To assess (a) the prevalence of microalbuminuria in patients with rheumatoid arthritis, (b) the association between urinary albumin excretion and disease activity as estimated by the erythrocyte sedimentation rate and C reactive protein (CRP), and (c) the association between urinary albumin excretion and treatment with antirheumatic drugs.
Sixty five patients with rheumatoid arthritis attending two rheumatology clinics were compared with 51 control subjects matched by age and sex. The controls consisted of 20 healthy subjects, 16 patients with osteoarthritis and 15 with non-articular rheumatism. Patients with hypertension, diabetes mellitus, or evidence of previous renal disease were not included. Urinary albumin was assayed by immunoturbidimetry in random urine samples on two occasions within seven months. The results were expressed as the ratio of urinary albumin to urinary creatinine ratio. Disease activity was assessed by the erythrocyte sedimentation rate and CRP. A drug history for the year before entry to the study was obtained for each patient.
Urinary albumin to creatinine ratio in patients with rheumatoid arthritis was significantly greater than in controls (p < 0.01). Microalbuminuria (urinary albumin to creatinine ratio 3-30 mg/mmol in either or both urine samples) was present in 27.7% of patients with rheumatoid arthritis and 7.8% of the control subjects. A significant relation was noted between urinary albumin to creatinine ratio and CRP, and the duration of disease. The number of patients treated with either gold or penicillamine was significantly greater in patients with microalbuminuria than in patients with normoalbuminuria.
Microalbuminuria is frequently present in patients with rheumatoid arthritis. Treatment with gold and penicillamine seems to increase the risk of developing microalbuminuria. Urinary albumin measured by immunochemical methods is a simple and sensitive test to detect early subclinical renal dysfunction and drug induced renal damage in rheumatoid arthritis. Urinary albumin excretion was found to be significantly correlated with CRP and may be a sensitive indicator of disease activity in patients with rheumatoid arthritis.