Serial measurements of serum creatine kinase are of most use in the exclusion of acute myocardial infarction in patients with a history of heart disease.

Rapid sequential measurements of serum CK were assessed in the diagnosis and exclusion of acute myocardial infarction (MI) in 94 patients presenting to St Thomas' Hospital, London, with acute chest pain of less than 12 h duration. A blood sample was taken from patients on admission to hospital and then a second sample was taken within 12 h of admission. Serum CK activity was assayed on both samples and delta log10 (serum CK) per hour calculated to distinguish infarct from non-infarct using a discriminant value of 0.015. Ninety-six per cent of patients with acute MI were diagnosed on the basis of clinical history and electrocardiographic evidence alone, and did not require biochemical confirmation. Serial estimation of serum CK contributed positively towards the exclusion of acute MI in 77% of patients who presented with chest pain and who had a previous history of heart disease, but towards only 11% of cases in the absence of a history of heart disease.