Serum soluble CD26 and CD30 levels in patients with rheumatoid arthritis and the assessment of their relationship with disease activity

The aim of this study was to compare serum soluble CD26 (sCD26) and soluble CD30 (sCD30) levels in patients with rheumatoid arthritis (RA) and healthy controls and to determine their clinical significance in patients with RA.Forty-eight patients (38 women, 10 men) with RA according to American Collage of Rheumatology criteria and at least one year follow up, enrolled in this study and compared with thirty healthy controls (22 women, 8 men). To evaluate disease activity, the disease activity score 28 (DAS28) was calculated. Physical function capacity (disability) was assessed with Turkish version of the health assessment questionnaire (HAQ). Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and rheumatoid factor levels were determined by routine laboratory methods. Serum sCD26 and sCD30 levels of the patients with RA and healthy controls were measured by ELISA. Radiographic assessment of hands joints was evaluated according to the modified Larsen score.There was no significant difference with respect to the age (p = 0.641) and gender (p = 0.552) between patients with RA and healthy controls. The mean disease duration was 5.5±4.5 (1-18) years and the mean DAS28 score was 4.03±1.48 (1.79-7.03) in patients with RA. Serum sCD26 levels were significantly lower (p = 0.011) and sCD30 levels were significantly higher (p = 0.008) in patients with RA compared to healthy controls. While the mean sCD26 level was not different between the high/moderate active and low active patient groups (p = 0.594), the mean sCD30 level was significantly higher in the high/moderate active group than the low active group (p = 0.018). There was no relationship between serum sCD26 levels and disease activity parameters, whereas sCD30 levels were positively correlated with clinical and laboratory parameters of disease activity including morning stiffness, pain, patient's and physcian's general health assessment, number of tender and swollen joints, DAS28, HAQ, ESR and CRP levels. There was no significant correlation between radiological scoring of joint damage and sCD26 or sCD30 levels (p = 0.574 and p = 0.869, recpectively). Lastly, serum sCD26 and sCD30 levels were not different between patients using only prednisolon and prednisolon plus methotrexate (p = 0.197 and p = 0.309, recpectively).This study shows that serum sCD30 levels are increased and correlated with disease activity in patients with RA. Thus, serum sCD30 levels may be a new parameter in following the disease activity. Although serum sCD26 is lowered in RA it seems to be unrelated to disease activity. Longitudinal studies including more participants is necessary to confirm these findings.Key words: Rheumatoid arthritis, CD26, CD30, disease activity