Serum Enzyme Assays in the Diagnosis of Acute Myocardial Infarction Recommendations Based on a Quantitative Analysis

doi:10.1059/0003-4819-105-2-221

Serum Enzyme Assays in the Diagnosis of Acute Myocardial Infarction Recommendations Based on a Quantitative Analysis

THOMAS H. LEE, M.D.; and
LEE GOLDMAN, M.D., M.P.H.

Boston, Massachusetts

Abstract

In the last 20 years, serum enzyme and isoenzyme levels have become the final arbiters by which acute myocardial infarction is diagnosed or excluded. We review the characteristics of these enzymes, the methods and limitations of commonly used assays, and data on diagnostic accuracy and clinical implications of enzyme levels in various settings and offer recommendations on their optimal use. Because of the poor sensitivity of single measurements of cardiac enzyme levels, these assays should not be used in the emergency room to exclude myocardial infarction. If myocardial infarction is suspected, levels of creatine kinase and its MB fraction should be measured at admission and about 12 and 24 hours later. If a myocardial infarction may have occurred more than 24 hours before evaluation, then lactate dehydrogenase isoenzyme measurements may increase diagnostic accuracy. Used properly, these assays are remarkably sensitive, but like all tests, optimal interpretation requires insight into technical pitfalls and other causes of misleading results.

Article and Author Information

▸From the Cardiovascular Division and the Division of General Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School; Boston, Massachusetts.
▸This paper was commissioned by the Blue Cross-Blue Shield Medical Necessity Project, under auspices of the Society for Research and Education in Primary Care Internal Medicine (SREPCIM), and is the seventh in a series being published in the Diagnosis and Treatment section. Harold C. Sox, Jr., M.D., is the editor for the series, and these papers are also being reviewed by John M. Eisenberg, M.D., and Sankey V. Williams, M.D., our consultants for Diagnostic Decision papers, as well as by selected manuscript consultants. This series will be published in a collective reprint, the availability of which will be announced later. The reprint will include the introductory article by Dr. Sox, which appears on pages 60-66 in the January issue.—The Editor.
▸Requests for reprints should be addressed to Lee Goldman, M.D., M.P.H.; Department of Medicine, Brigham and Women's Hospital, 75 Francis Street; Boston, MA 02115.