Bone mineral density and bone remodelling in Tunisian patients with ankylosing spondylitis: A cross-sectional study

Aim of the workTo assess the bone turnover markers and bone mineral density (BMD) in ankylosing spondylitis (AS) patients and to evaluate their association with clinical variables.Patients and methodsForty-seven AS patients were compared with 47 matched control. Clinical features and inflammatory parameters were assessed. C-terminal telopeptide fragments of type I collagen (CTX), alkaline phosphatases (ALP), N-terminal propeptide of type I procollagen (PINP) serum levels, and BMD of the lumbar spine and femoral neck were evaluated. The Bath AS disease activity and functional indices (BASDAI and BASFI) were assessed.ResultsMean serum levels of C-reactive protein, ALP and CTX were higher in AS patients than control (p = 0.001, p = 0.001 and p = 0.027 respectively). Osteopenia and osteoporosis were significantly more frequent in AS patients (57.4%) than control (21.3%) (p < 0.001). The PINP and ALP significantly correlated with disease duration (r = 0.33, p = 0.02 and r = 0.3, p = 0.04 respectively). BMD of the femoral neck was significantly lower in AS patients with history of coxitis than AS patients without (p = 0.02). Patients on anti-tumour necrosis factor (TNFα) therapy had higher T score (lumbar spine) compared to those not. Multivariate regression showed that CRP levels and disease activity were independently associated with low BMD and T score (lumbar) was significantly associated with anti-TNF use (p = 0.007).ConclusionsAn increase in bone turnover markers and decrease of BMD were observed in AS patients. Inflammatory activity of AS was associated to hyper bone remodelling and decrease of BMD. Anti-TNF use seems to be beneficial on AS inflammation and therefore on the BMD.