Establishment of pediatric reference intervals for myocardial enzymes in Beijing using an indirect method

Abstract Background Pediatric myocardial enzyme reference intervals (RIs) are crucial for diagnosing myocardial injury in children, but China currently lacks pediatric-specific RIs for most cardiac biomarkers, relying instead on adult standards. This study aimed to establish pediatric serum RIs for five myocardial enzymes (AST, LDH, HBDH, CK, and CK-MB) in Beijing using an indirect Hoffmann method. Methods A retrospective analysis was conducted on 93,196 test records from children aged 28 days to 18 years who visited the Capital Institute of Pediatrics between January 2021 and November 2024. After rigorous exclusion of individuals with diseases affecting cardiac, hepatic, respiratory, skeletal muscle, or metabolic functions, data were stratified by age and sex. The Hoffmann method was used to establish RIs (2.5th–97.5th percentiles, or 95th percentile upper limit for CK-MB), with partitioning validated by Harris-Boyd testing. RIs were compared with Chinese national standards (WS/T 780–2021) and international CALIPER data. Results Final RIs were derived from 76,730–87,265 valid cases per analyte. All five enzymes showed significant age dependency and post-pubertal sexual dimorphism. AST, LDH, and HBDH declined with age and were lower in females after 12 years. CK decreased sharply in early childhood, plateaued from 2–12 years, and increased in males after 12 years. CK-MB was elevated before age 4 years and decreased thereafter. Age- and sex-specific RIs were established for each analyte. AST RIs aligned closely with WS/T 780–2021 (relative bias within reference change value limits). Comparisons with CALIPER showed good consistency, with minor differences attributed to analytical platforms and population characteristics. Conclusions This study provides pediatric-specific RIs for five myocardial enzymes in Beijing children aged ≥ 28 days using an indirect method. These RIs fill a critical clinical gap in China, enabling more accurate diagnosis and management of pediatric myocardial injury. Future work should extend to neonates and validate these RIs across multiple centers.