Biological and pathological factors affecting plasma gamma-glutamyl transpeptidase and alkaline phosphatase activity in the elderly.

A high percentage of abnormally elevated plasma alkaline phosphatase (AP) and gamma-glutamyltranspeptidase (GGT) was found in a homogeneous population of 741 elderly subjects. The respective role of pathological and biological factors (age, sex, weight) upon the two plasma enzymatic activities has been analyzed. In disagreement with previous reports, it was observed that abnormal AP and GGT values could be readily explained by their association with specific diseases. The apparent relationship between abnormal levels of plasma AP and GGT activities and age, sex or weight reflected merely a different distribution of the pathology according to these biological parameters. In the absence of non-specific elevations of plasma AP and GGT activities with age, the usual reference values for these tests, although established on younger populations, still apply to the aged.