Estimation of the glomerular filtration rate in people older than 85: Comparisons between CKD-EPI, MDRD-IDMS and BIS1 equations

Abstract

Background: The evidence of glomerular filtration rate (GFR) estimating with serum creatinine based formulae in the elderly population is scarce. The purpose of this study is to compare CKD-EPI, MRD4-IDMS and BIS1 equations to analyze correlation and concordance in a population older than 85 years old. Patients and methods: We designed a retrospective cross-sectional study, which included data from 600 patients older than 85 years. GFR was estimated by the following equations: CKD-EPI, MDR4-IDMS and BIS1, using as variables sex, age and serum creatinine concentration. Statistics analysis included Wilcoxon test, Bland–Altman plot, non-parametric Passing–Bablok method and kappa statistic (simple and weighted). Results: The patients’ median (range) age was 87 (interval 85–98). The median GFR (range) was 42.4 (5.2–127.4) mL/min/1.73 m2, when it was estimated with MDRD-IDMS, 40.0 (4.5–93.1) for CKD-EPI and 36.9 (7.6–83.7) for BIS1. The comparison of BIS1 and CKD-EPI and MDRD-IDMS using the Wilcoxon test was significant (p < 0.001). The regression analysis yielded the following equations: MDRD-IDMS = 1.025 × CKD-EPI + 1.360; BIS1 = 0.688 × CKD-EPI + 9.074 and BIS1 = 0.666 × MDRD-IDMS + 8.401. The weighted coefficient was 0.958 for the concordance between MDRD-IDMS and CKD-EPI, 0.812 for the concordance between MDRD-IDMS and BIS1 and 0.846 for CKD-EPI and BIS1. Conclusions: The GFR estimations obtained with BS1 equation are not interchangeable with MDRD-IDMS or CKD-EPI equations. BIS1 estimates lower GFR values than MDRD-IDMS and CKD-EPI and tends to classify the patients in a more advanced chronic kidney disease stage, especially for estimated GFR higher than 29 mL/min/1.73 m2.

Keywords

• Renal glomerular filtration
• Aged
• Aged 85 and over
• MDRD-IDMS
• CKD-EPI
• BIS1