To the Editor.
—We read with interest the study by Fisher et al,1 published in the August 1983 Archives, on the use of enzyme measurements for the diagnosis of acute myocardial infarction (MI). They demonstrated clearly that total serum creatine kinase (CK) and CK isozyme measurements are sufficient in determining acute MI, and that additional enzymatic assays should only be done when the CK results have been equivocal. We would like to point out, however, that their conclusions have been reached in a hospital in which CK isozyme assays are done accurately by a method differ ent from the immunoinhibition method used in many places. The immunoinhibition method uses blocking antibodies, which selectively inhibit the activity of the CK-M subunit in CK-MM and in CK-MB, and only the enzymatic activity of the B part of the CK-MB and CK-BB is left intact.2 Since most of the CK-BB activity