Alkaline phosphatase in paediatric practice: a practical approach with a proposed diagnostic algorithm

This review summarises the clinical relevance of alkaline phosphatase (ALP) in paediatrics, placing emphasis on its biochemical heterogeneity, age-dependent physiology and diagnostic value in bone and hepatobiliary disorders. ALP is a group of membrane-bound enzymes, predominantly represented in serum by tissue-nonspecific alkaline phosphatase, with major contributions from bones and the liver. In children, interpretation of ALP concentration is complicated due to marked physiological variation occurring in growth and puberty, as well as by method-dependent differences in laboratory reference ranges. An elevated ALP activity may reflect normal growth; however, it may also result from benign transient hyperphosphatasaemia, rickets, fibrous dysplasia, juvenile Paget's disease, metabolic bone disease of prematurity or cholestatic liver disease. Low ALP activity, although less common, may be associated with hypophosphatasia, malnutrition, micronutrient deficiencies or medication effects. ALP should, therefore, be interpreted in the context of age, clinical presentation and supplementary findings of biochemical tests and diagnostic imaging.