Wu Zhifang

Evaluation of the estimated variables for scaling glomerular filtration rate of renal patients: A repeated measures-based method

Abstract Objective. Using a best variable to scale glomerular filtration rate (GFR) is important for clinical practice. The variables, estimated by equations regressed from a healthy population, are usually used in scaling GFR of renal patients. However, because the predicted variables may deviate in renal patients, it is necessary to verify whether these variables can be used to reduce the variability of GFR of renal patients. This study was designed to use repeated measures analyses to identify the best variable for scaling GFR of renal patients. Methods. Patients with non-obstructive renal diseases were enrolled in this study. The absolute GFRs of 99mTc-DTPA renography (gGFR) and plasma clearance (pGFR) were measured. The indices relating to between-subjects variability, such as Passing and Bablok regression, intraclass correlation coefficient (ICC) and concordance correlation coefficient (CCC) were used to identify the best variable from body surface area (BSA), extracellular fluid volume (ECV), lean body mass (LBM), total body water (TBW), body mass index (BMI), and metabolic rate (MR). Results. For the scaled indices related to between-subjects variability, ICC and CCC identified the same ranking sequence (BMI < LBMB(B; Boer) < LBMJ(J; James) < TBW < ECVB(B; Bird) < ECVS(S; Silva) < BSA < MR). In the Passing and Bablok regression, the ratio of residual standard deviation to pooled standard deviation (RSD/PSD) produced the same ranking sequence as that identified by ICC and CCC. Conclusion. The estimated metabolic rate can explain most between-subjects variability of GFR, and seems to be the best variable for scaling GFR of renal patients.

A step-by-step regressed pediatric kidney depth formula validated by a reasonable index

Abstract In predicting pediatric kidney depth, we are especially interested in that the errors of most estimates are within a narrow range. Therefore, this study was intended to use the proportion of estimates within a range of −5 to 5 mm (P5 mm) to evaluate the formulas and tried to regress a kidney depth formula for children. The enrolled children aged from 1 to 19 years were randomly sampled into group A and group B (75% and 25% of all recruits, respectively). Using data of the group A, the test formula was regressed by nonlinear regression and subsequently Passing & Bablok regression, and validated in group B. The Raynaud, Gordon, Tonnesen, Taylor, and the test formulas were evaluated in the 2 groups. Accuracy was evaluated by bias, absolute bias, and P5 mm; and precision was evaluated by correlation coefficient. In addition, root-mean square error was used as a mixed index for both accuracy and precision. Body weight, height, and age did not have significant differences between the 2 groups. In the nonlinear regression, coefficients of the formula (kidney depth = a × weight/height + b × age) from group A were in narrower 95% confidence intervals. After the Passing & Bablok regression, biases of left and right kidney estimates were significantly decreased. In the evaluation of formulas, the test formula was obviously better than other formulas mentioned above, and P5 mm for left and right kidneys was about 60%. Among children younger than 10 years, P5 mm was even more than 70% for left and right kidney depths. To predict pediatric kidney depth, accuracy and precision of a step-by-step regressed formula were better than the 4 “standard” formulas.

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.