Serum cystatin C--a superior marker of rapidly reduced glomerular filtration after uninephrectomy in kidney donors compared to creatinine.

Aims: Acute renal failure (ARF), defined by a rapid decrease of glomerular filtration rate (GFR), is associated with high mortality. Early and accurate detection of decreasing GFR is critical to prevent the progression of ARF and to potentially improve its outcome. Serum creatinine, the conventional GFR marker, has major limitations. We prospectively evaluated whether serum cystatin C detected a rapid GFR decrease earlier and more accurately than serum creatinine.

Methods: In ten patients undergoing nephrectomy for living related kidney transplantation, serum creatinine and cystatin C were determined daily. The decrease of GFR was quantitated preoperatively by creatinine clearance and MAG3 scintigraphy. The GFR decrease was defined by a 50-100% increase of cystatin C or creatinine from preoperative values. Ten patients without renal impairment served as controls.

Results: Initially, patients had a creatinine clearance of 105 +/- 14 ml/min/1.73 m2. Due to nephrectomy, patients lost 45 +/- 3% of their renal function. Serum cystatin C significantly increased already one, serum creatinine two days after nephrectomy. Cystatin C demonstrated an increase by 50-100% 1.4 +/- 0.9 days earlier than creatinine (p = 0.009). Serum cystatin C performed well detecting the GFR decrease with higher diagnostic values compared to creatinine. This was indicated by a sensitivity of 50, 70 and 80% of cystatin C to detect the GFR decrease on the three days following nephrectomy.

Conclusions: Serum cystatin C detects rapid GFR decreases one to two days earlier than creatinine. Cystatin C is an early and accurate marker to detect rapid GFR decreases as in ARF.