Cartilage oligomeric matrix protein in serum in systemic lupus erythematosus and knee osteoarthritis. Preliminary communication

The cartilage oligomeric matrix protein (COMP) is a glycoprotein, which occurs mainly in an articular cartilage. The amount of this protein increases under the influence of cytokines and growth factors. As a result of various diseases that cause damage to cartilage, fragments of matrix protein are released into synovial fluid and then into blood. The assessment of matrix protein level in serum, for example COMP, permits the establishment of the degree of cartilage damage in inflammatory joint diseases, and permits observation of the effectiveness of the treatment. Blood was collected from 30 systemic lupus erythematosus (SLE) patients, and from 30 patients with knee osteoarthritis (OA) who constituted the control group. Serum COMP level was determined using an inhibition enzyme-linked immunosorbent assay (ELISA). The average value of the serum COMP level in SLE patients was 11.3±3.7 U/l. According to correlation coefficients, serum COMP level is independent of patients’ age, disease duration and the clinical picture of SLE. No correlation was found between serum COMP level and bone mass density (BMD) changes. In SLE patients with decreased haemoglobin levels (<11.0 g/dl) values compared with patients with normal haemoglobin level, the serum COMP level was observed to be significantly higher (P<0.05). Both in SLE patients with erythrocyte sedimentation rate (ESR) values over 60 mm/h and in patients with ESR values below 60 mm/h, the serum COMP level was observed to be significantly higher (P<0.05). A significant positive correlation was found between serum COMP level and ESR value, as well as a number of thrombocytes. Negative correlation occurred between the serum COMP level and the value of haemoglobin. The average value of COMP in OA patients was 10.4±2.7 U/l. No correlation was found between serum COMP level and patients’ age and disease duration. There was correlation between the serum COMP level and the T-score value of densitometry examinations in OA patients. No statistical differences were found between the average serum COMP levels for SLE and OA patients.