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Alkaline phosphatase in healthy children: reference intervals and prevalence of elevated levels
Peter Ridefelt1, Jan Gustafsson, Mattias Aldrimer
1Department of Medical Sciences, Clinical Chemistry, Uppsala University, Uppsala, Sweden.
Insights
Transient hyperphosphatasemia (TH) is a benign condition affecting young children. This study found a prevalence of 6.2% for high alkaline phosphatase (ALP) in healthy children under two years old.
Area of Science:
- Pediatric Endocrinology
- Clinical Chemistry
Background:
- Transient hyperphosphatasemia (TH) is a benign condition often affecting children under 5.
- The prevalence of high alkaline phosphatase (ALP) in healthy children is largely unknown.
- This study aimed to estimate TH prevalence and establish pediatric reference intervals for ALP.
Purpose of the Study:
- To estimate the prevalence of high alkaline phosphatase (ALP) in healthy children.
- To calculate age- and gender-specific pediatric reference intervals for ALP.
- To investigate the characteristics of children with elevated ALP levels.
Main Methods:
- Blood samples were collected from 699 healthy children aged 6 months to 18 years.
- Children with high ALP levels were identified and excluded for reference interval calculation.
- Prevalence was calculated for specific age groups.
Main Results:
- Six children (6.2%) aged 7-22 months had ALP levels >16.7 µkat/l.
- No older children exhibited ALP levels above this threshold.
- While TH was suspected, other causes for elevated ALP could not be excluded, though general chemistry analyses were normal.
Conclusions:
- The prevalence of high ALP in healthy children is approximately 2.4% under 5 years and 6.2% under 2 years.
- Pediatric reference intervals for ALP are dependent on age and gender.
- Further follow-up is needed to confirm TH in children with elevated ALP.
Background:
Transient hyperphosphatasemia (TH) is an often unnoticed benign entity, primarily affecting children below 5 years of age. However, the prevalence among healthy children is unknown. We used data from a Swedish pediatric reference interval project to estimate the prevalence of high alkaline phosphatase (ALP) among healthy children and to calculate pediatric reference intervals.
Methods:
Blood was collected from 699 subjectively healthy children aged 6 months to 18 years. After exclusion of subjects with high ALP, age- and gender-specific reference intervals were calculated.
Results:
Six children had ALP levels >16.7 µkat/l (>1,000 U/l), including 4 females and 2 males aged 7-22 months. The prevalence in the age group from 6 months to 2 years was 6.2% (6/97). None of the older children had levels of ALP >16.7 µkat/l. The study did not include the follow-up of these apparently healthy children. Consequently, conditions others than TH explaining the elevated ALP could not be excluded. However, general chemistry analyses, such as liver enzymes, calcium, intact PTH and vitamin D, were essentially normal in these children.
Conclusions:
The prevalence of high ALP among subjectively healthy children was approximately 2.4% below 5 years of age and 6.2% below 2 years. Reference intervals vary with age and gender.
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