Biomarkers as point of care tests (POCT) in neonatal sepsis: A state of science review

Abstract

Lack of a standard definition of neonatal sepsis and a swift diagnostic method has proven detrimental in the management of this serious condition. Biomarkers have emerged as a beacon that might help us detect neonatal sepsis more effectively. The use of point-of-care biomarkers can aid in early diagnosis and timely initiation of treatment. Procalcitonin, presepsin, interleukin-6, highly specific C-reactive protein, and neutrophil gelatinase-associated lipocalin have been proven to aid in early diagnosis and timely initiation of treatment, thereby reducing sepsis-induced morbidity and mortality. These biomarkers have been found to be useful in reducing the duration of hospital stay and monitoring the response to therapy. When used in combination with each other, or with clinical scores, they have been proven to be advantageous over the gold standard by eliminating the waiting time for blood culture results. The use of biomarkers as a point of care investigation holds a future over the traditional method. We present a state of science review of literature summarizing the current status of these biomarkers in neonatal sepsis.

Keywords

Biomarkers neonatal sepsis point-of-care testing procalcitonin presepsin highly specific CRP IL-6

1 Introduction

Neonatal sepsis is the most common cause of neonatal deaths worldwide, with incidence varying from 1 to 4 cases per 1000 live births in developed countries to 30 per 1000 live births in a developing country like India [1, 2]. Neonatal sepsis presents within the first 28 days of life, with early-onset neonatal sepsis (EONS) presenting within 72 hours (hr) of birth, usually with respiratory distress; and late-onset neonatal sepsis (LONS), presenting after 72 hr of birth [1]. Positive blood culture is the gold standard for definitive diagnosis of neonatal sepsis. However, this requires the infant to be identified with clinical signs of systemic inflammatory response syndrome (SIRS) in order to be evaluated. Furthermore, the possibility of contamination of the blood sample must also be ruled out [3]. Blood culture is time-consuming, usually taking 24 to 48 hr for reporting the growth of an organism. The growth also depends on the amount of blood used for culture, with a small amount of blood leading to decreased frequency of detection [4]. Therefore, a much faster and more refined diagnostic method is required for timely management of neonatal sepsis.

In this expedition for finding a suitable diagnostic method, biomarkers have emerged as a beacon that might help us detect neonatal sepsis more effectively. They have been evaluated in multiple studies globally with varied results. These biomarkers can be divided into four groups: acute-phase proteins, cell surface antigens, cytokines and chemokines, and soluble adhesion molecules. An ideal biomarker should have both a high sensitivity as well as a high specificity, the former being more important in order to avoid missing cases due to erratic clinical presentations [1].

Point-of-care testing (POCT) refers to any kind of test that is performed near the patient and can provide rapid results. These tests have been implemented in a variety of diseases, and have shown to decrease treatment delays, improve outcomes, increase timely discharges, and the total length of stay. POCT has been shown to reduce delays to treatment initiation in the critically ill, improve outcomes, increase timely patient discharge rates, and decrease total length of stay. The accelerated patient flow seems to outweigh the elevated costs of POCT per analysis when used effectively [5].

With the increasing availability of POCT and new studies on the use of biomarkers for neonatal sepsis, we might be able to decrease neonatal morbidity due to sepsis, by early detection and guided antibiotic therapy. We discuss some of these biomarkers that are available as POCT and can be of promising value in neonatal sepsis.

1.1 Procalcitonin

Procalcitonin (PCT) is a 116-amino acid protein, that is produced by the parafollicular C cells of the thyroid gland and then converted to calcitonin in order to maintain calcium homeostasis. It is also an acute-phase reactant that gets produced in response to inflammation, with a half-life of 24–30 hr. During an inflammatory reaction, procalcitonin was found to be produced by sites other than the thyroid gland, acting as a chemoattractant for monocytes in blood [6, 7].

In 2011, Vouloumanou et al. conducted a meta-analysis of 16 studies (involving 1959 neonates) evaluating PCT levels in neonates with culture-proven or clinically diagnosed sepsis and compared them with those in neonates with other conditions. The pooled (95% CI) sensitivity and specificity were 81% (74–87%) and 79% (69–87%), respectively. The area under the hierarchical summary receiver operating characteristic (HSROC) curve (AUC) was 0.87. They also observed that the diagnostic accuracy of procalcitonin was greater in case of LONS (AUC: 0.95) than for EONS (AUC:0.78) [8]. Another meta-analysis, performed by Pontrelli et al. in 2017, included 17 studies and assessed the accuracy of procalcitonin for diagnosis of sepsis in neonates and children with SIRS. It comprised of 1408 patients (1086 neonates and 322 children). In the neonatal group, they observed a moderate accuracy for diagnosis of sepsis with a sensitivity of 85% (CI: 76–90%) and a specificity of 54% (CI: 38–70%) at the PCT cut-off of 2.0–2.5 ng/mL [6]. A multicentre, randomized controlled trial called Neonatal Procalcitonin Intervention Study (NeoPIns) was conducted by Stocker et al. on suspected EONS cases to prove the effectiveness of biomarker-guided antibiotic therapy. Out of 1710 neonates, 866 were randomly assigned to the procalcitonin-guided therapy group and 844 to the standard therapy group. The duration of antibiotic therapy was significantly reduced in the procalcitonin group (intention to treat: 55·1 vs 65·0 hr, p < 0·0001; per protocol: 51·8 vs 64·0 hr, p < 0·0001). However, they were unable to establish non-inferiority for re-infection or death due to the low occurrence of re-infections and non-occurrence of deaths [9].

