Determination of serum alkaline phosphatase reference in healthy children aged 1-18 years

The growth and development of children affect biochemical variables. This population-based study was designed to evaluate the reference interval for alkaline phosphatase (ALP) routinely measured in the clinical laboratory.

For this examination, 873 cases were selected among the healthy children and adolescents aged 1-18 years who referred to the endocrinology clinic of Amirkola Children's Hospital for growth evaluation. After overnight fasting, early morning blood samples were obtained to measure the ALP level and other biochemical parameters using an automatic biochemical analyzer. Subjects were categorized by age, sex, and body mass index (BMI) values. The age groups were categorized as follows: 1-4 years, 5-8 years, 9-13 years, and 14-18 years.

There was a significant difference among the age and sex categories; on the contrary, there was no meaningful variation between the two groups categorized by BMI. The reference range for ALP was 474.14-517.71 U/L for children aged 1-4 years, 273.47-871.44 U/L for 5-8 years, 215.04-893.69 U/L for 9-13 years, and 228.9-739.22 U/L for 14-18 years. Also, significant positive correlation was found between ALP with length (P=0.000, r=0.134), weight (=0.04, r=0.073), phosphorus (P) (P=0.001, r=0.122), and alanine aminotransferase (SGPT) (P=0.000, r=0.142) respectively.

This project's data established a reference interval for ALP in healthy children and adolescents, which will prepare a basis for diagnosis and monitoring liver- or bone-related disorders.