Objective: Ankylosing spondilitis (AS) is a chronic inflammatory disease involving primarily the skeletal system, the peripheral joints and extra-articular structures. C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are commonly used assays for measuring acute phase response, but CRP and ESR are influenced by several factors unrelated to inflammation. Mean platelet volume (MPV) is a simple marker of subclinical inflammation. In this study, we aimed to investigate the correlation between MPV and clinical activity indices, namely Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) in patients with AS.

Materials and Methods: Thirty-seven AS patients (16 active, 21 inactive) were enrolled in the study. Disease activity was determined by Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) score in AS patients. ESR, CRP, MPV and other CBC parameters were evaluated. Age and gender- matched 25 healthy subjects were used as the control group.

Results: Neutrophil and platelet counts, and MPV, ESR, CRP values were significantly higher in patients with AS than the controls (p<0.05). Significantly higher platelet, ESR and CRP values were found in the active AS group (p<0.05). MPV was significantly lower in active group than inactive group (8.95±0.90 vs 10.11±0.90, respectively).

Conclusion: Our results suggest that MPV may be useful in the assessment of the disease activity and as a confirmatory test for CRP and ESR results in patients with AS.