[A macromolecule capable of modifying CK-MB results and of inducing false acute myocardial infarction diagnosis].

Purpose: To evaluate the diagnostic value of CK-MB in acute myocardial infarction, to differentiate the relation between creatine phosphokinase (CPK), CK-MB and macro CK-BB (a macromolecule formed by an atypic CK-BB linked to an immunoglobulin) and to investigate the association of macro-BB with cancer.

Methods: We studied 105 patients: 47 with various tumors; 8 with acute myocardial infarction and one control group with 50 persons without cardiac or oncologyc diseases. The CK-MB, CPK and macro CK-BB were measured in the serum of all patients and of the control group.

Results: Among patients with cancer, 12 (25.6%) showed positive serum macro CK-MB. Two of them (16.6%) showed concomitant increase in CK-MB. All patients with increased serum macro CK-MB had malignant tumors.

Conclusion: The CK-MB is a reliable test for the myocardial infarction, however, when this isozyme is increased in the presence of normal CPK value, it must be questioned the presence of macro CK-BB to avoid false positive results. The presence of macro CK-BB could be relationed with malignant disease, specially with carcinoma of the prostate.