Ann Lab Med 2018; 38(3): 261-265  
Evaluation of the 1B Equation to Estimate Glomerular Filtration Rate in Pediatric Patients with Cancer
Tae-Dong Jeong, M.D.1, Jaeryuk Kim, M.D.2, Woochang Lee, M.D.2, Sail Chun, M.D.2, Ki-Sook Hong, M.D.1, and Won-Ki Min, M.D.2
Department of Laboratory Medicine1, College of Medicine, Ewha Womans University, Seoul; Department of Laboratory Medicine2, University of Ulsan College of Medicine and Asan Medical Center, Seoul, Korea
Corresponding author: Won-Ki Min
Department of Laboratory Medicine, University of Ulsan College of Medicine and Asan Medical Center, 88 Olympic-ro 43-gil, Songpa-gu, Seoul 05505, Korea
Tel: +82-2-3010-4503
Fax: +82-2-478-0884
Received: July 24, 2017; Revised: September 4, 2017; Accepted: January 8, 2018; Published online: May 1, 2018.
© Korean Society for Laboratory Medicine. All rights reserved.

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The 1B equation is recommended for calculating the glomerular filtration rate (GFR) in children. Since few reports have evaluated the performance of the 1B equation, we investigated the performance of estimated GFR (eGFR) equations with the blood urea nitrogen (BUN) variable for pediatric cancer patients. In total, 203 children with cancer who underwent measured GFR (mGFR) assessment were enrolled. The median (range) mGFR and eGFR calculated using the updated Schwartz equation were 118 (43–241) and 135 (34–257) mL/min/1.73 m2, respectively. The bias, precision (root mean square error [RMSE]), and accuracy (P30, mGFR±30%) of three eGFR equations including updated Schwartz, 1B, and full age spectrum (FAS) were compared. The median bias (mL/min/1.73 m2) was: updated Schwartz, 8.5; 1B, -9.0; and FAS, 4.2. The biases for all three eGFR equations were significantly different from zero. The P30 was: updated Schwartz, 63.5%; 1B, 66.0%; and FAS, 66.0%. The RMSE was the lowest for the 1B equation (40.4), followed by FAS (42.3), and updated Schwartz (45.5). The median eGFR/mGFR ratio for the eGFR equations decreased with age and reduced kidney functions (i.e., increased creatinine and BUN concentrations). The bias may be further reduced by using the average from two equations, such as the updated Schwartz and 1B, or FAS equation, rather than using the updated Schwartz or 1B equation alone. The use of the 1B equation may underestimate the GFR. Using creatinine and BUN variables in the eGFR equation may yield a more accurate estimate of the GFR in pediatric cancer patients.
Keywords: 1B, Blood urea nitrogen, Children, Creatinine, full age spectrum, Glomerular filtration rate, updated Schwartz

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