Assessment of renal function in geriatric palliative care patients - comparison of creatinine-based estimation equations.

Abstract

BackgroundRenal function impairment is common in geriatric palliative care patients. Accurate assessment of renal function is necessary for appropriate drug dosage. Several equations are used to estimate kidney function.Aims1) To investigate the differences (Δ) in kidney function assessed with simplified Modifi-cation of Diet in Renal Disease (MDRD), Berlin Initiative Study (BIS1), and Cockcroft–Gault (C-G) formulas in geriatric palliative care patients, and 2) to assess factors that may influence these differences.MethodsA retrospective analysis of data of patients aged ≥70 years admitted to a palliative care in-patient unit. The agreement between C-G, MDRD, and BIS1 equations was assessed with Bland–Altman analysis. Partial correlation analysis was used to analyze factors influencing the discordance.ResultsA total of 174 patients (67 men; mean age 77.9±5.8 years) were enrolled. The mean Δ MDRD and C-G was 18.6 (95% limits of agreement 55.3 and −18.2). The mean Δ BIS1 and C-G was 6.1 (25.7 and −13.5), and the mean Δ MDRD and BIS1 was 12.5 (40.6 and −15.6). According to the National Kidney Foundation classification, 61 (35.1%) patients were differently staged using MDRD and C-G, whilê20% of patients were differently staged with BIS1 and C-G and MDRD and BIS1. Serum creatinine (SCr) and body mass index (BMI) had the most important influence on variability of Δ MDRD and C-G (partial R2 37.7% and 28.4%). Variability of Δ BIS1 and C-G was mostly influenced by BMI (34.8%) and variability of Δ MDRD and BIS1 by SCr (42.2%). Age had relatively low influence on differences between equations (3.1%–9.5%).ConclusionThere is a considerable disagreement between renal function estimation formulas, especially MDRD and C-G in geriatric palliative care patients, which may lead to errors in drug dosage adjustment. The magnitude of discrepancy increases with lower SCr, lower BMI, and higher age.