Usefulness of serum cystatin-C as a marker of the renal function: a comparative evaluation with beta 2-microglobulin, alpha 1-microglobulin and creatinine

We evaluated the usefulness of cystatin-C as a marker of renal function. Serum cystatin-C level was measured using latex agglutination tests in 885 patients with various forms of renal disease and 200 healthy subjects. In addition to cystatin-C, serum beta 2-microglobulin, alpha 1-microglobulin and serum creatinine (Scr) were measured concomitantly in the same sample. The serum cystatin-C level inversely correlated more closely with creatinine clearance (Ccr) (r = -0.90) than serum beta 2-microglobulin (r = -0.85), alpha 1-microglobulin (r = -0.74) and Scr (r = -0.78). In patients with mildly impaired renal function (defined as Ccr 71-90 ml/min), a significant increase in cystatin-C level was observed in 24% of patients, whereas elevated beta 2-microglobulin and Scr were seen in 8% and elevated alpha 1-microglobulin was seen in 17%. In patients with normal renal function (defined as Ccr > or = 100 ml/min), increased cystatin-C level was observed in 7% of patients, whereas beta 2-microglobulin was seen in 2%, Scr in 2% and alpha 1-microglobulin in 11%. These data suggest that cystatin-C is a better marker of glomerular filtration than beta 2-microglobulin, alpha 1-microglobulin and Scr. Moreover cystatin-C measurement offers improved clinical sensitivity as a screening test for early renal damage.