Cystatin C, an early indicator for incipient renal disease in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic disease requiring potential nephroto xic therapy with nonsteroidal antiinflammatory drugs (NSAIDs) and disease m odifying antirheumatic drugs (DMARDs), The rationale of our study was to ex amine the renal status of patients suffering from prolonged RA by means of plasma cystatin C, a new parameter of renal function. fifty-six patients af fected with RA for more than 5 years, and treated with NSAIDs for more than 50 months, were included in the study. Besides conventional markers of ren al function (i.e. plasma creatinine, estimated glomerular filtration rate, creatinine clearance), we analysed plasma cystatin C by an automated, nephe lometric immunoassay on a Behring nephelometer. Sixty percent of the RA pat ients exhibited elevated levels of plasma cystatin C, whereas only three ou t of 56 patients showed an elevated plasma creatinine, even though the crea tinine clearance was decreased in 57% of these patients. Cystatin C exhibit ed a by far better correlation with creatinine clearance than plasma creati nine. In conclusion, patients with prolonged RA for more than 50 months, sh ow a disturbed renal function despite normal plasma creatinine. Elevated cy statin C indicates such incipient renal disease, and is, not least because of a simple, well reproducible technique, more recommendable for screening purposes than tedious clearance determinations. Science B.V. All rights res erved.