Serum levels of cartilage oligomeric matrix protein (COMP-TSP-5) in patients with rheumatoid arthritis stratified for functional class. <b>[Abstract in English]</b>

Abstract

Objective: To evaluate the serum levels of cartilage oligomeric matrix protein/thrombospondin-5 (COMP/TSP-5), a potential marker for articular damage, in patients with rheumatoid arthritis in different functional status and in healthy controls. Patients and methods: The study was cross-sectional. Fifty-eight patients with RA followed in the Outpatient Rheumatology Clinic of São Lucas Hospital of PUCRS comprised the target population. The Hochberg classification was utilized to estimate the functional status of patients with rheumatoid arthritis. The control group included 100 blood donors consecutively selected. Levels of COMP/TSP-5 were evaluated by immunoenzimatic assay (AnaMar Medical TM, Lund, Suecia). Levels above 12 U/I were considered positive. Comparison of groups was obtained by analysis of variation and a 5% significance levels was considered. Results: The medium age was 48±6 years for the control group and of 54±14 years for patients with rheumatoid arthritis (P>0.05). The female gender predominated in the group of rheumatoid arthritis (P<0.05). After adjustment for sex and age, the average levels of COMP/TSP-5 were 7.0 U/L (95%CI 6.1-7.9) for the control group and of 12.6 U/L (95%CI 11.1-14.1) for patients with rheumatoid arthritis (P<0.01). Among rheumatoid patients, 25 showed functional class I (43.1%), 14 functional class II (24.13%), 10 functional class III (17.2%), and 9 class functional IV (15.5%). With the exception of individuals with class functional III, patients from the other functional status presented higher frequency of positive test for COMP/TSP-5 as compared to controls (P<0.001). In each of the functional classes, the average levels of COMP/TSP-5 were significangly higher that those of the control group (P<0.05). The 28 rheumatoid patients with elevated COMP/TSP-5 were distributed uniformly in all 4 functional classes (P=0.65). Conclusion: The levels of COMP/TSP-5 were significantly higher in patientswith rheumatoid arthritis than in controls. The average serum levels of the protein remained elevated as compared to controls in all 4 functional classes of RA patients. Functional status does not seem to behave as a discriminative parameter for rheumatoid patients with elevated COMP/TSP-5 levels. KEY WORDS: ARTHRITIS, RHEUMATOID; BIOLOGICAL MARKERS; EXTRACELLULAR MATRIX PROTEIN; CARTILAGE; CHILD; ADOLESCENT; ADULT.