B·R·A·H·M·S PCT direct is the first high sensitive point-of-care test (POCT), that can measure procalcitonin levels in capillary or venous blood samples quickly. A prospective, comparison study conducted in three European emergency departments including 303 patients, over a 6-month period, found a high diagnostic accuracy and faster time to result (25 vs 144 min, difference 119 min, 95% CI 110–134 min, p < 0.0001) of B·R·A·H·M·S PCT direct as compared to the reference methods. This reduced the time to start treatment [10].

1.2 Presepsin

Presepsin, also known as soluble CD14 subtype (sCD14-ST), is produced by membranous CD14 detachment or by cell secretion. It is a 13-kDa N-terminal fragment of soluble CD14 with a half-life of about 4–6 hr [11, 12]. Its increasing levels in the circulation after the onset of sepsis may indicate systemic inflammation [13].

Poggi et al. in their prospective single-center study of presepsin levels in preterm babies with LONS, showed that the levels of presepsin, PCT, and CRP decreased significantly on days three and five. However, only presepsin showed a reduction on day one, suggesting it to be useful for monitoring response to therapy as compared to the other markers [14]. Mussap et al. performed a prospective observational study involving 65 critically ill full-term and preterm newborns and divided them into three groups; culture-positive sepsis, culture-negative sepsis, and neonates with no clinical signs or bacteriological evidence of sepsis. Presepsin levels were found to be significantly higher in bacterial sepsis as well as non-bacterial SIRS group as compared to the controls (p < 0.0001). However, no statistically significant difference was found between bacterial sepsis and non-bacterial SIRS (p = 0.730). A blood presepsin of 540 ng/L offered the best sensitivity (100%), but moderate specificity of 81.2% for monitoring the course of the disease and response to treatment. When the cut-off was readjusted to 600 ng/L, the specificity improved to 100% [11]. Ozdemir et al. evaluated the efficacy of presepsin for the diagnosis and follow-up of EONS and found that the presepsin levels of sepsis group at zero hr were significantly higher (704.27±223.54 pg/mL) than the control group (508.33±165.46 pg/mL). The cut-off value for presepsin was 539 pg/mL with an area under the curve of 0.772. The sensitivity of CRP, PCT, and presepsin at zero hour was found to be 83, 67, and 80%, whereas the specificity was found to be 75, 67, and 75%, respectively [13]. High diagnostic accuracy was observed at a cut-off of 823 ng/mL in neonates with late-onset sepsis [15]. A recent meta-analysis and systemic review concluded that presepsin alone can be used to diagnose and rule out neonatal sepsis with high sensitivity and specificity. It performed better than CRP and PCT for monitoring response to treatment [16].

Okamura et al. developed an automated presepsin assay system (PATHFAST) based on chemiluminescent enzyme immunoassay (CLEIA) principle. They studied the performance of the system by measuring presepsin concentrations in adults having sepsis, which were found to be significantly higher than those in healthy adults [17].

1.3 Highly specific CRP (hsCRP)

C-reactive protein is an acute-phase reactant that is produced in the liver and then secreted into the plasma, after being induced by IL-6 during an inflammatory response or tissue injury. It has a half-life of 24–48 hr and is one of the most commonly used markers in medical settings [18, 19]. Highly sensitive CRP (hsCRP) is a high sensitivity quantification compared to the standard CRP for the diagnosis of neonatal sepsis. It has a lower cut-off than the conventional assays, with the value of hsCRP < 1 mg/L having increased sensitivity for neonatal infection [19].

