Correlation Between Serum Cartilage Oligomeric Matrix Protein (COMP), 25-Hydroxy Vitamin D, and Disease Activity in Patients with Knee Osteoarthritis

Background: The role of vitamin D and cartilage oligomeric matrix protein (COMP) in knee osteoarthritis (OA) still remains controversial. Objectives: This study aimed to evaluate serum COMP and 25-hydroxy vitamin D concentrations in patients with knee OA in comparison to healthy individuals and to find whether there is a relationship between serum COMP, 25-hydroxy vitamin D, and disease activity in knee OA. Methods: In a case-control study, 60 patients with knee OA were selected based on the criteria of the American College of Rheumatology referred to the Rheumatology Department of Tabriz University of Medical Sciences, Tabriz, Iran, from October 2017 to February 2018. Also, 28 healthy subjects matched regarding age and sex were selected. The patients were examined, and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC Index) was assessed. Serum levels of COMP and 25-hydroxy vitamin D were assessed by ELISA method. Results: The mean +/- SD age of the patients and controls was 57.60 +/- 10.63 and 56.46 +/- 5.58 years, respectively. Serum COMP was significantly higher in OA patients (40.82 +/- 10.04 pg/mL) than in healthy controls (27.01 +/- 9.64 pg/mL) (P < 0.001). There were no statistically significant differences in serum 25-hydroxy vitamin D between the patients and control subjects (P = 0.361). Significant correlations were found between serum COMP concentration with WOMAC score (r = -0.290, P = 0.025) as well as the grade of OA (r = 0.362, P = 0.004). No statistically significant correlations were found between serum 25-hydroxy vitamin D level with WOMAC score (r = 0.102, P = 0.438) and the grade of OA (r = -0.063, P = 0.630) as well as between serum COMP and 25-hydroxy vitamin D levels (P > 0.05). Conclusions: Based on the results of our study, Serum COMP levels correlated with disease characteristics in patients with osteoarthritis. Although further studies are needed to confirm our results, COMP may be used as a possible novel marker to measure osteoarthritis development and progression.