RESUMO
The cardiospecific isoenzyme MB of creatine kinase (CKMB) has previously been shown to be of value in the diagnosis of myocardial infarction (MI). We studied 418 admissions to a coronary care unit (CCU) with suspected MI and calculated the sensitivity, specificity and positive and negative predictive values for several CKMB test functions. Several functions performed better than any combination of the other enzymes in common use. 97% of patients achieving a CKMB activity of at least 15 U/l did so between 6 and 30 h following the onset of symptoms. The present study confirms that the use of the CKMB isoenzyme leads to an earlier and more accurate diagnosis or exclusion of MI compared to the "cardiac enzyme series". The timing of blood sampling for CKMB estimation is also discussed.