A Comparison of the Accuracy of Different Single Plasma Sample Methods for Measuring Glomerular Filtration Rate Using 51 Cr-EDTA in Children

Abstract

Purpose

Among the different methods of measuring glomerular filtration rate (GFR) using ⁵¹Cr-ethylenediaminetetraacetic acid clearance, the two-plasma-sample method (TPSM) is widely used, and highly accurate. The single-plasma-sample method (SPSM) is occasionally used for simplicity, at the expense of accuracy. Our aims were (1) to investigate the correlation and (2) to compare the accuracy of six known SPSMs in pediatric patients in reference to TPSM.

Methods

We retrospectively reviewed 122 pediatric cases (65 boys, age 7.3 ± 4.6 years) and analyzed 307 GFR measurements. SPSMs included Groth and Aasted at 120 min, Ham at 120 min, Christensen and Groth at 120 and 240 min, and Jacobsson at 120 and 240 min. Reference GFR (GFR_ref) was defined using TPSM GFR corrected by the Jodal and Brochner-Mortensen equation. GFR_ref < 30 mL min⁻¹ 1.73 m⁻² were excluded. The standard error of the estimate (SEE) and the number of cases with differences > 10% (N_10%) were used to evaluate accuracy.

Results

SPSMs generally correlated well with GFR_ref (r = 0.92~0.99) and were relatively accurate (SEE = 9.21~15.60). Groth and Aasted showed the smallest SEE, while Jacobsson at 240 min showed the smallest N_10% for all GFR_ref ranges. As for the decreased GFR_ref, Ham was most accurate followed by Jacobsson at 240 min.

Conclusions

Jacobsson at 240 min provided good accuracy in all GFR_ref ranges and was well correlated with TPSM. Jacobsson at 240 min might be the most appropriate method to substitute for TPSM in pediatric patients. Ham could be an alternative in patients with impaired renal function.

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