Clinical significance of a low serum alkaline phosphatase

The reasons for a low serum alkaline phosphatase activity were reviewed in a 1-yr retrospective study of all the results emanating from a central, university hospital laboratory. Apart from occasional errors, hypophosphatasaemia was encountered in neonates undergoing exchange transfusions with plasma, in patients (particularly children) receiving chemotherapy and during cardio-pulmonary bypass. Low activity values were recorded in several individuals in the absence of any obvious cause. This would suggest that the definition of the lower limit of the reference range for alkaline phosphatase is arbitrary, thus limiting the use of low serum activity as a marker of disease.