Comparative optimization of alkaline phosphatase reference intervals using Hoffmann and refineR methods in age- and...

Alkaline phosphatase (ALP) is a routinely used biochemical marker whose concentrations are substantially influenced by age, growth, developmental stage, and sex. The use of an overly broad or unified reference interval (RI) may introduce bias into result interpretation.

A total of 345,469 ALP test results were included after data cleaning from a large-scale Laboratory Information System dataset. After stratification by age and sex, ALP RIs were estimated using the Hoffmann and refineR methods. Their stability, concordance with external RIs, and effects on abnormal result classification were compared. A small independent set of 50 healthy individuals was used for preliminary verification.

ALP exhibited an overall right-skewed distribution, with higher levels in children and adolescents than in adults. Supplementary pediatric subgroup analysis showed substantial heterogeneity within the original 0-18-year stratum, especially across childhood and pubertal age ranges. Males generally had higher ALP levels than females before 50 years of age, whereas this sex-related difference became less pronounced thereafter. ALP varied nonlinearly with age, reaching a peak during puberty, followed by gradual decline and stabilization in adulthood. Although the Hoffmann and refineR methods yielded similar lower-limit estimates, refineR provided a better fit to the right tail of the distribution, generated higher upper limits, showed closer agreement with external RIs, and produced a more balanced pattern of abnormal classification. No out-of-range results were observed in the preliminary verification set.

ALP interpretation should consider age and sex stratification. The refineR-derived intervals may provide a practical option for local RI optimization, pending further validation in larger independent cohorts.