ A 2020 study also indicated baseline suPAR is predictive of organ damage in people with SLE. In 344 subjects with SLE followed for five years, higher suPAR levels were seen in those with accrued organ damage, especially patients with SDI of ≥2 at the five-year timepoint (P = 0.004). In a logistic regression analysis as well as with adjustment for confounders, suPAR predicted SDI outcome (SDI ≥2; OR = 1.14; 95% CI 1.03–1.26). Examining specific SDI domains, higher baseline suPAR levels were seen in people who went on to develop musculoskeletal damage (P = 0.007).⁷⁴

suPAR levels also appear to be responsive to acute stress, and correlate with stressful life events overall. In one study, young adults (median age of 21.3 years; range 18–34 years) who were exposed to a laboratory psychological stressor experienced an acute rise in suPAR one hour post-stressor, from a baseline median suPAR of 1.75 ng/mL (range 0.5–8.0 ng/mL), to a post-stressor median level of 2.44 ng/mL (P < 0.0001). The increase in suPAR in response to acute stress paralleled the increase seen in TNF-α and IL-10, which also demonstrated 1.5-to-1.7-fold increases.⁶⁵

In another study of participants from the Dunedin Longitudinal Study (N = 828), the question of whether or not people who experienced more stressful life events during adulthood would demonstrate elevated suPAR when followed up in midlife at age 45 was explored. Participants with more stressful life events during ages 38 to 44 had higher suPAR at age 45 (P < 0.001) (an association which remained significant [P < 0.001] after controlling for sex, smoking status, BMI, and use of anti-inflammatory medications), and significantly greater increases in suPAR from baseline to age 45. By contrast, there was no association with change of CRP or IL-6 level for those with more stressful life events. Both adult stressors and ACEs were independently associated with suPAR level at age 45 as well (P < 0.001 for both). ACEs had an additive effect with adult stressors; people who had experienced ACEs had greater increases in suPAR level following stressful events in adulthood (P < 0.001), an effect which again remained consistent after controlling for sex, smoking status, BMI, and use of anti-inflammatory medications (also P < 0.001).⁷⁵

Clinical Relevance

Each of the inflammatory markers reviewed here may reflect slightly different aspects of the inflammatory process. How these markers might best be utilized in clinical practice remains an unanswered question. While in some cases these markers can be commercially tested (as is the case with GlycA), and in others they are not only readily available but also quite cost-effective (as is the case with NLR), some remain commercially unavailable and relegated to the realm of research only (suPAR).

In spite of this, a number of commonsense lifestyle or integrative medicine approaches that reduce inflammation have been demonstrated to impact one or more of these markers (seen in Table 4). There seems little to lose and much to gain by encouraging such healthy lifestyle practices or changes in our patients, as appropriate to the individual situation. Keep in mind as well that the table simply lists interventions for which research has been conducted demonstrating an impact or association. The absence of a specific mention in one category or another does not necessarily mean that an intervention does not impact a particular marker, but could simply mean that research has not been conducted in this area as of yet.

Table 4.

Clinical Strategies Shown to Impact Neutrophil-Lymphocyte Ratio, Glycoprotein Acetyls, or Soluble Urokinase Plasminogen Activator Receptor in the Reduction of Inflammation

