Intralaboratory survey of alkaline phosphatase methods.

Three sets of interrelated specimens containing alkaline phosphatase (ALP) were analyzed: CAP 1977 Enzyme Survey serum, human serum supplemental with calf intestinal ALP, and human serum with increased human liver ALP. Five quite distinct ALP methods were used. In addition, fresh serum from volunteer blood donors and serum from patients with increased serum ALP activities were examined by each of these five methods. Conversion factors for the five different methods based on results from calf-intestine-supplemented interrelated specimens could not be used to interconvert results for fresh human serum. However, the interrelated specimens with increased human liver ALP made interconversion of results for fresh human serum possible.