Validation of child serum creatinine-based prediction equations for glomerular filtration rate

Abstract

Equations for estimating glomerular filtration rate (GFR) are vital in caring for patients with renal disease and the current standard, the Schwartz formula, lacks precision. We evaluated several child serum creatinine-based GFR prediction equations. Subjects aged 2-21 years who underwent iothalamate GFR (IoGFR) testing between 1999 and 2004 were studied retrospectively. GFR was estimated using: (1) Schwartz formula (SchwartzGFR), using a local k value; (2) Schwartz model (SchwartzMod) using regression-derived coefficients; (3) Leger GFR (LegerGFR) using original coefficients; and (4) Leger model (LegerMod) using regression-derived coefficients. Bias, precision, and diagnostic characteristics were evaluated. There were 195 subjects [61% male; mean (SD) age 12.4 (4.5) years; mean (SD) IoGFR 78.9 (33.4) ml/min per 1.73 m(2)]. Only the LegerGFR overestimated IoGFR (5.5 ml/min per 1.73 m(2)). Precision for all formulae was poor (95% limits of agreement approximately -40 to 40 ml/min per 1.73 m(2)), but >or=72% of estimates were within 30% of IoGFR. Sensitivities for detecting IoGFR <30 and 90 ml/min per 1.73 m(2) were highest using the SchwartzGFR (80%) and SchwartzMod (90%), respectively. The LegerGFR was most specific. Using local coefficients, the Schwartz and Leger models were imprecise estimates of GFR, but the Schwartz model was most unbiased and sensitive. Future research should derive more precise equations for GFR in children.

New Equations to Estimate GFR in Children with CKD

“…We found that the addition of gender and height (alone) significantly improved the eGFR. This model III, 30 and 10%, respectively, of the measured iGFR. To assess the goodness of fit of the lognormal model [i.e., log(iGFR) as a Gaussian variate], we allowed model III to have residual error distributed as a generalized gamma variate and found that the shape parameter was Ϫ0.0098 (95% confidence interval Ϫ0.23 to 0.21), consistent with the lognormal model being appropriate to describe the distribution of iGFR as it corresponds to the case of the shape parameter being equal to 0.…”

Renal Dysfunction and Elevated Blood Pressure in Long-Term Childhood Cancer Survivors

“…To assess glomerular function, we measured serum creatinine using an enzymatic, isotopic dilution mass spectrometry-traceable method (Roche P800, Roche Diagnostics, Almere, the Netherlands) and estimated the GFR using the Schwartz formula as adapted by Zappitelli for survivors up to 18 years of age (0.469 3 [height in cm/ serum creatinine in mg/dl]) (16). The Chronic Kidney Disease Epidemiology Collaboration formula was used for all adult survivors (17).…”

Ascertainment and Epidemiology of Acute Kidney Injury Varies with Definition Interpretation

“…Our rationale for evaluating the use of an estimated baseline eCCl of 120 ml/min per 1.73 m 2 is that the Schwartz eCCl overestimates true GFR by as much as 25% to 30% (16), and the presence of undetected chronic kidney disease in children is extremely rare; thus, an eCCl of 100 ml/min per 1.73 m 2 could substantially underestimate baseline renal function, resulting in an underestimate of AKI during admission. We then back-calculated the estimated SCr using the Schwartz formula (eCCl 100 and eCCl 120 ), as suggested by the original authors of the RIFLE criteria (17).…”