Target	Approach	Rationale	Reference(s)
Maintain healthy glycemic control if diabetic	Target appropriate goal HbA1c and fasting blood sugar in pts with T2DM	Increased NLR is demonstrated to be associated with elevated HbA1c/poor glycemic control in people with T2DM; NLR can be utilized as a disease monitoring tool in pts with T2DM. Saliva suPAR levels are also higher in pts with poorly controlled T2DM.	Hussain et al.⁷⁶ Ali et al.⁷⁷
Optimize sleep	Address insomnia	Higher NLR is seen in people with increase sleep disturbance.	You et al.⁷⁸
	Address sleep apnea if present	NLR is significantly higher in pts with severe OSA compared to those with mild/moderate OSA or without OSA; continuous positive airway pressure use leads to significant reduction in NLR.	Shetty et al.⁷⁹ Friščić et al.⁸⁰
	Appropriate treatment of RLS	Meta-analysis shows association between RLS and higher NLR.	Jiménez-Jiménez et al.⁸¹
Manage stress	Address acute stressors	Saliva suPAR levels increase with acute psychological stress; higher suPAR levels seen in people with more stressful life events.	Fernandez-Botran et al.⁶⁵ Bourassa et al.⁷⁵
Manage stress	Acupuncture	Transcutaneous electrical acupoint stimulation shown to decrease cortisol and NLR.	Chi et al.⁸²
Exercise	Encourage regular physical activity	Regular exercise reduces NLR and GlycA; exercise training reduces NLR in people with cancer on active tx; high intensity interval training in people with autoimmune disease shown to decrease NLR; people with low levels of physical activity have 12.8% higher suPAR levels than those with healthy lifestyle/exercise; exercise reduces GlycA in people with prediabetes by targeting visceral adiposity.	Walzik et al.⁴⁷ Barber et al.⁸³ Salamon et al.⁸⁴ Joisten et al.⁸⁵ Haupt et al.⁸⁶ Bartlett et al.⁸⁷
Healthy diet	Maintain a healthy diet rich in plant foods and antioxidants	NLR is inversely associated with adherence to a Mediterranean diet pattern.	Bonaccio et al.⁸⁸
		Higher NLR is associated with low intake of vegetables, fruits, unprocessed meat, and fish, but with higher intakes of processed meat in the diet.	Hepsomali and Groeger⁸⁹
		Higher diet quality as evidenced by closer adherence to Healthy Eating Index (emphasizing daily consumption of fruits, vegetables, and whole grains, and minimizing consumption of sweets, processed meats, and snack foods) associated with lower NLR.	Rodríguez-Rodríguez et al.⁹⁰
		Total dietary antioxidant capacity is inversely associated with NLR in cancer survivors.	Alkan et al.⁹¹
		Trial period of vegan diet shown to lower GlycA in people with dyslipidemia.	Chiu et al.⁹²
Reduce toxin exposure(s)	Minimize exposure to pollution when able	Long-term residential exposure to moderate levels of particulate air pollution is associated with increased NLR.	Azzouz et al.⁹³
Reduce toxin exposure(s)	Quit smoking	Smoking cessation lowers plasma suPAR.	Eugen-Olsen et al.⁹⁴
Gut health	Improve diversity of gut flora; address dysbiosis if present	People with higher diversity of gut microbiota have lower NLR. Gut microbiome shown to modulate relationship between GlycA and menopause.	Yoon et al.⁹⁵ Bermingham et al.⁹⁶
Gut health	Probiotic/synbiotic may be considered if appropriate	Probiotics or synbiotics shown to reduce NLR in people undergoing oncologic surgery or with critical illness.	Rodríguez-Padilla et al.⁹⁷ Seifi et al.⁹⁸
Maintain healthy body weight	Lose weight if needed	Weight loss program reduces suPAR in people with coronary artery disease; weight loss program also reduces GlycA; weight loss from bariatric surgery results in reduced NLR.	Pedersen et al.⁹⁹ Collins et al.¹⁰⁰ Santos et al.¹⁰¹
Vitamin D status	Supplement vitamin D if required to either maintain sufficiency or correct deficiency	Vitamin D supplementation decreases NLR in people hospitalized with COVID, and in one study this resulted in reduced ICU admission and mortality; dietary fortification with vitamin D reduces NLR in people with abdominal obesity; vitamin D supplementation reduces NLR in adolescents.	Bychinin et al.¹⁰² Maghbooli et al.¹⁰³ Sharifan et al.¹⁰⁴ Tabatabaeizadeh et al.¹⁰⁵
Direct use of anti-inflammatory substances	Ginger	Ginger supplement reduces NLR in people with autoimmune disease.	Foshati et al.¹⁰⁶
	Omega 3 fatty acids	Fish oil supplementation reduces NLR in critically ill patients as well as in those undergoing cardiac surgery.	Kulkarni et al.¹⁰⁷ Yamamoto et al.¹⁰⁸
	Curcumin	Bioavailable curcumin supplementation shown to reduce NLR in the elderly.	Kishimoto et al.¹⁰⁹
	Hops	Supplementation with a xanthohumol extract from hops resulted in lower NLR in people admitted to the ICU with COVID. Individuals who received hops extract also had lower mortality.	Dabrowski et al.¹¹⁰
	Boswellia	A Boswellia extract enriched for boswellic acids decreases NLR in people hospitalized for moderate COVID.	Barzin Tond et al.¹¹¹
	Medicinal mushrooms	Supplementation with Ganoderma lucidum is associated with lower NLR and improved PFS and OS in breast and lung cancer patients receiving adjuvant chemotherapy.	Deng et al.¹¹²
Social support	Maintain good social support/connections	Feeling socially isolated and lonely shown to be associated with higher NLR.	Koyama et al.¹¹³
Maintain healthy dentition	Maintain regular dental and periodontal care	People with periodontitis have higher NLR as well as plasma and saliva suPAR levels; NLR also correlates with periodontitis severity.	Mishra et al.¹¹⁴ Lu et al.¹¹⁵ Sirin et al.¹¹⁶ Isola et al.¹¹⁷

GlycA, glycoprotein acetyls; HbA1c, hemoglobin A1c; ICU, intensive care unit; OSA, obstructive sleep apnea; RLS, restless leg syndrome; suPAR, soluble urokinase plasminogen activator receptor; T2DM, type 2 diabetes mellitus.

