Background
To evaluate the effect of treatment on bone biomarkers and explore whether bone biomarkers are associated with therapeutic response in rheumatoid arthritis (RA) patients treated with abatacept.
Methods
We enrolled 59 RA patients treated with abatacept from a multicenter prospective ultrasound cohort study of patients who received biologic or targeted synthetic disease-modifying antirheumatic drug (DMARD) therapy. We evaluated the patients' clinical disease activity and musculoskeletal ultrasound (MSUS) scores. The serum concentrations of five bone biomarkers were evaluated (dickkopf-1 [Dkk-1], sclerostin [SOST], osteocalcin [OC], osteopontin [OPN], and osteoprotegerin [OPG]) by multiplex bead assays at baseline, 3, and 6 months: the change over 6 months was defined as the Δ value. 'Power Doppler (PD) responder' was defined as a patient whose Δtotal PD score over 6 months was greater than the median change.
Results
Abatacept significantly improved clinical disease activity as well as the MSUS score over 6 months. Serum OPG was significantly elevated at 6 months after the introduction of abatacept (p = 0.016). The ΔSOST and ΔOPG values were negatively correlated with the Δtotal PD score (rs = − 0.31, p < 0.05 and rs = − 0.34, p < 0.01, respectively). The serum Dkk-1 at baseline was significantly lower in the PD responders (n = 30) compared to the non-PD responders (n = 29) (p = 0.026). A multivariate logistic regression analysis showed that the serum Dkk-1 at baseline (odds ratio 0.50, p = 0.043) was an independent predictor of PD responder status.
Conclusion
Serum levels of bone biomarkers may be useful for predicting RA patients' ultrasonographic response to abatacept.