Kidney failure risk equation and early renal risk in adults with sickle cell disease: comparison with KDIGO classification using measured GFR

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Chronic kidney disease is a major complication of sickle cell disease (SCD), but early kidney injury frequently occurs despite preserved or increased glomerular filtration rate (GFR), potentially limiting the usefulness of conventional kidney failure prediction tools. We evaluated whether the Kidney Failure Risk Equation (KFRE) adequately reflects renal vulnerability in adults with SCD. In this multicenter cross-sectional study conducted in Kinshasa, Democratic Republic of the Congo, 241 adults with stable SCD underwent iohexol-measured GFR (mGFR) and albuminuria assessment. Renal risk was classified according to KDIGO criteria. The KFRE was calculated overall and in participants with CKD stage ≥3. Multivariable logistic regression identified factors independently associated with moderate-to-high renal risk. Overall, 35.7% of participants had moderate-to-high KDIGO renal risk. Despite this burden of renal risk, KFRE estimates remained very low overall and increased only in participants with CKD stage ≥3 (median risk: 5.98% at 2 years and 10.14% at 5 years). Increased renal risk was independently associated with vaso-occlusive crises (aOR 2.80, p = 0.012), leg ulcers (aOR 1.90, p = 0.030), stroke (aOR 2.66, p = 0.035), elevated LDH >220 U/L (aOR 3.19, p = 0.006), CRP ≥6 mg/L (aOR 3.04, p = 0.024), AST >40 IU/L (aOR 2.60, p = 0.002), and tricuspid regurgitant velocity ≥2.5 m/s (aOR 1.81, p = 0.041). More than one-third of adults with SCD had moderate-to-high renal risk despite preserved GFR. The discordance between KDIGO renal risk and KFRE estimates suggests that KFRE may underestimate early renal vulnerability in SCD. Measured GFR combined with albuminuria may improve early renal risk stratification and warrants prospective validation.