Evaluation of a method for measuring tissue non-specific alkaline phosphatase activity in healthy subjects

Abstract

Intestinal alkaline phosphatase (IAP) isozymes in the healthy human serum samples appears in two isoforms: normal-molecular-weight IAP (NIAP) and high-molecular-weight IAP (HIAP). We have demonstrated that the reference range for serum alkaline phosphatase (ALP) activity is higher in blood group B and O antigen secretors than in the tested other blood groups, for the appearance of these isoforms is depended on blood group B or O antigen secretors. We assessed a diethanolamine-L-phenylalanine (DEA-Phe) method for measuring tissue non-specific alkaline phosphatase (TNAP). This assays the sum of liver alkaline phosphatase and bone alkaline phosphatase activities as determined by an inhibiting IAP activity method with Phe. We classified 420 healthy subjects into two groups, a group of subjects who had blood group B or O antigen secretors (n = 184) and a group of subjects who had other blood groups (n = 236). ALP activity was higher in the B or O secretor group than in the other group: 20.9% higher (P<0.001) by the N-methyl-D-glucamine method, 13.7% higher (P<0.002) by 2-amino-2-methyl-1-propanol method, and 9.6% higher (P<0.05) by the diethanolamine method, but there was no significant difference in TNAP activity between the two blood group when measured by the DEA-Phe method. These results of this study support the expectation that the DEA-Phe method would be specific for TNAP activity. In addition, the reference range for TNAP activity did not vary with the differences in the tested all blood groups.