Serum Cystatin C as a Superior Renal Function Marker Compared to Creatinine in Elderly Patients in Osun State

Serum creatinine is the conventional marker of renal function in clinical practice, but its sensitivity is compromised in elderly patients with reduced muscle mass, making cystatin C a potentially superior alternative. This study compares serum cystatin C and creatinine-based eGFR estimates as indices of renal function in elderly patients in Osun State, South West Nigeria. A cross-sectional analytical design was adopted, recruiting 150 patients aged 65 years and above from a geriatric clinic. Serum cystatin C was measured by immunoturbidimetry, and creatinine-based eGFR was calculated using the CKD-EPI creatinine equation. Cystatin C-based eGFR was estimated using the CKD-EPI cystatin C equation and the combined creatinine-cystatin C equation. Agreement between estimates was evaluated by Bland-Altman analysis and intraclass correlation. Body mass index, handgrip strength, mid-upper arm circumference, and serum albumin were used as indices of muscle mass to characterise the creatinine-muscle mass confound. The study identifies patient subgroups in which cystatin C-based eGFR most significantly reclassifies CKD stage compared to creatinine-based methods. Findings will contribute to evidence-based recommendations for cystatin C adoption in geriatric renal assessment in South West Nigeria. Keywords: cystatin C, renal function, elderly patients, CKD staging, Osun State.