Rashwan et al. conducted a cross-sectional study on 168 neonates to assess the diagnostic and prognostic values of hsCRP, CRP, PCT, presepsin, and IL-6, separately and in combination. They observed significantly higher serum levels of hsCRP and presepsin in EONS cases as compared to LONS, and in the proven versus probable sepsis group (p < 0.05 for all). The combination of hsCRP and PCT together with either IL-6 or presepsin (especially in EONS) was a better predictor for neonatal sepsis. However, none of the markers were found to be effective enough to diagnose or rule out neonatal sepsis on their own [20]. A prospective study including 40 neonates with clinically suspected sepsis and 40 control neonates evaluated hsCRP, CRP, and IL-6 as early markers of sepsis and compared them to blood culture. They were able to stratify the risk of infection on the basis of hsCRP values,<0.5 mg/L indicating no risk of infection, 0.5–1 mg/L indicating low risk, 1–3 mg/L indicating average risk, and > 3 mg/L indicating high risk. However, despite having a high sensitivity, it was found to be a less reliable marker on its own [21]. Wu et al. assessed the predictive value of joint detection of hsCRP, PCT, and Serum Amyloid A (SAA) in the detection of neonatal sepsis in 195 cases with neonatal sepsis and 100 controls. The levels were significantly higher in the former before treatment. The area under the curve, sensitivity (92%), and specificity (75.38%) were found to be better when all three markers were combined together, as compared to individual detection, thereby concluding that the joint detection of hsCRP, PCT, and SAA has high diagnostic value in neonatal sepsis [22].

BodiTech Med Inc. developed a fluorescence-based immunochromatographic method for measuring hsCRP concentrations in blood. They used 150 samples from healthy adults and compared the hsCRP concentrations determined by the iChroma reader with serum hsCRP levels in turbidimetric assay on TBA 200FR and in nephelometric assay on the BN II analyzer. The readings were found to be comparable to the other methods and suitable for POCT in the detection and quantification of hsCRP [18].

1.4 Interleukin-6 (IL-6)

Interleukin-6 is a cytokine, composed of 184 amino acids, that is produced by lymphoid cells such as B cells, T cells, and monocytes; non-lymphoid cells such as fibroblasts, keratinocytes, endothelial cells, mesangial cells, and various tumor cells. It is known to regulate immune responses and acute phase reactions and plays a part in hematopoiesis as well [23]. It has a very short half-life of about an hour and its levels become undetectable within 24 hr following initiation of antimicrobial treatment [7, 23]. This can be used to detect cases at an early stage [19]. Combining its use with other biomarkers might improve its efficacy in the diagnosis of neonatal sepsis and monitoring response to treatment.

A meta-analysis was performed by Shahkar et al. on 13 studies including 353 septic neonates and 691 controls to assess the validity of IL-6 for neonatal sepsis. The pooled sensitivity was found to be 79% and pooled specificity was 84%, while the maximum joint sensitivity and specificity (Q value) in the Summary ROC curve was 82% with AUC of 0.89 (95% CI: 0.84–0.94). Furthermore, the diagnostic accuracy of IL-6 was not affected by study quality, cut-off levels of IL-6 assay, birth-weight of neonates, and control group status [24]. On the contrary, variable sensitivity and specificity were reported by Hedegaard et al., being high at zero hour and lower after 24 and 48 hr [1]. Ganesan et al. showed that the combination of IL-6 and CRP had high sensitivity and low negative predictive value as compared to the other biomarkers. The CRP level > 13.49 mg/L showed sensitivity and specificity of 80% and 65.70% respectively and IL–6 > 51.29 pg/mL showed sensitivity and specificity of 100% and 62.86%, respectively. The combination of IL-6 and CRP showed a sensitivity and specificity of 100% and 75.71%, respectively, and therefore were observed to be better predictors of neonatal sepsis [21].

Huang et al. developed a kit for quantitatively detecting IL-6 in the serum using a double-antibody sandwich immunofluorescent assay based on europium nanoparticles (Eu-np) combined with lateral flow immunoassay (LFIA). They evaluated its performance by using 214 serum samples and compared the results with a Siemens CLIA IL-6 kit, which showed a high correlation. Furthermore, it yielded results within 15 min, thereby being suitable for point of care testing of IL-6 [23]. Fischer et al. along with Proxim, CA, USA, also developed a quantitative IL-6 assay that operates using disposable cartridges, having an immunoelectrochemical sensor and a lyophilized bead with reporter antibodies. Being a handheld device that yields results within 15–20 min, it is ideal for bedside use. Its performance was assessed using 56 samples and the results correlated excellently with other assays like ELISA, Ella (Automated Microfluidic Immunoassay), and Roche Cobas (Automated Sandwich Immunoassay) [25].

