Evaluation of Acute Phase Reactants in Patients with Ankylosing Spondylitis

Objective: To determine the high levels of acute phase reactants (APR) of ankylosing spondylitis (AS) patients at diagnosis and follow-up, and to investigate the relationship between patients’ high levels of APR and patients’ disease activity levels and clinical characteristics. Material and Methods : 948 patients who were diagnosed with AS according to the modified 1984 New York criteria and followed-up at the university rheumatology clinic were included in this study. The patients’ erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels across all visits were retrospectively reviewed through the registry and the hospital’s database. Results: At first visit, high levels of CRP and ESR were observed in 626 (68.5%) and 578 (64.6%) patients respectively. During follow-up 84.6% of patients had high CRP and 69.5% patients had high ESR, however in 10% of patients APRs did not increase at all. There was good correlation between ESR and CRP (r=0.666, p=0.000). A better correlation was observed at first visit between CRP and BASDAI (r=0.81, p=0.23) or ASDAS (r=0.468, p=0.000) compared to ESR and BASDAI (r=0.111, p=0.02) or ASDAS (r=0.334, p=0.000). Compared to BASDAI, ASDAS with either ESR (p=0.00) or CRP (very high disease activity-p=0.000, inactive disease-p=0.001) had better performance in evaluating the activity of the patient in inactive and very high levels of severe disease. Conclusions: Our results showed, high levels of acute phase reactants is not rare in AS patients. APR should be considered the most significant laboratory diagnostics in the evaluation of AS and/or response to the treatment.