Small increases of the serum alkaline phosphatase activity and malignant changes

In order to see the clinico-pathological significance of the small increase of serum alkaline phosphatase (ALP) activity alone in routine laboratory examinations, we picked up 76 new out-patients of adult within the two-fold high ALP level in contrast to the reference range in the Akita University Hospital for one year, and then studied the relation between the histories and serum ALPs of 33 patients whose ALP had increased pathologically or decreased after intervention such as surgical operations. The ratio of the patients with malignant tumors to the tested all patients was 13 to 76 (17%). Immunochemical analysis of sera for the cancers of the lung, larynx and prostate showed that the small amount of the placental isozyme or intestinal-like isozyme was expressed selectively. It may be useful for earlier detection of malignancy to analyze the cancer-associated ALPs, when the small and sequential increase of the serum ALP activity is found in routine laboratory examinations.