Relationship between serum hyaluronic acid level and disease activity in early rheumatoid arthritis.

OBJECTIVES To measure hyaluronic acid (HA) levels, which are raised in active rheumatoid arthritis (RA), in patients with early RA, and to assess the correlation with clinical and laboratory indices of disease activity and with subsequent radiographic erosive status. PATIENTS AND METHODS Patients fulfilling ACR criteria were recruited into a prospective cohort within 6 months of disease onset and reviewed every 6 months. An HA binding protein based sandwich ELISA was used to measure HA in 240 sera from 82 patients at regular intervals. RESULTS Patients had higher HA levels than age matched healthy blood donor controls (median 37.4 v 29.1 ng/ml, respectively, p<0.02), which increased with more prolonged disease. Baseline HA level correlated with measures of disease activity, including swollen and tender joint counts, HAQ, global assessments, ESR, and CRP; was higher in men; and increased with age. There was no relationship with HLA-DRB1 shared epitope or rheumatoid factor status. At 6 and 12 month follow up visits, HA levels were higher in patients who later developed erosions. However, a raised HA level was not a good predictor of erosions. CONCLUSIONS Serum HA level correlates with clinical and laboratory measures of disease activity in early RA, but is unlikely to be of practical use in clinical practice.