Estimation of the Age-Dependent Decline of Glomerular Filtration Rate from Formulas Based on Creatinine and Cystatin C in the General Elderly Population

BACKGROUND/AIMS: To evaluate the performance of estimation formulas for glomerular filtration rate (GFR) based on creatinine and cystatin C in elderly. METHODS: This study includes 2,931 men and women comprising nine age cohorts (60-93 years) from a longitudinal population-based project in Sweden. The participants were divided into four age groups. GFR was estimated from four formulas: the Modification of Diet in Renal Disease (MDRD), CKD-EPI and Cockroft-Gault (CG) based on creatinine and one based on cystatin C (eGFR-CysC). CG was also adjusted for body surface area (BSA) to CG/BSA. RESULTS: CG, CG/BSA and eGFR-CysC yielded significantly lower GFR values compared to MDRD and CKD-EPI in the oldest persons (>80 years). A low GFR (<30 ml/min/1.73 m²) was demonstrated with MDRD in 3.3% (80-89 years) and in 6.3% (>90 years). With CG/BSA it was 8.0% (80-89 years) and 27.2% (>90 years), and with eGFR-CysC it was 12.1% (80-89 years) and 27% (>90 years), respectively. The individual formulas showed different eGFR in the four age cohorts and also different slopes by increasing age. CG/BSA and eGFR-CysC both show steeper declines than MDRD and CKD-EPI. CONCLUSION: Age-associated decline of renal function is common in elderly and increases immensely after the age of 80 years. More than 25% of the oldest demonstrate eGFR <30 ml/min/1.73 m². CG and eGFR-CysC yielded the highest prevalence of decline and MDRD the lowest.