There is certainly a need for additional studies on these markers, including studies further examining the effects of therapeutics and lifestyle changes, which would lend insight into their clinical relevance. As with existing markers of inflammation utilized in clinical practice, results for these emerging markers would also need to be interpreted in the context of a complete clinical history. In spite of this, these new markers may offer distinct advantages compared to traditional measurements of CRP and ESR. How clinicians might best put these markers to use to serve the patient remains to be determined, but while waiting for clinical data to be produced, it seems there is little to lose by implementing practical lifestyle changes that address excess inflammation.

Footnotes

Author Disclosure Statement

No competing financial interests exist.

Funding Information

No funding was received for this article.▪

References

Siwan

, Twigg

, Min

. Alterations of CD163 expression in the complications of diabetes: A systematic review. J Diabetes Complications, 2022; 36:108150.

Arteaga-Henríquez

, Lugo-Marín

, Gisbert

, et al. Activation of the monocyte/macrophage system and abnormal blood levels of lymphocyte subpopulations in individuals with autism spectrum disorder: A systematic review and meta-analysis. Int J Mol Sci, 2022; 23:14329.

Farrell

, de Zoete

RMJ

, Cabot

, et al. Systemic inflammatory markers in neck pain: A systematic review with meta-analysis. Eur J Pain, 2020; 24:1666–1686.

Hamjane

, Benyahya

, Nourouti

, et al. Cardiovascular diseases and metabolic abnormalities associated with obesity: What is the role of inflammatory responses? A systematic review. Microvasc Res, 2020; 131:104023.

Speer

, Upton

, Semple

, et al. Systemic low-grade inflammation in post-traumatic stress disorder: a systematic review. J Inflamm Res, 2018; 11:111–121.

van den Munckhof

ICL

, Kurilshikov

, ter Horst

, et al. Role of gut microbiota in chronic low-grade inflammation as potential driver for atherosclerotic cardiovascular disease: a systematic review of human studies. Obes Rev, 2018; 19:1719–1734.

Werner

MCF

, Wirgenes

, Shadrin

, et al. Limited association between infections, autoimmune disease and genetic risk and immune activation in severe mental disorders. Prog Neuropsychopharmacol Biol Psychiatry, 2022; 116:110511.

Frazzei

, van Vollenhoven

, de Jong

, et al. Preclinical autoimmune disease: A comparison of rheumatoid arthritis, systemic lupus erythematosus, multiple sclerosis and type 1 diabetes. Front Immunol, 2022; 13:899372.

Taddei

, Caraccio

, Virdis

, et al. Low-grade systemic inflammation causes endothelial dysfunction in patients with Hashimoto's thyroiditis. J Clin Endocrinol Metab, 2006; 91:5076–5082.

10.

Martel

, Chang

, Ko

, et al. Gut barrier disruption and chronic disease. Trends Endocrinol Metab, 2022; 33:247–265.

11.

Libby

Inflammatory mechanisms: The molecular basis of inflammation and disease. Nutr Rev, 2007; 65(12 Pt 2):S140–S146.

12.

Chen

, Deng

, Cui

, et al. Inflammatory responses and inflammation-associated diseases in organs. Oncotarget, 2018; 9:7204.

13.

Grzybowski

, Sak

. A short history of the discovery of the erythrocyte sedimentation rate. Int J Lab Hematol, 2012; 34:442–444.

14.

Tishkowski

, Gupta

Erythrocyte Sedimentation Rate. Treasure Island, Florida: StatPearls Publishing; 2022.

15.

Yale

, Bray

, Bell

, et al. Erythrocyte sedimentation rate and C-reactive protein measurements and their relevance in clinical medicine. WMJ, 2016; 115:317–321.

16.

Assasi

, Blackhouse

, Campbell

, et al. Comparative Value of Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (CRP) Testing in Combination Versus Individually for the Diagnosis of Undifferentiated Patients With Suspected Inflammatory Disease or Serious Infection: A Systematic Review and Economic Analysis, 2015th ed. Ottawa, ON: Canadian Agency for Drugs and Technologies in Health, 2015.

17.

Brigden

The erythrocyte sedimentation rate: Still a helpful test when used judiciously. Postgrad Med, 1998; 103:257–274.

18.

Dinh

, Kaspersen

, Mikkelsen

, et al. Low-grade inflammation is negatively associated with physical Health-Related Quality of Life in healthy individuals: Results from The Danish Blood Donor Study (DBDS). PLoS One, 2019; 14:e0214468.

