Soluble receptor activator of nuclear factor-kB ligand (RANKL) and osteoprotegerin in ankylosing spondylitis: OPG is associated with poor physical mobility and reflects systemic inflammation

The objective of the study was to investigate the role of receptor activator of nuclear factor-kB ligand (RANKL) and osteoprotegerin (OPG) in ankylosing spondylitis (AS). Serum levels of soluble RANKL (sRANKL) and OPG were measured in 42 AS patients and 26 healthy controls. We evaluated the AS patient's disease activity, functional ability, global assessment, and physical mobility and tested markers of systemic inflammation, erythrocyte sedimentation rate (ESR), and Creactive protein (CRP) levels. Serum levels of sRANKL [mean (SD), 4.75 (1.88) vs. 3.70 (1.14) pmol/l, p=0.015] and OPG [mean (SD), 5.18 (1.19) vs. 4.52 (0.85) pmol/l, p=0.026] were significantly higher in the 42 AS patients than the 26 healthy controls. Interestingly, serum OPG levels correlated significantly with ESR (r=0.417, p= 0.007), CRP (r=0.524, p