Clinical significance of anti-mutated citrullinated vimentin antibodies in rheumatoid arthritis patients

Abstract

BACKGROUND:

Anti-mutated citrullinated vimentin (MCV) antibodies have recently been recommended as a better arthritis diagnostic marker.

OBJECTIVES:

To investigate the association between anti-MCV antibodies and the clinical, functional, and radiographic characteristics of rheumatoid arthritis (RA) patients.

METHODS:

This case-control study was conducted on 40 RA patients and 40 healthy subjects. All patients were subjected to an assessment of disease using the 28-joint DAS (DAS28) and Clinical Disease Activity Index (CDAI), function by HAQ-DI, physical activity by International Physical Activity Questionnaire (IPAQ), fatigue by Functional Assessment of Chronic Illness Therapy (FACIT), serological tests as well as anti-MCV Abs measurement. A plain X-ray of both hands and wrists was done.

RESULTS:

The anti-MCV Abs level was significantly higher in RA patients than in healthy controls ( $P<$ 0.001). The anti-MCV Abs had a significant positive correlation with DAS, CDAI, HAQ, RF, Anti-CCP, and CRP ( $P=$ 0.006, 0.013, 0.005, $<$ 0.001, $<$ 0.001and 0.041 respectively) and a significant negative correlation with FACIT ( $p=$ 0.007). Positive anti-MCV RA patients had significantly higher erosions, JSN, and a total sharp score.

CONCLUSIONS:

Anti-MCV Abs may contribute to poor physical activity and more fatigue in RA patients beyond their established role in disease activity and erosion.

Keywords

Arthritis anti-citrullinated protein antibodies fatigue rheumatoid serologic tests X-Rays

1. Background

A persistent autoimmune disease, rheumatoid arthritis (RA) involves multiple pathophysiological pathways that complicate the disease’s etiology and symptoms. Patient heterogeneity is important throughout the entire course of the illness. Untreated RA results in joint function loss and disability [1]. The justification for starting therapy earlier is that it enables biological processes to be modulated while they are more malleable and reversible. This phase has also been called a therapeutic window of opportunity [2]. Furthermore, the disease process may begin before symptoms manifest due to the formation of characteristic autoantibodies before disease presentation [3, 4].

As a result of the lack of physical signs and limited clinical symptoms, early diagnosis of RA is difficult. Rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPAs), which were included in the American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) new 2010 classification criteria for RA, helped in the earlier identification of RA patients [5].

The most popular commercial assay for detecting ACPAs is the anti-cyclic citrullinated peptide (anti-CCP) test, which employs synthetic cyclic citrullinated peptides that mimic RA epitopes. The first anti-CCP1 test was a cyclic derivative of a citrullinated fillagrin peptide. Anti-CCP2 and anti-CCP3 assays with more citrullinated epitopes were developed in the second and third generations to boost sensitivity. Anti-CCP antibodies showed greater specificity ( $>$ 95%) compared to RF for RA, but similar sensitivity [6].

Vimentin, histone, enolase, fibrinogen, fibronectin, fillagrin, and collagen type II are among the citrullinated proteins that ACPAs target [7]. Vimentin is an intermediate filament expressed by mesenchymal cells and serves as the main antigen for anti-Sa antibodies to bind to [8]. It was later found that vimentin’s glycine-to-arginine conversion boosts antibody reactivity. The enzyme-linked immunosorbent assay (ELISA), which was used to find IgG anti-mutated citrullinated vimentin (anti-MCV) autoantibodies, was then performed using the mutant and in vitro citrullinated recombinant human vimentin antigen [9].

Studies to better understand the clinical role of anti-MCV in RA patients are becoming increasingly important. Anti-MCV antibodies have recently been recommended as a better early arthritis diagnostic marker [10]. Several studies [11, 12] found that anti-MCV antibodies have the same specificity as anti-CCP antibodies but are more sensitive. Furthermore, a correlation has been found between anti-MCV antibody titers and both the severity of RA and the disease activity score (DAS) [12]. However, its relationship to RA patients’ functional impairment and fatigue has been researched in a few studies [13, 14]. Therefore, this research aimed to investigate the association between anti-MCV antibodies and several clinical and functional characteristics of RA patients as well as radiographic severity.

