Performance of creatinine and cystatin C-based equations for estimating high levels of glomerular filtration rate in Congolese adults with sickle cell disease

Introduction Sickle cell disease (SCD) carries a high risk of chronic kidney disease, necessitating accurate glomerular filtration rate (GFR) monitoring. This study evaluated the performance of creatinine-based (eGFRcrea), cystatin C-based (eGFRcys), and combined (eGFRcrea+cys) equations against directly measured GFR (mGFR). Methods Clinically stable Congolese adults with SCD were recruited in 13 medical centers from Kinshasa. GFR was measured using iohexol plasma clearance. We compared the bias, precision, and accuracy of Chronic Kidney Disease Epidemiology (CKD-EPI) and European Kidney Function Consortium (EKFC) equations. Results Among 207 patients included (24 [20;31] years and 58% of women), mean mGFR was 129±38mL/min/1.73m² with 41% of patients hyperfiltrating (mGFR>135mL/min/1.73m²). Among eGFRcrea equations, CKD-EPI was superior in hyperfiltrating patients, while EKFC performed better in normofiltrating patients. However, all eGFRcrea equations were suboptimal with only around 80% of eGFR results within 30% of measured GFR. Cystatin C-based equations showed severe underestimation and poor accuracy. Combined equations offered no clear added value. Conclusion All estimated GFR equations were suboptimal in this young SCD population, with cystatin C performing particularly poorly. Given the limitations of current biomarkers, measuring GFR by a reference method remains the recommended standard. However, given the cost and logistical challenges of measured GFR in low-income settings, relying on EKFCcrea for normofiltrating patients and on CKD-EPIcrea for hyperfiltrants appears to be a more feasible and pragmatic approach.