Emergency serum creatine kinase MB isoenzyme concentration in patients with suspected acute myocardial infarction.

We report the results of the introduction of a service which offered emergency measurement of serum creatine kinase MB isoenzyme concentration in patients admitted to hospital with suspected acute myocardial infarction and a non-diagnostic electrocardiogram. A retrospective study suggested that in such patients, a single admission measurement would have a diagnostic sensitivity of 70% and specificity of 100%. A prospective study employed a protocol which included repeat measurement after two hours where the initial measurement was low in samples taken less than six hours after the onset of symptoms. The prospective study showed that the service was welcomed by physicians, who employed the measurements appropriately as a supplement to, rather than substitute for, clinical judgement. In a continuing audit, 228 patients had an emergency measurement according to the agreed protocol. 79 of these had a discharge diagnosis of acute myocardial infarction. The diagnostic sensitivity and specificity of our emergency strategy were both 94%. The strategy led to the treatment with thrombolytic drugs of 73 patients who would not otherwise have been treated, 69 with a discharge diagnosis of acute myocardial infarction, and four with some other discharge diagnosis. The median time taken from requesting the analysis to reporting the result was 34 minutes. The costs and potential benefits of our strategy are discussed.