1.5 Neutrophil gelatinase-associated lipocalin (NGAL)

Neutrophil gelatinase-associated lipocalin, also known as Lipocalin 2, is a 24kDA protein that was initially described as an oncogene produced in various tissues such as kidneys, bone marrow, uterus, salivary gland, stomach, appendix, colon, trachea, and lungs of adults, and in fetal spleen and lungs. It is also present in the specific granules of neutrophils and takes part in the immune response to inflammation [26]. It is rapidly eliminated from circulation by the kidney and its half-life is about 10–20 min. Increased levels of NGAL in serum and urine have been increasingly used as a marker of acute kidney injury (AKI). However, NGAL levels can’t be solely used as a marker of AKI in newborns, as equally elevated levels of serum and urinary NGAL were seen in septic neonates with and without AKI, in a study conducted by Smertka et al. They also observed that NGAL levels strongly correlate with CRP and PCT, and therefore considered it to be a marker of endothelial injury and neutrophil activation [27]. Further studies are required to assess the efficacy of NGAL measurement in diagnosis and monitoring of neonatal sepsis, alone as well as in conjunction with other biomarkers. Multiple POCT kits are available for measuring NGAL levels. Up converting phosphor technology-based lateral flow assay (UPT-LFA) was developed to measure NGAL levels in serum and urine for detecting AKI. It only takes 30 min as compared to four hours with ELISA. Lei et al. compared it with ELISA for serum samples and with Nanjing Norman Biological Technology enhanced immunoturbidimetric assay (NORMAN Diagnostics Division, Nanjing) for urine samples. They observed that the UPT-LFA was consistent with the immunoturbidimetry assay, having positive and negative coincidence rates of 97.92 % and 92.73 %, respectively. Correlative regression analysis showed that the concordance rate between UPT-LFA and ELISA was also high (R² = 0.95) [28].

Table 1 summarizes the studies that have evaluated the role of these biomarkers for the diagnosis of neonatal sepsis.

Table 1
Summary of studies investigating serum PCT, presepsin, hsCRP, IL-6 and NGAL in neonatal sepsis

Author Type of study Biomarker/Intervention (if any) Study population Result

Vouloumanou et al. [8] Systematic Review and Meta-analysis PCT 16 studies (1,959 neonates) Pooled (95% CI) sensitivity and specificity were 81% (74–87) and 79% (69–87); Diagnostic accuracy was more for LONS (AUC: 0.95), than for EONS (AUC: 0.78)

Pontrelli et al. [6] Systematic Review and Meta-analysis PCT 17 studies (1,086 neonates and 322 children) Sensitivity was 85%, (CI: 76–90%) and specificity was 54 (CI: 38–70%) at a cut-off of 2.0–2.5 ng/mL

Stocker et al. [9] Randomised Controlled Intervention Trial PCT PCT guided antibiotic therapy vs standard care antibiotic therapy 1710 neonates with sepsis (866 in PCT guided therapy group and 844 in standard therapy group) Duration of therapy was significantly reduced in PCT-guided therapy group (51·8 vs 64·0 h); Length of hospital stay was also shorter in PCT-guided therapy group

Poggi et al. [14] Prospective study Presepsin Measured presepsin levels at days 0, 1, 3 and 5, along with CRP and PCT levels 40 preterm neonates ≤32 weeks gestation (19 with LOS and 21 non-infected controls) Presepsin was higher in LOS group than control group; Presepsin showed borderline reduction on day 1 following therapy; Presepsin, PCT and CRP showed significant reduction on days 3 and 5

Mussap et al. [11] Prospective study Presepsin Measured presepsin levels at days 0 and 3 65 full term and preterm neonates (25 with bacterial sepsis, 15 with non-bacterial SIRS and 25 non-infected controls) Significantly higher presepsin levels in bacterial sepsis than control; Significantly higher presepsin levels in non-bacterial SIRS group than control; No significant difference between levels in bacterial sepsis and non-bacterial SIRS; Recommended a presepsin cut-off of 600 ng/L for neonatal sepsis

Ozdemir et al. [13] Prospective study Presepsin Measured presepsin levels in neonates with EOS and healthy controls and compared effectiveness with PCT and CRP 69 term neonates (29 with EOS and 40 healthy controls) Presepsin levels were significantly higher in EOS group at T0; Cut-off value for presepsin was 539 pg/mL with AUC of 0.772; Sensitivities of CRP, PCT, and presepsin at 0 hour were 83, 67, and 80%, whereas the specificities were 75, 67, and 75%, respectively

Degirmencioglu et al. [15] Prospective study Presepsin Measured levels of Presepsin, Fetuin A, CRP and IL-6 at days 0, 3 and 7 of diagnosis 55preterm neonates ≤32 weeks gestation (26 with culture proven LOS and 29 controls) Presepsin was found to have 88.9% sensitivity, 88.9% specificity and AUC of 0.939 at cut-off of 823 ng/mL for culture-proven LOS

Ruan et al. [16] Systematic Review and Meta-analysis Presepsin, PCT, CRP and combination of PCT+CRP- 28 studies (2661 neonates) Presepsin alone or a combination of PCT+CRP improve the accuracy of diagnosis of neonatal sepsis; AUC for presepsin (0.99) was greater than for PCT+CRP (0.96), CRP (0.85) and PCT (0.91).

