Reference ranges for 51Cr-EDTA measurements of glomerular filtration rate in children.

Background: 51Cr-Ethylenediaminetetraacetic acid (51Cr-EDTA) is widely used to measure the glomerular filtration rate (GFR) in children and adults.
Aim: To produce paediatric reference data for use with the British Nuclear Medicine Society (BNMS) GFR guidelines.
Methods: This was a retrospective study of children and adolescents, aged 0-17 years, undergoing combined 99mTc-dimercaptosuccinic acid (99mTc-DMSA) scintigraphy and GFR examination. GFR was evaluated from Cr-EDTA plasma clearance using blood samples taken at 2, 3 and 4 h according to the methods set out in the BNMS GFR guidelines. 99mTc-DMSA images were reviewed to identify children with normal scans.
Results: Of the 45 children having a combined 99mTc-DMSA and GFR investigation, 27 (12 females, 15 males) had a normal scan result. The mean GFR (standard deviation) in the 24 subjects aged 2-17 years was 109.5 (16.8) ml . min(-1) . (1.73 m2)(-1). This compared with a predicted figure of 107.0 (17.0) ml . min(-1) . (1.73 m2)(-1) when the paediatric reference range published by Piepsz et al. was adjusted to be consistent with the BNMS GFR guidelines. When the GFR results in the present study were calculated according to the single-sample and two-sample methods used by Piepsz et al., there was close agreement with the results obtained in the latter study [116.7 (24.2) vs. 114.7 (25.8) ml . min(-1) . (1.73 m2)(-1)]. Children with abnormal 99mTc-DMSA scans had significantly lower GFR than those with normal scans (P=0.003).
Conclusion: There is a consistent difference between the GFR results in children with normal 99mTc-DMSA scans obtained in the present study and the unadjusted results of Piepsz et al. that can be explained by the different methods of calculating GFR in the two studies. Given the larger number of children in the latter study, it is proposed that centres evaluating GFR according to the BNMS method should adopt the Piepsz et al. reference range adjusted for consistency with the BNMS guidelines. This gives a mean GFR (SD) in children of 2 years and over of 107 (17) ml . min(-1) . (1.73 m2)(-1).