Urinary glycosaminoglycan excretion in patients with rheumatoid arthritis and osteoarthritis: Correlation with disease activity

Abstract

The degradation products of proteoglycans are released from the cartilage matrix and appear in the synovial fluid, serum and urine. The aims of this study were to examine urinary glycosaminoglycan(GAG) levels in Rheumatoid Arthritis(RA) and Osteoarthritis(OA) patients and to investigate the relationship between disease activity and urinary GAG excretion. Twenty four hour urine specimens were collected from 34 normal controls, 34 patients with RA and 34 patients with OA. RA patients were divided into four groups by disease activity: remission, mild, moderate and severe. At each assessment, the following parameters of disease activity were recorded; duration of morning stiffness, erythrocyte sedimentation rate(ESR); tender and swollen joint number. OA patients were assessed clinically with radiological assessment of the affected joints and measurement of the ESR. All urine samples were stored at -70°C until assayed. DMB(dimethylmethylene blue) dye binding assay was used to measure GAG excretion. Urinary GAG levels were higher in patients who had RA(p<0.001) and OA(p<0.05) than the normal controls. There was a statistically significant correlation between GAG excretion and disease activity inpatients with RA. A higher mean GAG levels was observed in the patients with more severe RA. Urinary GAG excretion of OA patients were similar to the RA patients who were in remission. No significant correlations were found between the radiologic grade and the concentration GAG in patients with RA and OA. We concluded that measuring urinary GAG excretion in OA and RA patients may be useful in following cartilage damage and disease activity.