Discrepancy Between Equations Estimating Kidney Function in Geriatric Care: A Study of Implications for Drug Prescription

[Estimation of glomerular filtration rate in the elderly patient: Clinical implications in the use of antibiotics]

INTRODUCTION

In elderly, impaired kidney function may lead to relevant clinical implications, especially in drug dosage. There is no consensus on the best formula to estimate glomerular filtration rate (GFR) in this context. While the Cockcroft-Gault (CG) equation is the most used one in drug development, the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation is the most employed by clinical laboratories. The objective of this study is to analyze the differences and implications of using one or another equation when adjusting the dose of antibiotics.

MATERIAL AND METHODS

Cross-sectional study performed in patients older than 80 years admitted to an acute geriatric unit for infectious disease. Socio-demographic, functional, clinic, assistance and laboratory variables were gathered, calculating GFR according to CG and CKD-EPI. A concordance study between both equations, bivariate analysis and multiple linear regression were carried out.

RESULTS

100 patients were recruited, with mean age 88.5±4.2 years, and 54% women. A relative overestimation of 13.63mL/min was observed in GFR according to CKD-EPI, with a low-moderate concordance between both formulas. Greater need for dose adjustment of antibiotics with GC than with CKD-EPI was detected (38% vs. 23%; P<.001), as well as dosage discrepancies, especially with levofloxacin.

CONCLUSIONS

Both equations are not interchangeable in the elderly. When used to adjust antibiotic dose, CKD-EPI may overestimate GFR and may cause an increase in adverse reactions. Further studies should be carried out with the aim of reaching a consensus on the most appropriate equation for the elderly patient.