The Association between Saliva and Serum Vitamin D with Knee Osteoarthritis

Background: The incidence of osteoarthritis (OA) is high in patients suffering from 25-hydroxyvitamin D3 (25(OH)D) deficiency. The goal of this study is to examine the association between saliva and serum 25(OH)D and knee OA. Methods: Serum and saliva 25(OH)D levels of 30 patients with knee OA and 30 matched healthy people in a control group were measured by ELISA. Knee pain was assessed by Western Ontario and McMaster Universities Arthritis Index (WOMAC). Data were analyzed through student’s t-test, Pearson correlation test and receiver operating characteristic (ROC). Results: The mean serum and saliva 25(OH)D levels were lower in knee OA group than the healthy group. WOMAC negatively correlated with serum (r = -0.37; P = 0.02) and with unstimulated (r = -0.30; P = 0.04) saliva 25(OH)D. The unstimulated saliva 25(OH)D cutoff value was 27.8 pg/m1 regarding the diagnosis of knee OA. Conclusion: Serum 25(OH)D levels were positively associated with saliva 25(OH)D, and 25(OH)D level in saliva, as in serum, was low in knee OA.