Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

The significance of elevated levels of the MB isomer of creatine kinase (CK-MB) when creatine kinase (CK) level is normal was studied in 400 patients with suspected acute myocardial infarction (AMI). In 350 patients both CK and CK-MB were elevated (group 1), in 21 only CK-MB was elevated (group 2), in 24 neither enzyme was elevated (group 3) and in 5 only CK was elevated (group 4). In 57% of patients in group 2 the CK level was doubled, with a characteristic enzyme curve, within the normal range, suggesting that an increase in CK had been missed because arbitrary definitions of 'normal' were used. The median CK increase (60 IU/liter) in group 2 was greater than that in group 3 (23 IU/liter) (p < 0.001). Patients in group 1 with small AMIs had a relative increase in CK similar to that in group 2. However, patients in group 2 had a lower baseline CK level so that peak CK did not become abnormally high despite a 5-fold increase in some patients. In patients in group 1 with small AMIs, CK was elevated in fewer samples than CK-MB. If only 2 samples were obtained in all patients, elevation of CK levels would have been missed in 63 group 1 patients, erroneously increasing the number of patients in group 2 fourfold (to 84 of 400, or 21%, instead of 21 of 400, or only 5%). Conversely, if patients in group 2 with a doubling of CK are excluded, the prevalence of elevated CK-MB with normal CK would be only 9 of 400 (2%). The proportion of patients in group 2 with independent markers of AMI was intermediate between group 1 and group 3. Four-year follow-up suggested a good prognosis in group 2 patients.

Original publication




Journal article


American Journal of Cardiology

Publication Date





245 - 250