2. Methods

2.1 Study design and participants

This case–control study was conducted at the Department of Rheumatology, Rehabilitation, and Physical Medicine at Alexandria University Hospital. The study was conducted according to the ethical guidelines of the 1964 Declaration of Helsinki (2008 revision) and approved by the Ethics Committee of the Faculty of Medicine, Alexandria University, Egypt (approval number 00018699). Informed consent was obtained from all individual participants included in the study. The study included forty patients $>$ 16 years of age diagnosed as having RA based on the 2010 ACR/EULAR classification criteria [15]. Another 40 healthy persons of matched age, sex, and BMI were included as a control group. The smallest sample size was calculated using PASS 2020 software [16]. The exclusion criteria were patients with a history of other autoimmune diseases; other erosive joint diseases, such as erosive OA and gout; systemic diseases that affect bone quality, such as diabetes mellitus and renal diseases; infections, and malignancy.

2.2 Clinical assessment

All subjects completed a full medical history and thorough clinical examination. In the RA patient group, the activity of RA was assessed by the 28-joint DAS with CRP (DAS28-CRP) [17] and Clinical Disease Activity Index (CDAI) [18]. The degree of functional impairment in RA patients was assessed by the HAQ– Disability Index (HAQ-DI) [19]. The International Physical Activity Questionnaire (IPAQ) short form was used to assess the physical activity [20]. The Functional Assessment of Chronic Illness Therapy (FACIT) score was used to assess fatigue [21].

2.3 Radiological investigations

A plain X-ray of both hands and wrists in the postero-anterior view was done for all RA patients to detect bone erosions and juxta-articular osteopenia. Radiographic scoring of articular involvement was done using the Modified Sharp Score which includes 17 areas for erosions for each hand and wrist (5 proximal interphalangeal joints, 5 metacarpophalangeal joints, 1st metacarpal base, trapezium-trapezoid complex, lunate, triquetrum (and pisiform), radius and ulna). Erosions were scored from 1–5 points for each area with the highest score representing loss of more than 50% of either articular bone, yielding a total score of 0–170.

This scoring method additionally considers 18 regions for JSN for each hand and wrist, including the radiocarpal and radioulnar joints, as well as the 5 proximal interphalangeal joints, 5 metacarpophalangeal joints, 3rd–5th carpometacarpal joints, trapezium–trapezoid–scaphoid, and lunate–triquetrum joints. One point is awarded for focal narrowing, two points for diffuse narrowing that is less than 50% of the original joint space, and three points for reductions that are greater than 50%. Four points are awarded for ankylosis. As a result, JSN’s overall score [22] runs from 0 to 144.

2.4 Blood sample collection

Four milliliters of whole blood were collected by venipuncture from the antecubital vein under a complete aseptic technique into BD Vacutainer^® red top blood collection tubes containing clot activator (Becton, Dickinson and Company, USA). Blood was left to clot at room temperature for 30 minutes followed by centrifugation at 1300 g for 10 minutes to separate serum.

2.5 Laboratory investigations

C-reactive protein (CRP) and RF were measured using the BN Prospec system (Siemens Healthineers, Germany). Anti-CCP was measured using a BIO-FLASH chemiluminescent analyzer (INOVA Diagnostics, USA).

2.6 Measurement of serum anti-MCV antibody level

According to the manufacturer’s instructions, serum anti-MCV was measured using a commercial ELISA kit (ORGENTEC Diagnostika GmbH, Germany). A standard curve was used to detect the anti-MCV level in an unknown sample.

3. Results

Table 1
Sociodemographic, clinical, and functional characteristics of the studied RA patients

