Abstract
BackgroundCreatinine clearance (CrCl) based on 24 h urine collection is an established method to determine glomerular filtration rate (GFR). However, its measurement is cumbersome and the results are frequently inaccurate. The aim of this study was to develop an alternative method to predict CrCl and urinary protein excretion based on plasma creatinine and the quantification of muscle mass through bioimpedance analysis (BIA).MethodsIn 91 individuals with normal and impaired renal function CrCl was measured from 24 h urine excretion and plasma creatinine concentration. A model to predict 24 h-creatininuria was developed from various measurements assessing muscle mass such as body cell mass (BCM) and fat free mass (FFM) obtained by BIA, skinfold caliper and other techniques (training group, N = 60). Multivariate regression analysis was performed to predict 24 h-creatininuria and to calculate CrCl. A validation group (N = 31) served to compare predicted and measured CrCl.ResultsOverall (accuracy, bias, precision, correlation) the new BIA based prediction model performed substantially better compared with measured CrCl (P15 = 87 %, bias = 0, IQR of differences = 7.9 mL/min/1.73 m2, R = 0.972) versus established estimation formulas such as the 4vMDRD (P15 = 26 %, bias = -8.3 mL/min/1.73 m2, IQR = 13.7 mL/min/1.73 m2, R = 0.935), CKD-EPI (P15 = 29 %, bias = -7.0 mL/min/1.73 m2, IQR = 12.1 mL/min/1.73 m2, R = 0.932, Cockcroft-Gault equations (P15 = 55 %, bias = -4.4 mL/min/1.73 m2, IQR = 9.0 mL/min/1.73 m2, R = 0.920). The superiority of the new method over established prediction formulas was most obvious in a subgroup of individuals with BMI > 30 kg/m2 and in a subgroup with CrCl > 60 mL/min/1.73 m2. Moreover, 24 h urinary protein excretion could be estimated accurately by normalization with 24 h-creatininuria derived from BIA based BCM.ConclusionPrediction of CrCl based on estimated urinary creatinine excretion determined from measurement of BCM by BIA technique is both accurate and convenient to quantify renal function in normal and diseased states. This new method may become particularly helpful for the evaluation of patients with borderline renal insufficiency and/or with abnormal body composition.
Highlights
Creatinine clearance (CrCl) based on 24 h urine collection is an established method to determine glomerular filtration rate (GFR)
Prediction of CrCl based on estimated urinary creatinine excretion determined from measurement of body cell mass (BCM) by bioimpedance analysis (BIA) technique is both accurate and convenient to quantify renal function in normal and diseased states
In the training group significant correlations with a Pearson’s correlation coefficient (R) beyond 0.5 with 24-h urine creatinine (24hU-Cr) excretion were detected for the following parameters: fat free mass (FFM) and BCM detected by whole body bioimpedance analysis, FFM obtained by Omron® BIA handheld device as well as for body weight, body height, estimated body surface area and lean body mass calculated from skin fold measurements
Summary
Creatinine clearance (CrCl) based on 24 h urine collection is an established method to determine glomerular filtration rate (GFR). GFR, can be determined fairly accurate and non-invasive by measuring creatinine clearance, which requires a 24 h urine collection. This method, has been replaced widely in clinical practice by estimating GFR using established formulas due to simplicity and ease of use [1, 2]. The Cockcroft-Gault formula on the other hand is less precise in predicting renal function in cases of advanced kidney failure This formula overestimates GFR slightly because it determines CrCl [3,4,5,6,7,8]
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