Influence of Weight-Age Normalization on Glomerular Filtration Rate Values of Renal Patients: A STROBE-Compliant Article

Abstract

To explore whether weight-age (W-A) could be applied in clinical practice, this study was designed to verify the normalization ability of W-A by the data from another medical center, and to access the influence of the normalization on glomerular filtration rate (GFR) values in renal patients.Both plasma clearance (pGFR) and camera-based (gGFR), which were separately scaled to W-A and body surface area (BSA), were measured for patients with diffuse renal diseases. The patients (n = 298) were stratified according to the Chinese body mass index (BMI) criteria and were staged according to the Kidney Disease Outcome Quality Initiatives guideline based on gGFR and pGFR separately.The indices of intraclass correlation coefficient (ICC), concordance correlation coefficient (CCC), and ratio of residual standard deviation to pooled standard deviation (RSD/PSD) suggested that, for all patients and each BMI stratum, W-A was obviously better than BSA in scaling GFR. Both under pGFR or gGFR renal stages, only small amount of the patients encountered stage migrations from BSA to W-A scaled stages. The differences between any 2 of the unscaled, BSA scaled, and W-A scaled gGFR (or pGFR) were not obviously changed. Additionally, in some strata, W-A normalization is better than BSA normalization in decreasing the median bias between pGFR and gGFR.W-A is better than BSA in scaling GFR without obvious modifying GFR values and can be applied in routine clinical practice.

FIGURE 1

Bland–Altman plots for paired GFRs (mL/min). From the top to the bottom, the plots are for unscaled, BSA and W-A scaled GFRs, respectively. The x-axis and y-axis represent the mean and difference between paired GFRs, respectively. The full line is the mean difference, and the area between the broken lines is the 95% confidence interval. BSA = body surface area, GFR = glomerular filtration rate, W-A = weight-age.

FIGURE 2

Evaluation of normalization ability. The indices for BMI strata are plotted as estimated values with 95% CI. BMI = body mass index, CI = confidence interval.

FIGURE 3

Influence of normalization on GFR values. From the first to the third row, plots are for the difference of paired GFRs, the difference of pGFR before and after normalization, and the difference of gGFR before and after normalization, respectively. Median bias is plotted as estimated value with 95% CI, and IQR and RMSE are plotted as the calculated value only. CI = confidence interval, GFR = glomerular filtration rate, gGFR = camera-based glomerular filtration rate, IQR = interquartile range, pGFR = plasma clearance glomerular filtration rate, RMSE = root-mean square error.