Rashwan et al. [20] Cross-sectional study CRP, hsCRP, Presepsin, PCT, IL-6 separately and in combination 168 neonates with clinical signs or symptoms of sepsis (66 with probable sepsis and 102 with proven sepsis, of which 47 were EONS and 55 LONS) Significantly higher serum levels of hsCRP and presepsin in EONS cases as compared to LONS; Significantly higher serum hsCRP, presepsin and PCT levels in proven vs probable sepsis group; Combination of hsCRP and PCT with either IL-6 or presepsin (especially in EONS) better predictor for neonatal sepsis.

Ganesan et al. [21] Prospective study IL-6, CRP and hsCRP Measured levels of biomarkers and compared with blood cultures 80 neonates (40 with clinically suspected sepsis and 40 healthy controls) Levels of all 3 biomarkers were significantly higher in clinically suspected sepsis group than in control group; hsCRP is less reliable biomarker on its own due to poor specificity; Risk of infection using hsCRP values:<0.5 mg/L (no risk), 0.5–1 mg/L (low risk), 1–3 mg/L (average risk) and > 3 mg/L (high risk); Combination of IL-6 and CRP are better predictors of neonatal sepsis

Wu et al. [22] Observational study SAA, PCT, hsCRP and a combination of the three Measured levels of biomarkers and compared differences in levels between those who responded to treatment and those who did not. 295 neonates (195 with sepsis and 100 healthy controls) Levels of all biomarkers were significantly higher in sepsis group prior to treatment; They were significantly lower in those who responded to treatment than those who did not respond; Sensitivity (92%) and specificity (75.38%) were found to be better when all three markers were combined together, as compared to individual levels

Shahkar et al. [24] Systematic Review and Meta-analysis IL-6 13 studies involving 1,044 neonates (353 with sepsis and 691 controls) Pooled sensitivity was 79%, pooled specificity was 84% and AUC was 0.89; Diagnostic accuracy of IL-6 was not affected by study quality, cut-off levels of IL-6 assay, birth-weight of neonates and control group status

Hedegaard et al. [1] Systematic Review IL-6 7 studies involving 852 neonates (312 with EOS, 423 with LOS and 117 controls) Variable sensitivity and specificity were observed, being high at 0 hour and lower after 24 and 48 hours; Positive and negative predictive values were highest at the onset of symptoms than after 24 hours

Smertka et al. [27] Observational study NGAL Measured serum and urinary NGAL levels on admission and on consecutive 3 days of treatment, and compared with PCT and CRP 102 neonates (51 with sepsis, 22 with severe sepsis and 29 uninfected controls) Strong correlation was found between serum and urinary NGAL and CRP and procalcitonin; Equally elevated levels of serum and urinary NGAL were seen in septic neonates with and without AKI; NGAL cannot be solely evaluated as a marker of AKI in septic newborns

