Serum osteocalcin levels in patients with psoriatic arthritis: an extended report

The aim of the study was to investigate the rate of bone formation in patients with psoriatic arthritis (PsA) compared to controls and patients with psoriasis vulgaris without PsA (PS). Osteocalcin (OC) and other parameters of bone turnover were measured in 32 patients with PsA and 17 patients with PS and compared to controls (n= 50). Patients with PsA do not generally present with different OC levels (3.0 ± 1.6 ng/ml), than controls (3.6 ± 1.17 ng/ml), if disease activity or sex are not considered. Women with PsA had significantly lower OC levels (2.28 ± 0.44 ng/ml) than female controls (4.11 ± 1.7 ng/ml) or women with PS (3.0 ± 0.89 ng/ml). However, mean disease activity (2.27 ± 1.0 vs 2.95 ± 0.92) was also significantly lower in women than men. Furthermore, we found a significant correlation between alkaline phosphatase (AP) and OC in all patients with PsA (r=0.49, P < 0.05). Disease activity of PsA had an influence on OC levels. Patients with no disease activity had lower OC levels (2.2 ± 0.7 ng/ml) than patients with a high activity (OC 3.92 ± 1.25, P < 0.05). Similar results were obtained with alkaline phosphatase. In addition, we found a significant correlation between clinical activity and OC (r= 0.38, P < 0.02) and alkaline phosphatase (r=0.49, P < 0.01). Patients with PsA show a corresponding increase in OC levels, if disease activity is high. The proliferative changes in active PsA may be related to inflammatory mechanisms coupled with bone formation. Received: 28 May 1999 / Accepted: 11 February 2000