Prognosis of clinical renal disease and incidence of new renal findings in patients with rheumatoid arthritis: follow-up of a population-based study.

The objective of this study was to assess the long-term prognosis of nephropathy findings and the incidence of new abnormal clinical renal findings in patients with rheumatoid arthritis (RA). The original population-based cross-sectional study of 604 RA patients was carried out in 1988, 103 nephropathy patients being found. Controls matched for age, sex, and duration of RA were selected from among RA patients with normal renal function and urinalysis in 1988. In 2003, a follow-up study was made of the 103 nephropathy patients and 102 controls, and the median follow-up time was 13 years. In the original nephropathy group, serum creatinine exceeded 200 mumol/l in 8% of the original isolated hematuria patients, in 30% of the isolated proteinuria patients, in 57% of the combined hematuria and proteinuria patients, but in none of the isolated chronic renal failure (CRF) patients (p = 0.001 for the difference). Probable or definitive renal amyloidosis was diagnosed in 19% of the nephropathy patients. Dialysis therapy was given to 10 out of the 103 nephropathy patients, nine of them belonging to the original isolated proteinuria or combined hematuria and proteinuria groups. There were six renal deaths among the nephropathy patients, and none in the controls. In the control group, new abnormal renal findings, in most cases mild, were detected in 28%. Serum creatinine exceeded 200 mumol/l in 4% of the controls, and dialysis therapy was given to 2% of the controls. Probable or definitive renal amyloidosis was diagnosed in 4% of this group. With regards to the development or progression of chronic renal failure, the long-term clinical prognosis of isolated hematuria and isolated CRF was found to be favorable. Proteinuria alone or combined with hematuria or CRF was related to evidently poorer prognosis.