Abstract
The factors which affect the standardisation and quality control of serum alkaline phosphatase assays are discussed. A quality control project was designed to test the performance of seven Birmingham laboratories in the assay of sera with alkaline phosphatase activities outside the range normally tested by the National Quality Control and Wellcome schemes. The results showed that the precision of individual laboratories was satisfactory. Differences between the results of the laboratories were considerable and could be accounted for by differences in methodology. AutoAnalyzer methods employing phenyl phosphate as substrate would best be standardised by adopting the optimised reaction conditions of Buch and Buch (1939); but the borate buffer of these authors should be replaced by the carbonate-bicarbonate buffer of Moss et al. (1971). To avoid the confusion which may arise in future if alkaline phosphatases are reported in U/1 irrespective of the substrate, it is suggested that some substrate—indicative nomenclature may be advisable.