Immunological determination of muscle-type enolase in the serum as a diagnostic test for myocardial infarction.

An antiserum raised in the chicken against purified rat skeletal muscle enolase neutralized 86% of the enolase activity of human heart muscle and 8.7% +/- 4.8% (mean +/- S.D.) of the enolase activity in normal human serum. The fraction of enolase inhibited by the antiserum, designated as 'immunologically reacting muscle enolase', promptly rose after myocardial infarction in the serum of affected subjects, reaching peak values in excess of 40% in all but one of 23 subjects. Only one subject with ischaemic heart disease, but without infarction, and 2 with miscellaneous conditions, among 117 such patients tested, yielded comparable values. The test appears to be highly specific for myocardial infarction when muscle disease can be excluded and would not be difficult to introduce as a laboratory routine.