19.

Rasmussen

LJH

, Petersen

JEV

, Eugen-Olsen

. Soluble urokinase plasminogen activator receptor (suPAR) as a biomarker of systemic chronic inflammation. Front Immunol, 2021; 12:780641.

20.

Haastrup

, Grau

, Eugen-Olsen

, et al. Soluble urokinase plasminogen activator receptor as a marker for use of antidepressants. PLoS One, 2014; 9:e110555.

21.

Buonacera

, Stancanelli

, Colaci

, et al. Neutrophil to lymphocyte ratio: An emerging marker of the relationships between the immune system and diseases. Int J Mol Sci, 2022; 23:3636.

22.

Shahim

, Redfors

, Lindman

, et al. Neutrophil-to-lymphocyte ratios in patients undergoing aortic valve replacement: The PARTNER trials and registries. J Am Heart Assoc, 2022; 11:e024091.

23.

Zahorec

Neutrophil-to-lymphocyte ratio, past, present and future perspectives. Bratisl Lek Listy, 2021; 122:474–488.

24.

Faria

, Fernandes

, Silva

MJB

, et al. The neutrophil-to-lymphocyte ratio: a narrative review. Ecancermedicalscience, 2016; 10:702.

25.

Templeton

, McNamara

, Šeruga

, et al. Prognostic role of neutrophil-to-lymphocyte ratio in solid tumors: A systematic review and meta-analysis. J Natl Cancer Inst, 2014; 106:dju124.

26.

Bamias

, Merseburger

, Loriot

, et al. New prognostic model in patients with advanced urothelial carcinoma treated with second-line immune checkpoint inhibitors. J Immunother Cancer, 2023; 11:e005977.

27.

Chen

, Tang

, Xu

, et al. Inflammation-based prognostic scoring system for predicting the prognosis of advanced small cell lung cancer patients receiving anlotinib monotherapy. J Clin Lab Anal, 2022; 36:e24772.

28.

Chen

, Song

, Liang

, et al. Neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, and their variations as a basis for a prediction model in advanced NSCLC patients receiving anlotinib. Dis Markers, 2022; 2022:5879137.

29.

de Wit

, Wülfing

, Castellano

, et al. Baseline neutrophil-to-lymphocyte ratio as a predictive and prognostic biomarker in patients with metastatic castration-resistant prostate cancer treated with cabazitaxel versus abiraterone or enzalutamide in the CARD study. ESMO Open, 2021; 6:100241.

30.

Asano

, Kashiwagi

, Onoda

, et al. Predictive value of neutrophil/lymphocyte ratio for efficacy of preoperative chemotherapy in triple-negative breast cancer. Ann Surg Oncol, 2016; 23:1104–1110.

31.

Park

, Yeo

, Kim

, et al. Predictive roles of HER2 gene amplification and neutrophil-to-lymphocyte ratio on survival in HER2-positive advanced gastric cancer treated with trastuzumab-based chemotherapy. Am J Clin Oncol, 2021; 44:232–238.

32.

McLellan

, Henriques

, Ksontini

, et al. Prognostic value of the early change in neutrophil-to-lymphocyte ratio in metastatic pancreatic adenocarcinoma. Clin Res Hepatol Gastroenterol, 2021; 45:101541.

33.

Dell'Aquila

, Cremolini

, Zeppola

, et al. Prognostic and predictive role of neutrophil/lymphocytes ratio in metastatic colorectal cancer: a retrospective analysis of the TRIBE study by GONO. Ann Oncol, 2018; 29:924–930.

34.

Zhan

, Sun

, Hong

, et al. Combined detection of preoperative neutrophil-to-lymphocyte ratio and CEA as an independent prognostic factor in nonmetastatic patients undergoing colorectal cancer resection is superior to NLR or CEA alone. Biomed Res Int, 2017; 2017:3809464.

35.

Davison

, Takagi

, Edwards

, et al. Neutrophil-to-lymphocyte ratio and outcomes in patients admitted for acute heart failure (as seen in the BLAST-AHF, Pre-RELAX-AHF, and RELAX-AHF studies). Am J Cardiol, 2022; 180:72–80.

36.

Hashimoto

, Arimoto

, Narumi

, et al. The neutrophil-to-lymphocyte ratio predicts all-cause mortality in patients with implantable cardioverter defibrillators. Pacing Clin Electrophysiol, 2017; 40:135–144.

37.

Kim

, Heo

, Joo

, et al. Neutrophil-to-lymphocyte ratio as a predictor of short-term functional outcomes in acute ischemic stroke patients. Int J Environ Res Public Health, 2023; 20:898.

