Background: The usefulness of serum cystatin C and serum
β
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
m2 to 60.3 mL/min/1.73 m2, 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 µmol/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.