Characteristics	Values
Duration of disease, years
Minimum–maximum Mean (S.D.) Median (IQR)	0.08–15.0 6.87 $\pm$ 4.21 6.0 (3.75–10.0)
SJC ( $n$ )
Minimum–maximum Mean (S.D.) Median (IQR)	0.0–21.0 4.13 $\pm$ 4.80 2.50 (1.0–6.50)
Tender joint count ( $n$ )
Minimum–maximum Mean (S.D.) Median (IQR)	0.0–28.0 9.68 $\pm$ 7.52 8.0 (4.0–12.50)
DAS28-CRP grade, $n$ (%)
Remission ( $<$ 2.6) Low disease activity (2.6–3.2) Moderate disease activity (3.2–5.1) High disease activity ( $>$ 5.1)	5 (12.5) 4 (10.0) 17 (42.5) 14 (35.0)
CDAI grade, $n$ (%)
Remission (0–2.8) Low disease activity (2.9–10) Moderate disease activity (10.1–22) High disease activity ( $>$ 22)	2 (5.0) 7 (17.5) 13 (32.5) 18 (45.0)
FACIT
Minimum–maximum Mean (S.D.) Median (IQR)	3.0–44.0 23.08 $\pm$ 9.78 21.50 (16.0–30.0)
HAQ-DI, $n$ (%)
Mild to Moderate Moderate to Severe Sever to Very severe	20 (50.0) 18 (45.0) 2 (5.0)
IPAI
Inactive Minimally active HEPA Active	24 (60.0) 16 (40.0) 0 (0.0)
Methotrexate, $n$ (%) Hydroquinone, $n$ (%) Leflunomide, $n$ (%) Sulfasalazine, $n$ (%) Biologics (Etanercept), $n$ (%) (Golimumab), $n$ (%) Current use of corticosteroids, $n$ (%) No corticosteroids intake Corticosteroids intake Minimum–maximum Mean (S.D.) Median (IQR)	28 (70.0) 32 (80.0) 16 (40.0) 10 (25.0) 3 (7.5) 4 (10.0) 21 (52.5) 19 (47.5) 150.0–1800.0 755.3 $\pm$ 505.2 600.0 (450.0–990.0)

IQR: Inter quartile range; SD: Standard deviation.

Table 2

Laboratory and radiological parameters of RA patients

Characteristics	Values
RF, $n$ (%)
Negative ( $<$ 15) Positive ( $\geqslant$ 15)	16 (40.0) 24 (60.0)
ACPA, $n$ (%)
Negative ( $<$ 20) Positive ( $\geqslant$ 20)	18 (45.0) 22 (55.0)
CRP
Minimum–maximum Mean (S.D.) Median (IQR)	0.52–40.0 9.07 $\pm$ 10.68 6.43 (1.87–11.95)
Sharp score
Erosions
Minimum–maximum Mean (S.D.) Median (IQR)	0.0–53.0 11.08 $\pm$ 12.50 8.0 (0.0–15.50)
JSN
Minimum–maximum Mean (S.D.) Median (IQR)	0.0–54.0 16.13 $\pm$ 15.98 12.0 (1.0–24.0)
Total
Minimum–maximum Mean (S.D.) Median (IQR)	0.0–107.0 27.20 $\pm$ 27.24 20.50 (2.50–40.0)

IQR: Inter quartile range; SD: Standard deviation.

The study included 38 (95%) females and 2 (5%) men aged between 24 to 54 years old with a mean of 40.13 years old with RA, their clinical, and functional disease criteria are listed in Table 1. The DAS28-CRP score showed that 14 patients (35%) had high disease activity, while the CDAI indicated that 18 patients (45%) had high disease activity. Corticosteroids were administered to 47.5% of the patients in total. In Table 2, laboratory, and radiographic results of the patients are shown. 24 patients (60%) had positive RF and 22 patients (55%) had positive anti-CCP. The total sharp score was 20.50 (2.50–40.0), with a range of 0.0–107.0.

Table 3

Comparison between two studied groups regarding gender, age, BMI and anti-MCV serum level

	Patients ( $n=$ 40)		Control ( $n=$ 40)		Test of sig.	$p$
	No.	%	No.	%
Gender
Female	38	95.0	38	95.0	$\chi^{2}=$ 0.000	^FEp= 1.000
Male	2	5.0	2	5.0
Age (/years)
Min.–Max.	24.0–54.0		22.0–54.0		$t=$ 0.342	0.733
Mean $\pm$ SD.	40.13 $\pm$ 7.19		40.75 $\pm$ 9.06
Median (IQR)	40.0 (34.5–45.0)		43.5 (33.0–48.0)
BMI
Min.–Max.	21.46–43.39		20.02–37.80		$t=$ 1.619	0.110
Mean $\pm$ SD.	30.20 $\pm$ 5.28		28.41 $\pm$ 4.59
Median (IQR)	29.37 (25.48–34.43)		29.04 (24.36–31.88)
Anti-MCV concentration
Min.–Max.	24.06–1176.5		7.96–109.8		$U=$ 127.0^*	$<$ 0.001^*
Mean $\pm$ SD.	521.7 $\pm$ 471.7		43.38 $\pm$ 26.33
Median (IQR)	272.8 (88.91–1101.4)		38.81 (22.23–60.69)

$t$ : Student $t$ -test; $\chi^{2}$ : Chi square test; FE: Fisher exact; U: Mann whitney test; $p$ : $p$ value for comparing between the two studied groups; ^*: Statistically significant at $p\leqslant$ 0.05.