Author	Type of study	Biomarker/Intervention (if any)	Study population	Result
Vouloumanou et al. [8]	Systematic Review and Meta-analysis	PCT	16 studies (1,959 neonates)	Pooled (95% CI) sensitivity and specificity were 81% (74–87) and 79% (69–87); Diagnostic accuracy was more for LONS (AUC: 0.95), than for EONS (AUC: 0.78)
Pontrelli et al. [6]	Systematic Review and Meta-analysis	PCT	17 studies (1,086 neonates and 322 children)	Sensitivity was 85%, (CI: 76–90%) and specificity was 54 (CI: 38–70%) at a cut-off of 2.0–2.5 ng/mL
Stocker et al. [9]	Randomised Controlled Intervention Trial	PCT PCT guided antibiotic therapy vs standard care antibiotic therapy	1710 neonates with sepsis (866 in PCT guided therapy group and 844 in standard therapy group)	Duration of therapy was significantly reduced in PCT-guided therapy group (51·8 vs 64·0 h); Length of hospital stay was also shorter in PCT-guided therapy group
Poggi et al. [14]	Prospective study	Presepsin Measured presepsin levels at days 0, 1, 3 and 5, along with CRP and PCT levels	40 preterm neonates ≤32 weeks gestation (19 with LOS and 21 non-infected controls)	Presepsin was higher in LOS group than control group; Presepsin showed borderline reduction on day 1 following therapy; Presepsin, PCT and CRP showed significant reduction on days 3 and 5
Mussap et al. [11]	Prospective study	Presepsin Measured presepsin levels at days 0 and 3	65 full term and preterm neonates (25 with bacterial sepsis, 15 with non-bacterial SIRS and 25 non-infected controls)	Significantly higher presepsin levels in bacterial sepsis than control; Significantly higher presepsin levels in non-bacterial SIRS group than control; No significant difference between levels in bacterial sepsis and non-bacterial SIRS; Recommended a presepsin cut-off of 600 ng/L for neonatal sepsis
Ozdemir et al. [13]	Prospective study	Presepsin Measured presepsin levels in neonates with EOS and healthy controls and compared effectiveness with PCT and CRP	69 term neonates (29 with EOS and 40 healthy controls)	Presepsin levels were significantly higher in EOS group at T0; Cut-off value for presepsin was 539 pg/mL with AUC of 0.772; Sensitivities of CRP, PCT, and presepsin at 0 hour were 83, 67, and 80%, whereas the specificities were 75, 67, and 75%, respectively
Degirmencioglu et al. [15]	Prospective study	Presepsin Measured levels of Presepsin, Fetuin A, CRP and IL-6 at days 0, 3 and 7 of diagnosis	55preterm neonates ≤32 weeks gestation (26 with culture proven LOS and 29 controls)	Presepsin was found to have 88.9% sensitivity, 88.9% specificity and AUC of 0.939 at cut-off of 823 ng/mL for culture-proven LOS
Ruan et al. [16]	Systematic Review and Meta-analysis	Presepsin, PCT, CRP and combination of PCT+CRP-	28 studies (2661 neonates)	Presepsin alone or a combination of PCT+CRP improve the accuracy of diagnosis of neonatal sepsis; AUC for presepsin (0.99) was greater than for PCT+CRP (0.96), CRP (0.85) and PCT (0.91).
Rashwan et al. [20]	Cross-sectional study	CRP, hsCRP, Presepsin, PCT, IL-6 separately and in combination	168 neonates with clinical signs or symptoms of sepsis (66 with probable sepsis and 102 with proven sepsis, of which 47 were EONS and 55 LONS)	Significantly higher serum levels of hsCRP and presepsin in EONS cases as compared to LONS; Significantly higher serum hsCRP, presepsin and PCT levels in proven vs probable sepsis group; Combination of hsCRP and PCT with either IL-6 or presepsin (especially in EONS) better predictor for neonatal sepsis.
Ganesan et al. [21]	Prospective study	IL-6, CRP and hsCRP Measured levels of biomarkers and compared with blood cultures	80 neonates (40 with clinically suspected sepsis and 40 healthy controls)	Levels of all 3 biomarkers were significantly higher in clinically suspected sepsis group than in control group; hsCRP is less reliable biomarker on its own due to poor specificity; Risk of infection using hsCRP values:<0.5 mg/L (no risk), 0.5–1 mg/L (low risk), 1–3 mg/L (average risk) and > 3 mg/L (high risk); Combination of IL-6 and CRP are better predictors of neonatal sepsis
Wu et al. [22]	Observational study	SAA, PCT, hsCRP and a combination of the three Measured levels of biomarkers and compared differences in levels between those who responded to treatment and those who did not.	295 neonates (195 with sepsis and 100 healthy controls)	Levels of all biomarkers were significantly higher in sepsis group prior to treatment; They were significantly lower in those who responded to treatment than those who did not respond; Sensitivity (92%) and specificity (75.38%) were found to be better when all three markers were combined together, as compared to individual levels
Shahkar et al. [24]	Systematic Review and Meta-analysis	IL-6	13 studies involving 1,044 neonates (353 with sepsis and 691 controls)	Pooled sensitivity was 79%, pooled specificity was 84% and AUC was 0.89; Diagnostic accuracy of IL-6 was not affected by study quality, cut-off levels of IL-6 assay, birth-weight of neonates and control group status
Hedegaard et al. [1]	Systematic Review	IL-6	7 studies involving 852 neonates (312 with EOS, 423 with LOS and 117 controls)	Variable sensitivity and specificity were observed, being high at 0 hour and lower after 24 and 48 hours; Positive and negative predictive values were highest at the onset of symptoms than after 24 hours
Smertka et al. [27]	Observational study	NGAL Measured serum and urinary NGAL levels on admission and on consecutive 3 days of treatment, and compared with PCT and CRP	102 neonates (51 with sepsis, 22 with severe sepsis and 29 uninfected controls)	Strong correlation was found between serum and urinary NGAL and CRP and procalcitonin; Equally elevated levels of serum and urinary NGAL were seen in septic neonates with and without AKI; NGAL cannot be solely evaluated as a marker of AKI in septic newborns

2 Future directions

Despite the availability of a plethora of studies showing a promising role of point of care biomarkers in neonatal sepsis, careful interpretation of these markers is required as these are mostly stress markers and can be elevated in many other conditions. Mahendiran et al. observed that PCT levels were raised in neonates with meconium aspiration syndrome, irrespective of the presence of infection. The difference in both groups was not significant. However, these levels were measured early in the course of the disease and not sequentially [29]. Specific cut-offs need to be defined for diagnosis of sepsis, ruling out other confounders. Combination of biomarkers has shown to increase the diagnostic performance as compared to individual ones. Zhang et al. showed that the predictive ability significantly improved when PCT, N-terminal brain natriuretic propeptide, Interleukin-6, Prothrombin time, Thrombin time, and Sequential Organ Failure Assessment (SOFA) score were combined for diagnosis sepsis in adults [30]. However, the cost involved remains a major hindering factor in translating research into clinical practice.

