Higher Levels of Creatine Kinase MB (CK-MB) Than Total Creatine Kinase (CK): A Biochemistry Reporting Error or an Indicator of Other Pathologies?

The creatine kinase (CK) enzyme and its isoenzymes hold significant diagnostic value, appearing in distinct patterns across various tissues. The most common method for creatine kinase MB (CK-MB) estimation is based on immunoinhibition. However, this method can report falsely elevated CK-MB levels in various scenarios. Persistently elevated CK-MB levels or discrepancies between measured values and the patient's clinical condition warrant further investigation, such as total CK isoenzyme electrophoresis. This report presents a case where a patient was diagnosed with acute myocardial infarction and treated according to established guidelines. However, the presence of abdominal pain, in addition to persistently elevated CK-MB after the resolution of cardiac symptoms and a higher CK-MB to total CK ratio, suggested alternative pathologies. Thorough laboratory investigations, including quantitative CK isoenzyme electrophoresis and contrast-enhanced computed tomography (CECT) of the abdomen, followed by emergency operative intervention, led to a secondary diagnosis of acute small bowel infarction.