Measurement of renal function in kidney donors using serum cystatin C and beta(2)-microglobulin

Abstract

Background: The usefulness of serum cystatin C and serum beta(2)-microglobulin (B2M) as markers of glomerular filtration rate (GFR) were compared in kidney donors before and after nephrectomy.

Methods: Blood samples were taken from 28 donors (15 women and 13 men) for serum creatinine, urea, cystatin C and B2M estimation a median of 7 days before and 10 days after nephrectomy.

Results: Estimated GFR decreased from a median of 86.2 mL/min/1.73 m(2) to 60.3 mL/min/1.73 m(2), a median decrease of 28.6%. Serum creatinine increased by 40% and urea by 30.4%; serum cystatin C increased by 31.2% and serum B2M increased by 65.6%. Using published data on biological variation, critical values were calculated. An increase in serum creatinine above 18 micro mol/L detected the decline in renal function in 26/28 (92.9%) subjects. Increases in serum B2M greater than a critical value of 0.94 mg/L detected 24/28 (85.7%) of these subjects, but the critical value of 0.59 mg/L for cystatin C detected only 8/28 (28.6%).

Conclusion: Using critical values, serial measurement of serum creatinine was better than serum B2M in detecting reduced renal function. Because of its large intraindividual variation, serial serum cystatin C estimation was very poor in detecting reduced renal function.