Box 1.

Key messages

POC testing methods are available for PCT, presepsin, hsCRP, IL-6, and NGAL which are faster and efficacious and hence are of great utility in time sensitive condition like neonatal sepsis.

Various systemic reviews and meta-analyses have been conducted to assess the efficacy of PCT, presepsin and IL-6 in diagnosis and monitoring of neonatal sepsis. However, more studies are required to determine the use of hsCRP and NGAL in the same.

Biomarkers, when used in combination with each other, or with clinical scores, can prove advantageous over the gold standard by eliminating the waiting time for blood culture results.

Biomarkers can be used to guide antibiotic therapy as it has been shown to reduce duration of treatment as well as duration of hospital stay.

Several stress conditions can lead to rise in the levels of the biomarkers. Therefore, specific cut-offs need to be established to rule out the confounders.

Combining biomarkers with clinical scores provide a practical approach where diagnostic accuracy can be increased without much increase in the cost involved. Scores, such as the PELOD-2 score and SOFA score, based on clinical and laboratory variables are being increasingly used for diagnosis and monitoring of sepsis and multiple organ dysfunction in the adult as well as neonatal population [31]. Kupperman et al. derived and validated a clinical prediction rule to identify febrile infants 60 days and younger at low risk for Serious Bacterial Infections using only urinalysis, absolute neutrophil count, and serum procalcitonin levels [32]. The development of such prediction rules may help in early and improved diagnostic ability in neonatal sepsis as well. Validation studies over a wider population should be carried out to establish the efficacy of such rules.

Footnotes

Acknowledgments

None.

Disclosures

The authors have no financial or ethical conflict of interest to declare.

Funding sources

None.

References

Hedegaard

, Wisborg

, Hvas

. Diagnostic utility of biomarkers for neonatal sepsis - a systematic review. Infect Dis (Auckl). 2015;47(3):117–24.

Delhi

. National Neonatal-Perinatal Database. NNPD Nodal Cent Dep Pediatr WHO Collab Cent Newborn Train Res All India Inst Med Sci [Internet]. 2005;1-70. Available from: https://www.newbornwhocc.org/pdf/nnpd_report_2002-03.PDF.

Wynn

. Defining neonatal sepsis. Curr Opin Pediatr. 2016;28(2):135–40.

Kellogg

, Ferrentino

, Goodstein

, Liss

, Shapiro

, Bankert

. Frequency of low level bacteremia in infants from birth to two months of age. Pediatr Infect Dis J. 1997;16(4):381–5.

Rooney

, Schilling

. Point-of-care testing in the overcrowded emergency department - Can it make a difference? Crit Care. 2014;18(1):1–7.

Pontrelli

, De Crescenzo

, Buzzetti

, Jenkner

, Balduzzi

, Calò Carducci

, et al. Accuracy of serum procalcitonin for the diagnosis of sepsis in neonates and children with systemic inflammatory syndrome: A meta-analysis. BMC Infect Dis. 2017;17(1):1–12.

Hendricks-Munoz

, Xu

, Mally

. Biomarkers for neonatal sepsis: Recent developments. Res Reports Neonatol. 2014;157.

Vouloumanou

, Plessa

, Karageorgopoulos

, Mantadakis

, Falagas

. Serum procalcitonin as a diagnostic marker for neonatal sepsis: A systematic review and meta-analysis. Intensive Care Med. 2011;37(5):747–62.

Stocker

, van Herk

, el Helou

, Dutta

, Fontana

, Schuerman

FABA

, et al. Procalcitonin-guided decision making for duration of antibiotic therapy in neonates with suspected early-onset sepsis: A multicentre, randomised controlled trial (NeoPIns). Lancet. 2017;390(10097):871–81.

10.

Kutz

, Hausfater

, Oppert

, Alan

, Grolimund

, Gast

, et al. Comparison between B·R·A·H·M·S PCT direct, a new sensitive point-of-care testing device for rapid quantification of procalcitonin in emergency department patients and established reference methods - A prospective multinational trial. Clin Chem Lab Med. 2016;54(4):577–84.

11.

Mussap

, Puxeddu

, Puddu

, Ottonello

, Coghe

, Comite

, et al. Soluble CD14 subtype (sCD14-ST) presepsin in premature and full term critically ill newborns with sepsis and SIRS. Clin Chim Acta [Internet]. 2015;451:65–70. Available from: https://dx-doi-org-s.web.bisu.edu.cn/10.1016/j.cca.2015.07.025.

12.

Lippi

, Cervellin

. Can presepsin be used for screening invasive fungal infections? Ann Transl Med. 2019;7(5):87–87.

13.

