Barbara Ulibarri, Carlos Martinez Duncker*, Claudia Camarillo*, Enrique Omar Guadarrama, Pilar Garcia Roca**, Ricardo Munoz Arizpe**, Mara Medeiros**
Departamento de Nefrologia, Departamento Medicina Nuclear*, Laboratorio de Investigacion en Nefrologia**, Hospital Infantil de Mexico Federico Gomez, Mexico
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Abstract
The purpose of the study was to compare the GFR obtained with 99mTc DTPA against five other methods: the GFR measured by 24 hours creatinine clearance (Ccr), and four creatinine-based equations (Schwartz, Counahan-Barrat, Morris and Leger). A descriptive, cross-sectional study was performed in 42 renal transplant children; a 24 hours urine collection was obtained for creatinine clearance. A 99mTc-DTPA renal gammagram was performed the same day. The mean GFR (mL/min1.73m2BSA) obtained with 99mTc-DTPA was 66.9 ± 15, whereas by Ccr was 68.7 ± 24.4, by Schwartz formula 81.8 ± 16, by the Counahan-Barrat equation was 57.6 ± 13.6, by Morris equation 60.7 ± 14.5 and by Leger equation 73.2 ± 18. The predictive performance was evaluated calculating bias as mean prediction error (MPE) and precision (Mean Squared Error, MSE). The Schwartz formula had a MPE of 14.8 and MSE of 9223. The Ccr had a MPE of 1.7 and MSE of 132, Counahan-Barrat MPE -9.4, MSE 3727, Morris -6.28, MSE 1656, Leger -6.2 MSE 2000. Ccr had the lowest bias but is not precise to estimate GFR in renal transplant children. The Morris equation had better predictive performance in renal transplant children than the Schwartz, Counahan-Barrat and Leger equations.
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