38.

Lin

, Dai

, Xu

, et al. Predictive value of neutrophil to lymphocyte ratio and red cell distribution width on death for ST segment elevation myocardial infarction. Sci Rep, 2021; 11:11506.

39.

, Ai

, Ni

, et al. The association between the neutrophil-to-lymphocyte ratio and mortality in patients with acute respiratory distress syndrome: A retrospective cohort study. Shock, 2019; 51:161–167.

40.

Mammen

, Kumar

, Thomas

, et al. Original research: Factors associated with mortality among moderate and severe patients with COVID-19 in India: A secondary analysis of a randomised controlled trial. BMJ Open, 2021; 11:50571.

41.

, Cheng

, Yang

, et al. Neutrophil-to-lymphocyte ratio as a predictive biomarker for moderate-severe ARDS in severe COVID-19 patients. Crit Care, 2020; 24:288.

42.

Maguire

, Richards

, Woods

, et al. The systemic inflammatory response and clinicopathological characteristics in patients admitted to hospital with COVID-19 infection: Comparison of 2 consecutive cohorts. PLoS One, 2021; 16:e0251924.

43.

Tadesse

, Bayissa

, Diriba

, et al. Neutrophil-to-lymphocyte ratio and cut-off values as predictor of severity and mortality in COVID-19 patients in millennium COVID-19 care center, Addis Ababa, Ethiopia. Int J Gen Med, 2022; 15:6739–6755.

44.

Lee

, Kim

, Na

, et al. Reference values of neutrophil-lymphocyte ratio, lymphocyte-monocyte ratio, platelet-lymphocyte ratio, and mean platelet volume in healthy adults in South Korea. Medicine (United States), 2018; 97:e11138.

45.

Song

, Graubard

, Rabkin

, et al. Neutrophil-to-lymphocyte ratio and mortality in the United States general population. Sci Rep, 2021; 11:464.

46.

, Chen

, Luo

, et al. Neutrophil-to-lymphocyte ratio positively correlates to age in healthy population. J Clin Lab Anal, 2015; 29:437–443.

47.

Walzik

, Joisten

, Zacher

, et al. Transferring clinically established immune inflammation markers into exercise physiology: focus on neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio and systemic immune-inflammation index. Eur J Appl Physiol, 2021; 121:1803–1814.

48.

Nieman

, Simondie

, Henson

, et al. Lymphocyte proliferative response to 2.5 hours of running. Int J Sports Med, 1995; 16:404–409.

49.

Sri Kaniganti

, Karigar Professor

, Chatterjee

, et al. NLR: An incipient marker to monitor inflammation, overtraining, and recovery in athletes. Int J Phys Educ Sports Health, 2022; 9:138–141.

50.

Howard

, Scheiner

, Kanetsky

, et al. Socio-demographic and lifestyle factors associated with the neutrophil-to-lymphocyte ratio. Ann Epidemiol, 2019; 38:11.

51.

Kourilovitch

, Galarza–Maldonado

. Could a simple biomarker as neutrophil-to-lymphocyte ratio reflect complex processes orchestrated by neutrophils?. J Transl Autoimmun, 2022; 100159.

52.

Ballout

, Remaley

. GlycA: A new biomarker for systemic inflammation and cardiovascular disease (CVD) risk assessment. J Lab Precis Med, 2020; 5:17.

53.

Otvos

, Shalaurova

, Wolak-Dinsmore

, et al. GlycA: A composite nuclear magnetic resonance biomarker of systemic inflammation. Clin Chem, 2015; 61:714–723.

54.

Mokkala

, Houttu

, Koivuniemi

, et al. GlycA, a novel marker for low grade inflammation, reflects gut microbiome diversity and is more accurate than high sensitive CRP in reflecting metabolomic profile. Metabolomics, 2020; 16:1–13.

55.

Akinkuolie

, Buring

, Ridker

, et al. A novel protein glycan biomarker and future cardiovascular disease events. J Am Heart Assoc, 2014; 3.

56.

Riggs

, Joshi

, Khera

, et al. GlycA, hsCRP differentially associated with MI, ischemic stroke: In the Dallas Heart Study and Multi-Ethnic Study of Atherosclerosis: GlycA, hsCRP differentially associated MI, stroke. Am J Prev Cardiol, 2022; 12:100373.

57.

Jang

, Ogunmoroti

, Ndumele

, et al. Association of the novel inflammatory marker GlycA and incident heart failure and its subtypes of preserved and reduced ejection fraction: The multi-ethnic study of atherosclerosis. Circ Heart Fail, 2020; 13(8):e007067.

58.