Table 3 compares age, BMI, and anti-MCV levels between RA patients and healthy people. Age and BMI did not statistically differ between the two groups, however, there was a statistically significant difference between them as regards the serum level of anti-MCV ( $P<$ 0.001), which was higher in the patient group. The study of the ROC curve for anti-MCV as a predictor of RA is presented in Supplemental Table S1 and Fig. S1. The curve’s area under it was calculated to be 0.921, and a suggested cut-off value of $>$ 84.825 IU/ml was proposed with a sensitivity of 80% and a specificity of 95%.

Table 4

Correlation between anti-MCV concentration with different parameters in patients’ group ( $n=$ 40)

Anti-MCV concentration vs.	${r}_{s}$	$p$
Age (/years)	0.259	0.107
BMI (kg/m²)	$-$ 0.066	0.685
Weight (kg)	$-$ 0.029	0.860
Height (meters)	0.178	0.271
Duration of disease (/years)	0.321	0.043^*
Duration of morning stiffness (min.)	0.070	0.669
SJC	0.481	0.002^*
TJC	0.278	0.082
DAS28/CRP	0.423	0.006^*
CDAI	0.388	0.013^*
HAQ score	0.438	0.005^∗
FACIT	$-$ 0.417	0.007^*
RF	0.559	$<$ 0.001^*
Anti -CCP	0.712	$<$ 0.001^*
CRP	0.324	0.041^*
Erosions	0.238	0.140
JSN	0.211	0.190
Total	0.222	0.169

$r_{s}$ : Spearman coefficient; ^*: Statistically significant; at $p\leqslant$ 0.05. $U$ : Mann Whitney test.

Thirty-two (80%) RA patients had positive anti-MCV based on the cut-off value as detected by the ROC curve. The correlation between the serum anti-MCV level and the different clinical and serological features of our studied patients is presented in Table 4. There were significant positive correlations between the level of anti-MCV and disease duration, SJC, DAS, CDAI, HAQ, RF, Anti-CCP, and CRP ( $P=$ 0.043, 0.002, 0.006, 0.013, 0.005, $<$ 0.001, $<$ 0.001and 0.041 respectively) and a significant negative correlation with FACIT ( $p=$ 0.007).

There was a significant association between high anti-MCV serum levels with inactive IPAQ ( $p=$ 0.014). Moreover, there was no significant correlation between serum level of CRP and either RF or anti-CCP levels ( $p=$ 0.116 or 0.192 respectively), data not shown.

Table 5

Relation between anti-MCV with different parameters in patients ( $n=$ 40)

