Assessment of Four Different eGFR Equations in Older Turkish Adults

Age-related physiologic changes and comorbidities make it difficult to estimate the glomerular filtration rate(GFR) in older adults. Although inulin clearance is accepted as the gold standard for measuring GFR, it is impractical in clinical practice. A total of 228 patients who underwent a 24-hour creatinine clearance test for the measured GFR (mGFR) were included in the study.The estimated GFR(eGFR) was calculated according to the Modification of Diet in Renal Disease(MDRD) and Chronic Kidney Disease Epidemiology Collaboration(CKD-epi), Berlin Initiative Study-1(BIS-1) and Full Age Spectrum(FAS) formula. The medians of the differences between mGFR and each eGFR equation were used for assessing the bias, and the interquartile range(IQR) of the differences was used for expressing the precision of each equation. The mean age was 76.98±7.83 years and the frequency of female patients was 58.20%. In all patients, FAS[bias=0.40(1.09%), IQR= 26.55 (%52.49)] and BIS-1[bias=1.36(4.27%), IQR=26.71 (%55.28)] were less biased.In the mGFR≥60 mL/min/1.73 m2 subgroup, MDRD was the most precise[bias= -1.73(-1.69%), IQR=25.14 (%49.75)]. in four equations.In patients younger than 75 years, MDRD and CKD-epi equations were less biased, and the CKD-epi equation had the smallest IQR[bias=2.80(4.52%),bias= -2.93(-4.29%), IQR=32.97(49.94%)], whereas, in those older than 75 years, BIS-1 and FAS equations were less biased. However, for the patients 30≤mGFR<60 and mGFR<30 mL/min/1.73 m2, BIS-1 had the lowest bias and smallest IQRs[bias=3.49(7.81%),IQR=14.28(33.20%) and bias=7.60(40.11%), IQR=13.81(39.59%)]. In conclusion, BIS-1 and FAS equations were less biased in older patients with mGFR<60 mL/min/1.73 m2, and MDRD and CKD-epi were less biased in patients with mGFR≥60 mL/min/1.73 m2.