Does determination of serum aspartate aminotransferase contribute to the diagnosis of acute myocardial infarction?

Values for total lactate dehydrogenase (LD), LD isoenzymes, and serum aspartate aminotransferase (AST) were determined in 150 patients with acute myocardial infarction (AMI) and 130 non-AMI patients 24, 48, and 72 hours after admission. The authors assessed the diagnostic yield of a single determination of AST, LD, and three LD isoenzymes tests: LD-1 greater than LD-2; LD-1 greater than 90 U/L; LD-1/LD greater than 0.4. They also assessed the diagnostic accuracy of combined determination of AST with LD and AST with each of the above three LD isoenzymes tests. The efficiency of single determination of AST was better than that of LD (88% vs. 80%, 48 hours after admission). The most efficient single test for diagnosing AMI was the LD-1 greater than 90 U/L test (92%, 48 hours after admission). The efficiency of the combined AST/LD test was better than that of a single determination of each of the two enzymes (90% vs. 88% and 80%, 48 hours after admission). The highest efficiency was achieved, however, with combined determination of AST and any of the three LD isoenzymes tests. It was found to be more efficient than single determination of each of the LD isoenzymes tests (95.5-96% vs. 89-92.5%) and more efficient than the combined determination of the AST/LD test (95.5-96% vs. 89-90%). The authors conclude that AST should be determined in every patient with suspected AMI because its determination may contribute to the diagnostic yield of LD isoenzymes tests, especially in patients with AMI admitted 48-72 hours after onset of symptoms, when creatine kinase declined to near normal values.