	Anti -MCV				Test of sig.	$p$
	Negative ( $\leqslant$ 84.825) ( $n=$ 8)		Positive ( $>$ 84.825) ( $n=$ 32)
Duration of disease (/years)
Mean $\pm$ SD.	4.29	$\pm$ 3.18	7.52	$\pm$ 4.23	$t=$ 2.012	0.051
Median (Min.–Max.)	4.50	(0.33–10.0)	7.50	(0.08–15.0)
SJC
Mean $\pm$ SD.	0.88	$\pm$ 0.99	4.94	$\pm$ 5.03	$U=$ 38.0^*	0.001^*
Median (Min.–Max.)	1.0	(0.0–3.0)	3.0	(0.0–21.0)
TJC
Mean $\pm$ SD.	4.88	$\pm$ 3.52	10.88	$\pm$ 7.80	$U=$ 70.0	0.051
Median (Min.–Max.)	5.50	(0.0–10.0)	10.0	(0.0–28.0)
DAS28/CRP
Mean $\pm$ SD.	3.19	$\pm$ 1.09	4.75	$\pm$ 1.34	$t=$ 3.050^*	0.004^*
Median (Min.–Max.)	3.40	(1.51–4.66)	4.89	(2.45–6.98)
CDAI
Mean $\pm$ SD.	11.75	$\pm$ 8.33	26.63	$\pm$ 15.66	$t=$ 3.680^*	0.001^*
Median (Min.–Max.)	12.50	(0.0–24.0)	26.50	(3.0–62.0)
HAQ score
Mean $\pm$ SD.	0.78	$\pm$ 0.41	1.29	$\pm$ 0.50	$t=$ 2.681^*	0.011^*
Median (Min.–Max.)	0.88	(0.13–1.25)	1.19	(0.50–2.25)
IPAQ
Inactive	2	(25.0%)	22	(68.8%)	$\chi^{2}=$ 5.104^*	^FEp= 0.042^*
Minimally active	6	(75.0%)	10	(31.3%)
FACIT
Mean $\pm$ SD.	30.88	$\pm$ 9.16	21.13	$\pm$ 9.05	$t=$ 2.720^*	0.010^*
Median (Min.–Max.)	30.50	(19.0–44.0)	20.0	(3.0–38.0)
RF
Mean $\pm$ SD.	80.36	$\pm$ 98.47	196.6	$\pm$ 293.8	$U=$ 100.0	0.359
Median (Min.–Max.)	11.55	(10.50–233.0)	62.50	(10.50–1170.0)
Anti -CCP
Mean $\pm$ SD.	61.56	$\pm$ 146.51	556.0	$\pm$ 885.7	$U=$ 60.500^*	0.020^*
Median (Min.–Max.)	6.70	(4.60–423.30)	59.85	(4.60–2776.70)
CRP
Mean $\pm$ SD.	3.64	$\pm$ 3.69	10.43	$\pm$ 11.45	$U=$ 70.500	0.051
Median (Min.–Max.)	2.52	(0.52–10.70)	6.72	(0.82–40.0)
Erosions
Mean $\pm$ SD.	2.75	$\pm$ 4.23	13.16	$\pm$ 13.05	$U=$ 52.500^*	0.009^*
Median (Min.–Max.)	0.0	(0.0–11.0)	11.0	(0.0–53.0)
JSN
Mean $\pm$ SD.	6.0	$\pm$ 6.52	18.66	$\pm$ 16.69	$U=$ 67.0^*	0.039^*
Median (Min.–Max.)	4.50	(0.0–16.0)	19.0	(0.0–54.0)
Total
Mean $\pm$ SD.	8.75	$\pm$ 9.91	31.81	$\pm$ 28.31	$U=$ 59.500^*	0.018^*
Median (Min.–Max.)	6.50	(0.0–27.0)	29.0	(0.0–107.0)

SD: Standard deviation; $t$ : Student $t$ -test; $U$ : Mann whitney test; $\chi^{2}$ : Chi square test; FE: Fisher exact. $p$ : $p$ value for Relation between Anti MCV with different parameters; ^*: Statistically significant at $p\leqslant$ 0.05.

The relation between the serum anti-MCV level and different clinical, serological, and radiological parameters in RA patients is presented in Table 5. Patients with positive Anti MCV Abs had significantly higher SJC, DAS-28, CDAI, and HAQ-DI with $p=$ 0.001, 0.004, 0.001, and 0.011 respectively, and a significantly lower FACIT score with $p=$ 0.010. Patients with positive anti-MCV were inactive based on IPAQ compared to those with negative anti-MCV (FEp $=$ 0.042). Positive anti-MCV RA patients had significantly higher anti-CCP, erosions, JSN, and total sharp scores with $p=$ 0.020, 0.009, 0.039, and 0.018 respectively.

