Correlation between sclerostin level and radiographic changes in patients with ankylosing spondylitis

Abstract

To explore the serum level of sclerostin in ankylosing spondylitis (AS) patients and evaluate its diagnostic value and the relationship of sclerostin with inflammation and ossification process in AS. A total of 75 AS patients and 45 healthy controls were enrolled into this randomized controlled study. The clinical indices (age, gender, course of disease and disease activity), changes in radiographic studies and indices of bone metabolism or inflammation, including erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were evaluated or measured. The disease activity was assessed by Bath ankylosing spondylitis disease activity index (BASDAI), Bath ankylosing spondylitis functional index (BASFI), Bath ankylosing spondylitis metrology index (BASMI) and Bath arthritis spondylitis radiology index (BASRI). And radiographic changes were evaluated according to the modified Stoke AS spine score (mSASSS) and serum level of sclerostin was measured by enzyme-linked immunosorbent assay (ELISA). The relationship between sclerostin and clinical indices, radiographic scores and inflammatory indices was estimated by SPSS software and the diagnostic value of sclerostin analyzed by receiver operator characteristic (ROC) curve. The levels of ESR and CRP were higher in AS patients than those in healthy controls. However, serum sclerostin was lower (55.6±19.5 pmol/L) compared with healthy controls (78±27.6 pmol/L, P<0.01). ROC analysis revealed that the diagnostic specificity and sensitivity of sclerostin were 91.5% and 82.02% respectively with a cut-off of 62.75 pmol/L (Youden index 0.735, AUC 0.905, 95% CI 0.812-0.947). And the diagnostic validity was high. No significant correlation existed between sclerostin and ESR, CRP, BASDAI, BASMI and BASFI scores. ESR, CRP, BASDAI, BASMI and BASFI score were improved significantly in AS patients after anti-TNF treatment compared with baseline (P<0.01). There was little difference between BASRI and mSASSS score after anti-TNF treatment compared with baseline (P=0.19, 0.67). A significant negative correlation existed between the radiographic progression in spine of patients with AS and sclerostin serum levels (r=0.768, P<0.01). This correlation became stronger when radiographic scores rose (mSASSS>10, r=0.768, P<0.01) and it diminished when radiographic scores dropped (0<mSASSS<10, r=-0.097, P=0.43). Serum sclerostin may serve as a diagnostic biomarker of AS and progression index of ossification, especially in late stage of AS. A low serum level of sclerostin in the setting of AS is linked to greater structural damage.