Establishment of Sex- and Age-Specific Pediatric Alkaline Phosphatase Reference Intervals by Indirect Methods

Background: Establishing pediatric reference intervals using the direct method is often limited by the challenges of specimen collection and associated costs.As an alternative, the indirect method enables reference interval estimation without the need for additional specimen collection by utilizing data accumulated in the laboratory information system (LIS).Alkaline phosphatase (ALP) levels show dynamic physiological variations according to sex and age.This study aimed to establish sex-and age-specific Korean pediatric serum ALP reference intervals using an indirect method based on hospital LIS data.Methods: ALP and six additional chemistry test results from 34,211 pediatric patients were retrospectively collected from the Ajou University Hospital LIS between July 2017 and June 2024.All measurements were performed on a Roche Cobas 8000 c702 analyzer.Data with non-Gaussian distributions were normalized using the Box-Cox transformation, and reference intervals were estimated using statistical methods based on the transformed data.Reference intervals were stratified by sex and further divided into four age groups within each sex, resulting in eight subgroups.Results: The estimated pediatric ALP reference intervals were as follows: Males, 0-9 years (153-390 U/L), 10-12 years (169-499 U/L), 13-14 years (116-499.1U/L), and 15-17 years (72-325.5 U/L); Females, 0-9 years (163-427 U/L), 10-12 years (147-443.4U/L), 13-14 years (64.5-328.9U/L), and 15-17 years (45.8-213.1 U/L).Conclusions: Sex-and age-specific pediatric ALP reference intervals were successfully established using an indirect method.These reference intervals may support clinical interpretation and provide updated baseline information for pediatric clinical practice in Korea.