Table 6

Comparison between four studied subgroups of positivity of (RF, anti-CCP and anti-MCV) ( $n=$ 40)

	Negative ( $n=$ 5)		$+$ ( $n=$ 9)		$++$ ( $n=$ 9)		$+++$ ( $n=$ 17)		Test of sig.	$p$
Duration of disease (/years)
Mean $\pm$ SD.	4.40	$\pm$ 2.07	6.56	$\pm$ 4.11	6.76	$\pm$ 5.29	7.82	$\pm$ 4.10	$F=$ 0.873	0.464
Median (Min.–Max.)	5.0	(1.0–6.0)	6.0	(0.08–13.0)	5.0	(0.33–15.0)	8.0	(1.0–15.0)
SJC
Mean $\pm$ SD.	0.80	$\pm$ 1.30	5.22	$\pm$ 6.28	2.67	$\pm$ 2.55	5.29	$\pm$ 5.10	$H=$ 7.940^*	0.047^*
Median (Min.–Max.)	0.0	(0.0–3.0)	3.0	(1.0–21.0)	1.0	(1.0–7.0)	5.0	(0.0–20.0)
TJC
Mean $\pm$ SD.	5.0	$\pm$ 3.61	9.56	$\pm$ 7.20	9.11	$\pm$ 9.58	11.41	$\pm$ 7.24	$H=$ 3.664	0.300
Median (Min.–Max.)	5.0	(0.0–10.0)	8.0	(3.0–24.0)	6.0	(0.0–28.0)	12.0	(1.0–22.0)
DAS28/CRP
Mean $\pm$ SD.	3.16	$\pm$ 1.14	4.56	$\pm$ 1.11	4.05	$\pm$ 1.64	4.95	$\pm$ 1.35	$F=$ 2.567	0.070
Median (Min.–Max.)	3.25	(1.51–4.66)	4.18	(3.13–6.98)	4.06	(1.80–6.66)	5.38	(2.53–6.97)
CDAI
Mean $\pm$ SD.	11.80	$\pm$ 8.61	25.0	$\pm$ 16.10	19.44	$\pm$ 17.21	28.65	$\pm$ 14.71	$F=$ 1.905	0.146
Median (Min.–Max.)	11.0	(0.0–24.0)	20.0	(10.0–62.0)	14.0	(1.0–48.0)	31.0	(5.0–54.0)
HAQ score
Mean $\pm$ SD.	0.78	$\pm$ 0.41	1.14	$\pm$ 0.33	1.03	$\pm$ 0.65	1.43	$\pm$ 0.47	$F=$ 2.924	0.047^*
Median (Min.–Max.)	0.88	(0.13–1.25)	1.0	(0.75–1.88)	0.88	(0.25–2.25)	1.50	(0.63–2.25)
IPAQ
Inactive	1	(20.0%)	6	(66.7%)	4	(44.4%)	13	(76.5%)	$\chi^{2}=$ 6.045	^MCp= 0.100
Minimally active	4	(80.0%)	3	(33.3%)	5	(55.6%)	4	(23.5%)
FACIT
Mean $\pm$ SD.	31.20	$\pm$ 8.96	22.56	$\pm$ 7.78	26.22	$\pm$ 12.42	19.29	$\pm$ 8.02	$F=$ 2.600	0.067
Median (Min.–Max.)	31.0	(9.0–44.0)	24.0	(6.0–33.0)	30.0	(3.0–42.0)	16.0	(8.0–35.0)
CRP
Mean $\pm$ SD.	2.84	$\pm$ 2.85	6.29	$\pm$ 4.26	11.35	$\pm$ 12.85	11.16	$\pm$ 12.67	$H=$ 3.881	0.275
Median (Min.–Max.)	1.48	(0.82–7.52)	6.47	(0.52–13.20)	7.0	(0.82–39.90)	6.62	(1.01–40.0)
Erosions
Mean $\pm$ SD.	3.0	$\pm$ 4.80	8.56	$\pm$ 9.11	11.33	$\pm$ 8.56	14.65	$\pm$ 16.11	$H=$ 4.438	0.218
Median (Min.–Max.)	0.0	(0.0–11.0)	7.0	(0.0–27.0)	11.0	(0.0–23.0)	12.0	(0.0–53.0)
JSN
Mean $\pm$ SD.	8.80	$\pm$ 6.76	10.78	$\pm$ 13.15	17.78	$\pm$ 16.55	20.24	$\pm$ 18.31	$H=$ 2.526	0.471
Median (Min.–Max.)	8.0	(0.0–16.0)	4.0	(0.0–30.0)	19.0	(0.0–47.0)	19.0	(0.0–54.0)
Total
Mean $\pm$ SD.	11.80	$\pm$ 10.99	19.33	$\pm$ 19.67	29.11	$\pm$ 24.71	34.88	$\pm$ 33.25	$H=$ 3.069	0.381
Median (Min.–Max.)	8.0	(0.0–27.0)	18.0	(0.0–57.0)	28.0	(0.0–70.0)	30.0	(0.0–107.0)

SD: Standard deviation; $F$ : $F$ for One way ANOVA test; $H$ : $H$ for Kruskal Wallis test; $\chi^{2}$ : Chi-square test; MC: Monte Carlo; $p$ : $p$ value for comparing between the four studied subgroups. ^*: Statistically significant at $p\leqslant$ 0.05.