Muhlestein

, May

, Galenko

, et al. GlycA and hsCRP are independent and additive predictors of future cardiovascular events among patients undergoing angiography: The intermountain heart collaborative study. Am Heart J, 2018; 202:27–32.

59.

Joshi

, Lerman

, Aberra

, et al. GlycA is a novel biomarker of inflammation and subclinical cardiovascular disease in psoriasis. Circ Res, 2016; 119:1242–1253.

60.

Ritchie

, Würtz

, Nath

, et al. The biomarker GlycA is associated with chronic inflammation and predicts long-term risk of severe infection. Cell Syst, 2015; 1:293–301.

61.

Bizzarri

, Dollé

MET

, Loef

, et al. GlycA, a biomarker of low-grade inflammation, is increased in male night shift workers. Metabolites, 2022; 12:1172.

62.

Benucci

, Damiani

, Russo

, et al. The association of uPA, uPAR, and suPAR system with inflammation and joint damage in rheumatoid arthritis: suPAR as a biomarker in the light of a personalized medicine perspective. J Pers Med, 2022; 12:1984.

63.

Rasmussen

LJH

, Caspi

, Ambler

, et al. Association between elevated suPAR, a new biomarker of inflammation, and accelerated aging. J Gerontol A, 2021; 76:318–327.

64.

Sudhini

, Wei

, Reiser

. suPAR: An inflammatory mediator for kidneys. Kidney Dis, 2022; 8:265.

65.

Fernandez-Botran

, Szabo

, Lyle

, et al. The levels of soluble urokinase plasminogen activator receptor (suPAR) in saliva are influenced by acute stress. Biol Psychol, 2021; 165:108147.

66.

Lyngbæk

, Sehestedt

, Marott

, et al. CRP and suPAR are differently related to anthropometry and subclinical organ damage. Int J Cardiol, 2013; 167:781–785.

67.

Latham

, Kieling

, Arseneault

, et al. Longitudinal associations between adolescents' individualised risk for depression and inflammation in a UK cohort study. Brain Behav Immun, 2022; 101:78.

68.

Hodges

, Bang

, Wachtell

, et al. SuPAR: A new biomarker for cardiovascular disease?. Can J Cardiol, 2015; 31:1293–1302.

69.

Dupuy

, Kuster

, Bargnoux

, et al. Long term pronostic value of suPAR in chronic heart failure: reclassification of patients with low MAGGIC score. Clin Chem Lab Med, 2021; 59:1299–1306.

70.

Liu

, Fan

, Wu

. Prognostic role of circulating soluble uPAR in various cancers: A systematic review and meta-analysis. Clin Lab, 2017; 63:871–880.

71.

Paraskevas

, Mulita

, Michailides

, et al. The role of soluble urokinase plasminogen activator receptor (suPAR) in patients with cancer: a review of the current literature. Med Glas (Zenica), 2022; 19:197–206.

72.

Enocsson

, Sjöwall

, Wetterö

. Soluble urokinase plasminogen activator receptor—A valuable biomarker in systemic lupus erythematosus?. Clin Chim Acta, 2015; 444:234–241.

73.

Enocsson

, Wetterö

, Skogh

, et al. Soluble urokinase plasminogen activator receptor levels reflect organ damage in systemic lupus erythematosus. Transl Res, 2013; 162:287–296.

74.

Enocsson

, Wirestam

, Dahle

, et al. Soluble urokinase plasminogen activator receptor (suPAR) levels predict damage accrual in patients with recent-onset systemic lupus erythematosus. J Autoimmun, 2020; 106:102340.

75.

Bourassa

, Rasmussen

LJH

, Danese

, et al. Linking stressful life events and chronic inflammation using suPAR (soluble urokinase plasminogen activator receptor). Brain Behav Immun, 2021; 97:79–88.

76.

Hussain

, Babar

MZM

, Akhtar

, et al. Neutrophil lymphocyte ratio (NLR): A well assessment tool of glycemic control in type 2 diabetic patients. Pak J Med Sci, 2017; 33:1366.

77.

Ali

, Qasem

, Baskaradoss

. Periodontal clinicoradiographic status and whole saliva soluble urokinase plasminogen activation receptor and tumor necrosis factor alpha levels in type-2 diabetic and non-diabetic individuals. Oral Health Prev Dent, 2021; 19:481–488.

78.

You

, Chen

, Fang

, et al. The association between sedentary behavior, exercise, and sleep disturbance: A mediation analysis of inflammatory biomarkers. Front Immunol, 2022; 13:1080782.

79.

Shetty

, Chandrashekhar

, Chaya

, et al. Role of neutrophil to lymphocyte ratio in predicting severity of obstructive sleep apnea. Indian J Otolaryngol Head Neck Surg, 2022; 74:5003–5007.

