Objectives: To explore the association between S100A8/A9 serum levels with clinical and structural characteristics of patients with established knee, hip, or hand osteoarthritis (OA).
Method: A cross-sectional exploratory study was conducted with 162 OA patients. Measures for pain, stiffness, and function included the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) questionnaire or the Australian Canadian Osteoarthritis Hand (AUSCAN) Index and for structural abnormalities, osteophytes and joint space narrowing grades. The association between S100A8/A9 and clinical or structural characteristics was analysed using linear regression or logistic regression where appropriate.
Results: The mean age of the OA patients was 56 years, 71% were female, and 61% had a Kellgren and Lawrence (K&L) score ≥ 2. The serum S100A8/A9 level did not differ between knee, hip, and hand OA patients and no association was found between serum S100A8/A9 and clinical characteristics. The serum S100A8/A9 level was negatively associated with the sum score of osteophytes after adjusting for sex and body mass index (BMI) [adjusted β -0.015, 95% confidence interval (CI) -0.030 to 0.001, p = 0.062] and positively associated with erythrocyte sedimentation rate (ESR) > 12 mm/h (adjusted OR 1.002, 95% CI 1.000-1.004 p = 0.049) for each increase in S100A8/A9 of 1 ng/mL. For hand OA patients, a negative association of S100A8/A9 with sum score of joint space narrowing was found (adjusted β -0.007, 95% CI -0.016 to 0.001, p = 0.099).
Conclusions: The results from this cross-sectional exploratory study do not support an important role for serum S100A8/A9 levels as a biomarker for clinical and structural characteristics in established knee, hip, and hand OA patients. The inverse association with structural abnormalities and the positive association with ESR may reflect inflammatory synovial processes in patients with OA before structural abnormalities occur.