Alkaline phosphatase: reference interval transference from CALIPER to a pediatric Brazilian population

ABSTRACT Introduction: Interpreting laboratory tests requires reference intervals (RI) that may vary between different populations. For the diagnosis of hypophosphatasia (HPP), lower limits of alkaline phosphatase (ALP) levels must be determined. Objective: To transfer the RI findings for ALP obtained by the Canadian Laboratory Initiative in Pediatric Reference Intervals (CALIPER) in children and adolescents, adjusted for the Brazilian population. Methods: The ALP measures from 1690 subjects (aging from 1-18 years) were analyzed. The CALIPER subgroups and the Clinical and Laboratory Standards Institute (CLSI) guideline were used for validation. Inclusion criteria were patients with normal range of hepatic and renal function, bone metabolism, and blood counts. Exclusion criteria were hospitalization, low weight, and use of drugs that could interfere in the ALP measurement and patients in with more than three orders for ALP measuring test. The RI obtained were considered valid if more than 90% of patients were whitin of the CALIPER RI. Results: The ALP RI results (IU/l) obtained were: 149-301 for both sexes aged 1-9 years; 127-326 for both sexes aged 10-12 years; 62-212 for girls and 129-437 for boys aged 13-14 years; 52-120 for girls and 78-268 for boys aged 15-16 years; 45-97 for girls and 40-129 for boys aged 17-18 years. In 92.4% of the patients, the results were comparable with those of the CALIPER study. Conclusion: The results demonstrated that the ALP RI for Brazilian children and adolescents are comparable to the CALIPER study in 92.4% of the patients and can be used for this population.