Transient Hyperphosphatasaemia of Infancy: An Often Unrecognised and Thus Over-Investigated Condition

Transient hyperphosphatasaemia of infancy (THI) is a benign condition characterised by a rapid rise and fall in plasma alkaline phosphatase (ALP) activity without biochemical or clinical evidence of underlying bone or liver disease. It is most often identified incidentally during routine blood testing; hence it is important to recognise this phenomenon in order to avoid unnecessary investigations and inappropriate referrals. This review has provided some useful insight into the characteristics associated with the THI and the routine clinical practice when isolated elevation of plasma ALP is found in patients at two sites in Republic of Ireland. Over a period of two years, 107,468 requests for plasma ALP analysis were received, of which a total of 250 patients were identified with a plasma ALP activity above 1000IU/L. The biochemical diagnosis of THI was considered in 62 patients, 15 (25%) of these were inappropriately investigated and 5 (13%) were unnecessarily referred to tertiary care by their general practitioners. We recommend that if an isolated high plasma ALP activity is detected during routine blood testing without any indication of bone or liver disease, it is important to consider THI in the differential diagnosis and to repeat the plasma ALP in 7-10 days. This should be further confirmed by the normalisation of the plasma ALP activity in 2-3 months or by ALP isoenzyme analysis where deemed appropriate by the laboratory.