Acute phase reactant change in ankylosing spondylitis patients

Objective: To determine the high levels of acute phase reactants (APR) of ankylosing spondylitis (AS) patients at diagnosis and follow-up, to determine the characteristics of AS patients whose APS never increase during follow up, and to investigate the relationship between patients' high levels of APS and patients' clinical and genetic characteristics, activity levels and drugs used. Methods: 948 patients who were diagnosed with AS according to the modified 1984 New York criteria and followed-up at the Dokuz Eylül University Faculty of Medicine 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. Conclusion: High levels of acute phase reactants is not rare in AS patients. During follow-up CRP specifically will be positive in over 80% of patients. For AS, ESR and CRP should be considered the most significant laboratory diagnostics in clinical practice, as well as measuring patient activity levels. Keywords: Ankylosing spondylitis, acute phase reactant, erythrocyte sedimentation rate, C-reactive protein, disease activity index.