Alkaline phosphatase isoenzymes for the diagnosis of metastatic tumors and lymphomas of liver and bone.

The plasmatic activities of total alkaline phosphatase (ALP) (E.C. 3.1.3.1), high molecular weight-ALP (high Mr-ALP) and bone-ALP isoenzymes, were determined in healthy individuals and in patients with: neoplasia without metastases, hepatic metastases, bone metastases and mixed metastases (hepatic and bone). Variables were individually used to assess incidence of metastases and percentages of false negative and false positive results were calculated. The three values were then used together to assess metastases incidence and sensitivity, specificity, positive predictive value, negative predictive value and predictive capacity were estimated. We conclude that none of the variables per se are reliable for the diagnosis of metastases. On the other hand, the three values show high percentages of sensitivity, specificity, positive predictive value, negative predictive value and a high probability (0.93) of accurate diagnosis when applied to a larger population, with similar prevalence values.