Ozdemir

, Elgormus

. Diagnostic value of presepsin in detection of early-onset neonatal sepsis. Am J Perinatol. 2017;34(6):550–6.

14.

Poggi

, Bianconi

, Gozzini

, Generoso

, Dani

. Presepsin for the detection of late-onset sepsis in preterm newborns. Pediatrics. 2015;135(1):68–75.

15.

Değirmencioğlu

, Ozer Bekmez

, Derme

, Öncel

, Canpolat

, Tayman

. Presepsin and fetuin-A dyad for the diagnosis of proven sepsis in preterm neonates. BMC Infect Dis. 2019;19(1):1–7.

16.

Ruan

, Chen

, Liu

, Zhao

, Xu

, Li

, et al. The combination of procalcitonin and C-reactive protein or presepsin alone improves the accuracy of diagnosis of neonatal sepsis: A meta-analysis and systematic review. Crit Care. 2018;22(1):1–9.

17.

Okamura

, Yokoi

. Development of a point-of-care assay system for measurement of presepsin (sCD14-ST). Clin Chim Acta [Internet]. 2011;412(23-24):2157–61.

18.

Sang

, Jung

, Sang

, Heuk

, Jae

, Ki

, et al. Evaluation of fluorescence hs-CRP immunoassay for point-of-care testing. Clin Chim Acta. 2005;356(1-2):172–7.

19.

Sharma

, Farahbakhsh

, Shastri

, Sharma

. Biomarkers for diagnosis of neonatal sepsis: a literature review. J Matern Neonatal Med. 2018;31(12):1646–59.

20.

Rashwan

, Hassan

, Mohey El-Deen

, Ahmed

AEA

. Validity of biomarkers in screening for neonatal sepsis - A single center -hospital based study. Pediatr Neonatol [Internet]. 2019;60(2):149–55.

21.

Ganesan

, Shanmugam

, Sattar

SBA

, Shankar

. Evaluation of IL-6, CRP and hs-CRP as early markers of neonatal sepsis. J Clin Diagnostic Res. 2016;10(5):13–7.

22.

, Hou

, Sun

, Cui

. The predictive value of joint detection of serum amyloid protein A, PCT, and Hs-CRP in the diagnosis and efficacy of neonatal septicemia. Eur Rev Med Pharmacol Sci. 2019;23(13):5904–11.

23.

Huang

, Ying

, Jiang

, Liu

, Tian

, Du

, et al. Rapid and sensitive detection of interleukin-6 in serum via time-resolved lateral flow immunoassay. Anal Biochem [Internet]. 2020;588:113468. Available from: https://doi.org/10.1016/j.ab.2019.113468.

24.

Shahkar

, Keshtkar

, Mirfazeli

, Ahani

, Roshandel

. The role of IL-6 for predicting neonatal sepsis: A systematic review and meta-analysis. Iran J Pediatr. 2011;21(4):411–7.

25.

Fischer

, Williams

, Wang

, Capio

, Briman

. Development of an IL-6 point-of-care assay: Utility for real-time monitoring and management of cytokine release syndrome and sepsis. Bioanalysis. 2019;11(19):1777–85.

26.

Cowland

, Borregaard

. Molecular characterization and pattern of tissue expression of the gene for neutrophil gelatinase-associated lipocalin from humans. Genomics. 1997;45(1):17–23.

27.

Smertka

, Wroblewska

, Suchojad

, Majcherczyk

, Jadamus-Niebroj

, Owsianka-Podlesny

, et al. Serum and urinary NGAL in septic newborns. Biomed Res Int. 2014;2014(interleukin 18).

28.

Lei

, Zhu

, Xia

, Feng

, Zhang

, Han

. A rapid and user-friendly assay to detect the Neutrophil gelatinase-associated lipocalin (NGAL) using up-converting nanoparticles. Talanta [Internet]. 2017;162:339–44.

29.

Mahendiran

, Batra

, Faridi

MMA

, Singh

. Procalcitonin as predictor of bacterial infection in meconium aspiration syndrome. Am J Perinatol. 2018;35(8):769–73.

30.

Zhang

, Khalid

, Jiang

. Diagnostic and predictive performance of biomarkers in patients with sepsis in an intensive care unit. J Int Med Res. 2019;47(1):44–58.

31.

Endo

, Suzuki

, Takahashi

, Shozushima

, Ishikura

, Murai

, et al. Presepsin as a powerful monitoring tool for the prognosis and treatment of sepsis: A multicenter prospective study. J Infect Chemother [Internet]. 2014;20(1):30–4.

32.

Kuppermann

, Dayan

, Levine

, Vitale

, Tzimenatos

, Tunik

, et al. A clinical prediction rule to identify febrile infants 60 days and younger at low risk for serious bacterial infections. JAMA Pediatr. 2019;173(4):342–51.