Abstract / Summary
Abstract Background Serum creatinine is routinely used to estimate the glomerular filtration rate (eGFR) but is strongly influenced by non-GFR determinants. Current guidelines therefore recommend incorporating cystatin C, alone or in combination with creatinine, to improve the accuracy of eGFR and chronic kidney disease (CKD) staging. Method We conducted a cross-sectional study of 721 adults aged 65 years and older with concurrent serum creatinine and cystatin C measurements at University Malaya Medical Centre, Kuala Lumpur, Malaysia. eGFR was calculated using the CKD-EPI 2009 creatinine, CKD-EPI 2021 creatinine, CKD-EPI 2012 cystatin C, CKD-EPI 2012 creatinine–cystatin C, and CKD-EPI 2021 creatinine-cystatin C equations. As no measured GFR was available, the analysis evaluated equation-to-equation agreement rather than accuracy against a criterion standard. Results The mean age was 74.6 ± 6.2 years, and 53.5% had diabetes. Relative to the CKD-EPI 2009 creatinine equation, the CKD-EPI 2012 cystatin C equation systematically returned lower eGFR (mean bias 16.7 mL/min/1.73 m²; ICC 0.669; 95% limits of agreement − 6.9 to 40.3) and up-staged 459 participants (63.7%) to more advanced CKD categories. Combined equations attenuated this effect (CKD-EPI 2021 creatinine-cystatin C: mean bias 5.6 mL/min/1.73 m²; ICC 0.923) while still up-staging 25.9%. Large negative discordance affected 244 participants (33.8%) and was independently associated with older age (odds ratio 1.060 per year), higher body mass index (odds ratio 1.075 per kg/m²), and diabetes mellitus (odds ratio 1.620). Conclusions In older Malaysian adults, the choice of filtration marker substantially alters CKD staging: cystatin C-based eGFR often reclassifies patients into more advanced stages, whereas combined equations provide more consistent, intermediate estimates.