A comparison between RA patients with negative serology, single, double, and triple antibody positivity is shown in Table 6. There were significant differences between the four groups regarding only SJC and HAQ, $p=$ 0.047 for both being higher in those with triple positivity. Two examples of our patients regarding radiographic assessment are shown as Supplementary Figs S2 and S3.

4. Discussion

Although clinical criteria must still be met, the presence of distinct autoantibodies in sera is essential for the diagnosis of RA and may also indicate prognosis [23]. This study investigated the connection between anti-MCV and RA disease characteristics, with an emphasis on fatigue and functional impairment. The percentage of anti-MCV-positive RA patients that we found to be 80% is considered a high level and is comparable to the numbers reported in earlier studies (80.95, 80%, 69.7%, 76.6%, 78.2%, and 77.5% [1, 13, 14, 24, 25, 26]).

Vimentin is an intermediate filament widely expressed by mesenchymal cells and macrophages. It is easily found in synovium. Apoptotic macrophages have changed proteins, and if the apoptotic material is not entirely removed, antibodies to citrullinated vimentin may develop [27]. The theory that vimentin may start the early immune response in RA [28] helps to explain this. By binding to the surface of antigen-presenting cells, HLA-DR4 stimulates T cells and may play a role in certain RA pathogenic pathways.

The current study found a strong positive association between the RA disease activity scores (DAS, CDAI, and SJC) and the serum anti-MCV level. Furthermore, patients with positive anti-MCV had significantly greater SJC, DAS-28, and CDAI compared to those with negative anti-MCV. These findings are consistent with those reported by Sirayildiz et al. (2013), Mohammed HS et al. 2023, and Zhu and Feng (2013) [29, 30, 13], who discovered a high association between anti-MCV titers and DAS-28, VAS, and ESR. Keskin et al. [31] reported similar results in a three-year follow-up research with 427 RA patients, showing that those with active RA had higher anti-MCV titers than those with inactive illness.

However, Ursum et al. found a weak correlation between anti-MCV antibodies and disease activity in early RA patients [32]. Furthermore, there were no appreciable differences in DAS28, ESR, RF, CRP, or disease duration between the anti-MCV positive and anti-MCV negative groups. This outcome was in line with other studies’ findings, which showed no statistically significant relationship between anti-MCV levels and the DAS28 and ESR [13, 33].

These variations in outcomes could be the consequence of selecting RA patients at different stages. The amount of pro-inflammatory cytokines, auto-antibodies, and tissue-damaging substances varies between patients with established and early stages of RA [34]. Furthermore, differences in treatment approaches and patient reactions to treatment may be the cause of these differences [35].

The results of the current study showed that CRP had a substantial positive correlation with anti-MCV but not with anti-RF or anti-CCP. These findings are like those of Zahran WE, et al. [36], who discovered that although there was a significant correlation between anti-MCV antibodies and CRP and ESR, there was no significant correlation for RF IgA, RF-IgM, or anti-CCP antibodies. They recommended that serum anti-MCV autoantibodies be measured in conjunction with ESR and CRP as a straightforward laboratory regimen for tracking RA patients’ disease activity. The stronger association between disease activity and serum CRP than between autoimmunity activity may be explained by these findings [37].

Elevated anti-MCV Abs worsened patients’ impairment and negatively affected physical activity, as demonstrated by the current study, which found a substantial positive link with HAQ score and a significant association with inactive IPAQ. Our results are consistent with those of El Shazly et al., who investigated the impact of anti-MCV on disability [13]. We also found a significant difference in IPAQ inactivity between RA patients who tested positive for anti-MCV and those who tested negative. This may be explained by the positive correlation found between the degree of damage shown by hand bone erosion (HAQ) and the degree of inflammation shown by DAS28, as well as the impact of anti-MCV Abs on the functional performance of the patients under study.

