Retrospective Beijing study establishes pediatric reference intervals for five enzymes

Researchers in Beijing have established age- and sex-specific reference intervals for five myocardial enzymes in children aged 28 days to 18 years, providing population-based benchmarks for interpreting blood-test results. After rigorous exclusions, the final analysis retained between 77,684 and 84,719 valid cases for each enzyme. The investigators analyzed test records collected at the Capital Institute of Pediatrics from January 2021 through November 2024.

They excluded individuals with diseases affecting cardiac, hepatic, respiratory, skeletal-muscle or metabolic functions before stratifying the remaining data by age and sex. This was an indirect study design, using suitable observations from an existing clinical database rather than prospectively recruiting a new healthy pediatric cohort. All five myocardial enzymes showed significant age dependence, and all exhibited post-pubertal sexual dimorphism.

AST, LDH and HBDH concentrations declined with age and were lower in females after age 12. CK behaved differently: its concentration decreased sharply during early childhood, plateaued from ages 2 to 12, and increased in males after age 12. CK-MB concentrations were highest before age 4 and decreased thereafter.

The findings show that pediatric reference intervals for these enzymes cannot be represented adequately by a single range across all ages, and that sex-specific partitions were important after puberty. The researchers applied the Hoffmann method to estimate the reference limits from the filtered clinical records. The intervals for AST, LDH, HBDH and CK covered the 2.5th through 97.5th percentiles, while CK-MB was assessed using a 95th-percentile upper limit.

Uncertainty around the limits was estimated with 1,000 bootstrap resamples, yielding 90% confidence intervals. The selected age and sex partitions were evaluated with Harris–Boyd testing. The resulting AST intervals showed good consistency with the Chinese national standard WS/T 780-2021 by bias-ratio analysis.

Comparisons with international CALIPER data also showed good agreement, with minor differences attributed to analytical platforms, reagent composition and population characteristics. The study addresses a gap in Chinese pediatric laboratory medicine, where pediatric-specific reference intervals have been unavailable for most of these cardiac biomarkers and adult standards have often been used instead. The authors said future work should extend the reference data to neonates, validate the intervals across multiple centers and analytical platforms, and compare methods for establishing pediatric reference intervals.

Within the studied Beijing population, the age- and sex-specific limits offer a detailed framework for interpreting pediatric AST, LDH, HBDH, CK and CK-MB measurements.

Subject of Research: Pediatric reference intervals for five myocardial enzymes in a Beijing retrospective cohort

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

Article References: Ge, M., Li, J., Song, Q., Guo, Q., Li, J., & Ma, L. (2026). Establishment of pediatric reference intervals for myocardial enzymes in Beijing using an indirect method. BMC Pediatrics. https://doi.org/10.1186/s12887-026-07615-7

Image Credits: AI Generated

DOI: 10.1186/s12887-026-07615-7

Keywords: pediatric reference intervals, myocardial enzymes, AST, LDH, HBDH, creatine kinase, CK-MB, Hoffmann method, Beijing children, laboratory medicine, Establishment, pediatric