80.

Friščić

, Perčić

, Vidović

, et al. Impact of CPAP therapy on new inflammation biomarkers. J Clin Med, 2022; 11.

81.

Jiménez-Jiménez

, Alonso-Navarro

, García-Martín

, et al. Inflammatory factors and restless legs syndrome: A systematic review and meta-analysis. Sleep Med Rev, 2023; 68:101744.

82.

Chi

, Zhang

, Yang

, et al. Transcutaneous electrical acupoint stimulation for improving postoperative recovery, reducing stress and inflammatory responses in elderly patient undergoing knee surgery. Am J Chin Med, 2019; 47:1445–1458.

83.

Barber

, Kraus

, Church

, et al. Effects of regular endurance exercise on GlycA: Combined analysis of 14 exercise interventions. Atherosclerosis, 2018; 277:1–6.

84.

Salamon

, Dougherty

, Whiting

, et al. Effects of a prescribed, supervised exercise programme on tumour disease progression in oncology patients undergoing anti-cancer therapy: A retrospective observational cohort study. Intern Med J, 2023; 53:104–111.

85.

Joisten

, Proschinger

, Rademacher

, et al. High-intensity interval training reduces neutrophil-to-lymphocyte ratio in persons with multiple sclerosis during inpatient rehabilitation. Mult Scler, 2021; 27:1136–1139.

86.

Haupt

, Rasmussen

LJH

, Kallemose

, et al. Healthy lifestyles reduce suPAR and mortality in a Danish general population study. Immun Ageing, 2019; 16:1.

87.

Bartlett

, Slentz

, Connelly

, et al. Association of the composite inflammatory biomarker GlycA, with exercise-induced changes in body habitus in men and women with prediabetes. Oxid Med Cell Longev, 2017; 2017:5608287.

88.

Bonaccio

, Di Castelnuovo

, De Curtis

, et al. Adherence to the Mediterranean diet is associated with lower platelet and leukocyte counts: Results from the Moli-sani study. Blood, 2014; 123:3037–3044.

89.

Hepsomali

, Groeger

. Examining the role of systemic chronic inflammation in diet and sleep relationship. J Psychopharmacol, 2022; 36:1077.

90.

Rodríguez-Rodríguez

, López-Sobaler

, Ortega

, et al. Association between neutrophil-to-lymphocyte ratio with abdominal obesity and healthy eating index in a representative older Spanish population. Nutrients, 2020; 12:855.

91.

Alkan ŞB, Artaç

, Rakıcıoğlu

. Dietary antioxidant capacity and serum inflammatory biomarkers levels in cancer survivors. Nutr Cancer, 2022; 74:1243–1251.

92.

Chiu

THT

, Kao

, Wang

, et al. A dietitian-led vegan program may improve GlycA, and other novel and traditional cardiometabolic risk factors in patients with dyslipidemia: A pilot study. Front Nutr, 2022; 9:807810.

93.

Azzouz

, Xu

, Barregard

, et al. Air pollution and biomarkers of cardiovascular disease and inflammation in the Malmö diet and cancer cohort. Environ Health, 2022; 21:39.

94.

Eugen-Olsen

, Ladelund

, Sørensen

. Plasma suPAR is lowered by smoking cessation: A randomized controlled study. Eur J Clin Invest, 2016; 46:305–311.

95.

Yoon

, Kim

, Lee

, et al. Association between neutrophil-to-lymphocyte ratio and gut microbiota in a large population: A retrospective cross-sectional study. Sci Rep, 2018; 8:1–9.

96.

Bermingham

, Linenberg

, Hall

, et al. Menopause is associated with postprandial metabolism, metabolic health and lifestyle: The ZOE PREDICT study. EBioMedicine, 2022; 85:104303.

97.

Rodríguez-Padilla Á, Morales-Martín

, Pérez-Quintero

, et al. Serological biomarkers and diversion colitis: Changes after stimulation with probiotics. Biomolecules, 2021; 11:684.

98.

Seifi

, Sedaghat

, Nematy

, et al. Effects of synbiotic supplementation on the serum endotoxin level, inflammatory status, and clinical outcomes of adult patients with critical illness: A randomized controlled trial. Nutr Clin Pract, 2022; 37:451–458.

99.

Pedersen

, Olsen

, Anholm

, et al. Effects of 1 year of exercise training versus combined exercise training and weight loss on body composition, low-grade inflammation and lipids in overweight patients with coronary artery disease: a randomized trial. Cardiovasc Diabetol, 2019; 18:127.

100.

Collins

, Kraus

, Rogers

, et al. Effect of behavioral weight-loss program on biomarkers of cardiometabolic disease risk: Heart Health Study randomized trial. Obesity (Silver Spring), 2023; 31:338–349.