The literature has no information regarding how this autoantibody influences fatigue. Among the related findings of our study is the significant negative correlation between anti-MCV and FACIT scores. Recent work from the OMERACT conference [38] has brought fatigue to light as a significant patient outcome, which has contributed to its increased focus. It has been proposed that disease-specific mechanisms, such as inflammation and joint damage, are the cause of fatigue [38]. Pro-inflammatory cytokines, which are essential to the development of the disease, are most likely the inflammatory processes that cause RA’s early fatigue [39]. By finding the anti-MCV as a potential tiredness predictor, our findings may aid in the diagnosis and treatment of fatigue.

In this study, there were statistically significant positive correlations between the level of anti-MCV and either anti-RF or anti-CCP. Furthermore, compared to RA patients with negative anti-MCV, those with positive anti-MCV levels had significantly higher levels of anti-CCP. The same robust associations were observed between anti-MCV and anti-CCP antibodies, according to a study by Khalifa et al. [4]. According to Engelmann et al. [41], cross-reactivity investigations between anti-MCV and anti-CCP antibodies reveal that both antibodies target some shared epitopes, which may explain the high positive relationship between these antibodies. Numerous studies by Mutlu et al. [42] and El Shazly et al. [13] found the same outcome. In the current study, there was a substantial association between anti-MCV and anti-CCP, but a low correlation between RF.

In the current study, we found that patients with positive anti-MCV RA had significantly higher JSN, total sharp score on the Modified Sharp score, and erosions. Our results are in line with those of Syversen et al. [43], who found that anti-MCV antibodies were strong predictors of radiographic progression in individuals with RA. Anti-MCV-positive patients had faster rates of radiographic destruction than anti-MCV-negative patients between baseline and two years, especially between one year and two years, even though both groups’ radiographic scores at the time points under study were similar, according to Mathsson and colleagues [29]. This finding emphasizes the importance of anti-MCV positivity in determining disease severity as determined by joint radiological damage.

Lastly, on comparing single, double, and triple antibody positivity in our RA patients as regards different disease characteristics, there were statistically significant differences between the three groups regarding SJC and HAQ, being higher in the triple positivity subgroup. This finding adds to the importance of aggressive management of RA patients with more antibody positivity as they usually have an aggressive course.

5. Conclusion

Our findings suggest that, in addition to their known effects on disease activity and erosion, anti-MCV may also contribute to inadequate physical activity and increased fatigue in RA patients. The list of traits that should be considered more in the treatment of patients who are anti-MCV positive grows with the report of the link between weariness and insufficient physical activity. Furthermore, our data suggest that anti-MCV may serve as useful biomarkers of the severity of RA disease.

Author contributions

RE is the guarantor. AH, RB, DM, RT, and RE contributed to the experimental work. AH handled the statistical analysis of the data. All authors revised the paper critically for intellectual content and approved the final version. All authors agree to be accountable for the work and to ensure that any questions relating to the accuracy and integrity of the paper are investigated and properly resolved.

Declaration of conflict of interest

The authors declare no competing interests.

Funders

None.

Prior presentations

None.

Data availability

All data generated or analyzed during this study are included in this published article [and its supplementary information files].

Supplementary data

The supplementary files are available to download from http://dx.doi.org/10.3233/HAB-240007.

Footnotes

Acknowledgments

The authors would like to thank the patients in the rheumatology clinic for their willingness to enroll in this study.

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Clinical significance of anti-mutated citrullinated vimentin antibodies in rheumatoid arthritis patients

Abstract

BACKGROUND:

OBJECTIVES:

METHODS:

RESULTS:

CONCLUSIONS:

Keywords

1. Background

2. Methods

2.1 Study design and participants

2.2 Clinical assessment

2.3 Radiological investigations

2.4 Blood sample collection

2.5 Laboratory investigations

2.6 Measurement of serum anti-MCV antibody level

3. Results

Table 1 Sociodemographic, clinical, and functional characteristics of the studied RA patients

5. Conclusion

Author contributions

Declaration of conflict of interest

Funders

Prior presentations

Data availability

Supplementary data

Footnotes

Acknowledgments

References

Table 1
Sociodemographic, clinical, and functional characteristics of the studied RA patients