A prospective study of renal disease in patients with early rheumatoid arthritis

Objectives-This prospective study was designed to clarify the frequency, ca uses, and clinical course of renal disease in patients with early rheumatoi d arthritis (RA). Methods-235 patients (185 women, mean age 49.4 years) with early RA of less than one year's duration were enrolled and assessed monthly. Proteinuria w as defined as a positive dipstick result and microscopic haematuria was def ined as the presence of greater than or equal to5 red blood cells per high power field. Urinary abnormalities lasting three months or longer were defi ned as persistent abnormalities. Results-At entry, 40 patients exhibited haematuria, two had a raised serum creatinine concentration, and none had proteinuria. During the observation period (average 42 months), persistent haematuria was found in 43, persiste nt proteinuria in 17, and a raised serum creatinine concentration in 14 pat ients. Persistent proteinuria was caused by drugs in 14 of 17 patients and disappeared in most cases. Risk factors for drug induced proteinuria includ ed a raised C reactive protein and erythrocyte sedimentation rate and age o ver 50 at entry. Drugs resulted in a raised serum creatinine concentration in eight of 14 patients. The incidence of haematuria at entry did not diffe r among patients who had been treated with non-steroidal antiinflammatory d rugs, disease modifying antirheumatic drugs, or no drugs. In some patients with isolated haematuria, the haematuria appeared when the activity of RA w as high and resolved when it was low. Conclusions-This study suggests that a raised serum creatinine concentratio n or persistent proteinuria in patients with early RA is predominantly drug related whereas, in contrast, isolated haematuria is more directly associa ted with the activity of the disease process.