101.

Santos

, Salgado

, Santos

, et al. Effect of bariatric surgery on weight loss, inflammation, iron metabolism, and lipid profile. Scand J Surg, 2014; 103:21–25.

102.

Bychinin

, Klypa

, Mandel

, et al. Effect of vitamin D3 supplementation on cellular immunity and inflammatory markers in COVID-19 patients admitted to the ICU. Sci Rep, 2022; 12:18604.

103.

Maghbooli

, Sahraian

, Jamalimoghadamsiahkali

, et al. Treatment with 25-hydroxyvitamin D3 (calcifediol) is associated with a reduction in the blood neutrophil-to-lymphocyte ratio marker of disease severity in hospitalized patients with COVID-19: A pilot multicenter, randomized, placebo-controlled, double-blinded clinical trial. Endocr Pract, 2021; 27:1242–1251.

104.

Sharifan

, Rashidmayvan

, Khorasanchi

, et al. Efficacy of low-fat milk and yogurt fortified with vitamin D3 on systemic inflammation in adults with abdominal obesity. J Health Popul Nutr, 2022; 41:8.

105.

Tabatabaeizadeh

, Avan

, Bahrami

, et al. High dose supplementation of vitamin D affects measures of systemic inflammation: reductions in high sensitivity C-reactive protein level and neutrophil to lymphocyte ratio (NLR) distribution. J Cell Biochem, 2017; 118:4317–4322.

106.

Foshati

, Poursadeghfard

, Heidari

, et al. The effect of ginger (Zingiber officinale) supplementation on clinical, biochemical, and anthropometric parameters in patients with multiple sclerosis: a double-blind randomized controlled trial. Food Funct, 2023; 14:3701–3711.

107.

Kulkarni

A V.

, Anand

, Vyas

, et al. Omega-3 fatty acid lipid emulsions are safe and effective in reducing endotoxemia and sepsis in acute-on-chronic liver failure: An open-label randomized controlled trial. J Gastroenterol Hepatol, 2021; 36:1953–1961.

108.

Yamamoto

, Kajikawa

, Otani

, et al. Protective effect of eicosapentaenoic acid on insulin resistance in hyperlipidemic patients and on the postoperative course of cardiac surgery patients: the possible involvement of adiponectin. Acta Med Okayama, 2014; 68:349–361.

109.

Kishimoto

, Imaizumi

, Wada

, et al. Newly developed highly bioavailable curcumin formulation, curcuRougeTM, reduces neutrophil/lymphocyte ratio in the elderly: A double-blind, placebo-controlled clinical trial. J Nutr Sci Vitaminol (Tokyo), 2021; 67:249–252.

110.

Dabrowski

, Gagos

, Siwicka-Gieroba

, et al. Humulus lupus extract rich in xanthohumol improves the clinical course in critically ill COVID-19 patients. Biomed Pharmacother, 2023; 158:114082.

111.

Barzin Tond

, Balenci

, Khajavirad

, et al. Inflawell® improves neutrophil-to-lymphocyte ratio and shortens hospitalization in patients with moderate COVID-19, in a randomized double-blind placebo-controlled clinical trial. Inflammopharmacology, 2022; 30:465–475.

112.

Deng

, Ma

, Tang

, et al. Dynamic biomarkers indicate the immunological benefits provided by Ganoderma spore powder in post-operative breast and lung cancer patients. Clin Transl Oncol, 2021; 23:1481–1490.

113.

Koyama

, Nawa

, Yamaoka

, et al. Interplay between social isolation and loneliness and chronic systemic inflammation during the COVID-19 pandemic in Japan: Results from U-CORONA study. Brain Behav Immun, 2021; 94:51–59.

114.

Mishra

, Gazala

, Rahman

. Clinical and diagnostic significance of blood leukocyte ratios in young patients with stage III grade C periodontitis. Acta Odontol Scand, 2022; 80:161–168.

115.

, Li

, Wang

, et al. Elevated neutrophil-to-lymphocyte ratio but not platelet-to-lymphocyte ratio is associated with generalized aggressive periodontitis in a Chinese population. J Periodontol, 2021; 92:507–513.

116.

Sirin

, Ozcelik

, Uzun

, et al. Association between C-reactive protein, neutrophil to lymphocyte ratio and the burden of apical periodontitis: A case-control study. Acta Odontol Scand, 2019; 77:142–149.

117.

Isola

, Polizzi

, Alibrandi

, et al. Independent impact of periodontitis and cardiovascular disease on elevated soluble urokinase-type plasminogen activator receptor (suPAR) levels. J Periodontol, 2021; 92:896–906.