Evaluation of serum CGRP (calcitonin gene-related peptide) levels in diseases diagnosed with rheumatoid arthritis and its relationship with disease follow-up and disease activity

Aim: The aim of this study is to determine serum calcitonin gene-related peptide (CGRP) levels in rheumatoid arthritis (RA) patients compared to healthy controls, and to investigate the place of serum CGRP levels in RA in the follow-up of disease and its relationship with disease activity. Material and Method: A total of 120 people between the ages of 18-65 participated in the study; 40 healthy controls (30 females, 10 males; age 50.9±7.1 years) and 80 patients (60 females, 20 males; age 51.2±9.9 years) diagnosed with RA according to the ACR/EULAR 2010 RA Diagnostic Criteria were included. Patients who were positive for rheumatoid factor (RF) and/or anti-cyclic citrulized peptide antibody (anti-CCP) were grouped as seropositive and negative patients as seronegative. Of the RA patients, 40 were seronegative and 40 were seropositive. Demographic data and anthropometric measurements of the patient and control groups were recorded. Disease Activity Score 28 (DAS-28), health assessment questionnaire (HAQ), visual analog scale (VAS), erythrocyte sedimentation rate (ESH) and C-reactive protein (CRP) values were measured to determine disease activity in the patient group. Serum CGRP levels were studied by enzyme-linked immunosorbent assay method. Findings: The median serum CGRP level (91.1 pg/ml) measured in RA patients was statistically significantly higher than the control group (40.8 pg/ml) (p<0.001). Median serum CGRP level was significantly higher in seropositive patients (118.7 pg/ml) than seronegative patients (66.1 pg/ml) (p=0.017). The most appropriate cut-off value for the CGRP value separating the patient and control groups was 61.78 pg/ml with 70% sensitivity and 87.5% specificity as a result of ROC analysis (AUC: 0.839 p<0.001). Serum CGRP, CRP, ESH, HAQ, VAS-Patient, VAS-Physician values were found to be significantly higher in patients with active RA compared to RA patients in remission (p<0.001). CGRP, CRP, ESH values were found to be effective factors on DAS-28 activity (remission-active). It was determined that the increase in CGRP, CRP and ESR values increased the odds ratio of being active 1.012, 2.295 and 1.083 times, respectively, according to DAS-28 (p<0.05). A significant correlation was found between the CGRP values of the patients and the values of DAS-28, HAQ, VAS-Patient and VAS-Physician (p=0.001, p=0.006, p<0.001, p=0.001). No correlation was found between CGRP and CRP, ESR, disease duration, age, and morning stiffness. CGRP value was found to be significantly higher in RF positive patients than in negative patients (p=0.012). According to DAS-28, the most appropriate cut-off value for the CGRP value that separates the remission and active groups was 91.45 ng/ml with 65.3% sensitivity and 77.4% specificity as a result of ROC analysis (AUC: 0.750, p<0.001). Conclusion: The high CGRP in RA patients suggests that it may play a role in the pathogenesis of RA. The significant relationship between CGRP levels and seropositivity and disease activity increases the importance of CGRP in RA. CGRP may play a functional role in the diagnosis, follow-up and determination of the activity of RA. Keywords: Rheumatoid Arthritis, CGRP, Disease activity