Serum cystatin C levels in children with sickle cell disease.

Patients with sickle cell disease (SCD) may develop kidney dysfunction from childhood. The purpose of this study was to examine the value of serum cystatin C as a marker for glomerular filtration rate (GFR) in children with SCD, as compared to serum creatinine and creatinine clearance (CrCl). Twenty children (ages 9-21, ten males) with SCD with and without albuminuria were studied. The mean serum cystatin for the whole group was 0.89 mg/l (0.5-1.7 mg/l). Mean serum cystatin C was significantly different among the children with proteinuria (n=4), microalbuminuria (n=5), and without albuminuria (n=11) (1.25 mg/l, 0.84 mg/l, and 0.78 mg/l, respectively). The mean GFR derived from serum cystatin was significantly different among these subgroups, becoming abnormal in the proteinuric cohort (63 ml/min per 1.73 m2), in contrast to 94 for the microalbuminuric, and 103 for the normal subgroups. Serum creatinine (mean: 0.58 mg/dl, range: 0.3-1.1) did not change significantly with the level of albuminuria. Mean CrCl remained normal to increased within the subgroups, (133 ml/min per 1.73 m2 for those with proteinuria, 144 for those with microalbuminuria, and 163 for the normal subgroup). We conclude that serum cystatin C correlates with the level of albuminuria and may be a reliable method to measure renal function in SCD.