Performance of creatinine and cystatin C-based equations to estimate glomerular filtration rate in African children with sickle cell anemia.

BACKGROUND

Serum creatinine (SCr), the most used biomarker to evaluate glomerular filtration rate (GFR), might be inaccurate in children with sickle cell anemia (SCA). In this context, cystatin C (SCys) could be of interest. This study evaluated the performance of commonly used SCr- and SCys-based estimated GFR (eGFR) equations in African children with SCA.

METHODS

This cross-sectional study included 109 steady-state children with SCA aged 3-18 years, from the Democratic Republic of Congo. Measured GFR (mGFR) was obtained using iohexol plasma clearance. eGFR was calculated using commonly used SCr- and SCys-based equations in children. The performance of these equations was evaluated by calculating the bias, precision, and accuracy within 30% (P30) of mGFR.

RESULTS

The mean age of participants was 9.9 ± 4.2 years, and 48.6% were female. The median mGFR was 142 (IQR 119-169) mL/min/1.73 m2. Of the equations studied, the FAS-Age SCr had the lowest bias (0.9 mL/min/1.73 m2). However, the 95% limit of agreement was very wide (-80.3 to + 81.6). SCr failed to rise in an age-dependent manner, reflecting a progressive loss of muscle mass or increased tubular secretion. All SCys-based equations underestimated GFR and failed to detect hyperfiltration, but there was no age-related change in bias.

CONCLUSION

These data show that all common eGFR equations using SCr or SCys poorly predict mGFR in African children with SCA. SCr-based equations potentially miss a decline in kidney function, which suggests that SCys could be the preferred marker in this population.