Phenotypic Determinants and Clinical Implications of Creatinine-Cystatin C eGFR Discordance in Nigerian Adults

Abstract Background: Discordance between creatinine-based estimated glomerular filtration rate (eGFRcr) and cystatin C-based estimated glomerular filtration rate (eGFRcys) is increasingly recognised, but remains poorly characterised in African populations. We evaluated the magnitude, determinants, and clinical consequences of eGFR discordance among Nigerian adults with and without chronic kidney disease (CKD). Methods: In this cross-sectional study, 303 Nigerian adults were recruited at the University of Abuja Teaching Hospital, Nigeria, between February, 2020, and February, 2022. Serum creatinine and cystatin C were measured, and eGFR was calculated using the 2021 CKD-EPI equations. Agreement was assessed using Bland-Altman analysis and intraclass correlation coefficients (ICC). Multivariable regression identified determinants of biomarker variability and CKD stage reclassification. Results: Overall agreement between eGFRcr and eGFRcys was moderate (ICC 0.515), but differed markedly by CKD status (ICC 0.088 without CKD vs 0.804 with CKD). Among participants without CKD, 198 (81.8%) had absolute eGFR discordance of at least 15 mL/min per 1.73 m² and 145 (59.9%) had discordance of at least 30 mL/min per 1.73 m². Male sex was associated with lower odds of substantial discordance (OR 0.40, 95% CI 0.20–0.80). Overall, 153 (50.5%) participants were reclassified to a different KDIGO stage using eGFRcys, with upward reclassification predominating in those without CKD and downward reclassification in those with CKD. In participants without CKD, sex was the principal determinant of biomarker variability, whereas mean arterial pressure and age predominated in CKD. Each 1 mmHg increase in mean arterial pressure increased the odds of stage reclassification by 4% (aOR 1.04, 95% CI 1.02–1.07). Interpretation: eGFR discordance is common in Nigerian adults and reflects distinct biological processes according to CKD status. These findings support contextual interpretation of eGFR and selective use of cystatin C to improve CKD classification and clinical decision making in African populations.