Clinical Chemistry, Vol 34, 2506-2510, Copyright © 1988 by American Association for Clinical Chemistry

Creatine kinase:aspartate aminotransferase activity ratio as an indicator of the source of an increased creatine kinase activity

DR Dufour
Laboratory Service, Veteran's Administration Medical Center, Washington, DC 20422.

Although measurements of creatine kinase isoenzyme 2 (CK-MB) are often used to diagnose acute myocardial infarction, their sensitivity and specificity are less than 100%. Because skeletal muscle contains more CK and less aspartate aminotransferase (AST) than cardiac muscle, the CK/AST ratio might provide a useful adjunct in evaluating the source of a supranormal value for CK. I established the following decision levels in a retrospective study of 342 patients: ratios less than 14 (if total CK was 300-1200 U/L), less than 20 (CK 1201-2000 U/L), or less than 25 (CK greater than 2000 U/L) suggested myocardial infarction, with a sensitivity of 95% and a specificity of 65%. In a validation study with 277 additional patients, liver disease and alcohol abuse caused erroneous results, leading to exclusion of 22% of these patients. In the remaining cases, sensitivity was 94%, specificity 90%. The CK/AST ratios changed little with time, suggesting that a single value would be adequate for evaluating patients with increased CK.

The following articles in journals at HighWire Press have cited this article:

				A. Larsson, N. Tryding, and D. R. Dufour Is It Necessary to Order Aspartate Aminotransferase with Alanine Aminotransferase in Clinical Practice? Dr. Dufour responds: Clin. Chem., June 1, 2001; 47(6): 1133 - 1135. [Full Text] [PDF]