To the Editor.
—In a report1 published in THE JOURNAL, a patient was described who had adenocarcinoma of the lung with an elevated serum level of what at first appeared to be the MB isoenzyme of creatine kinase (CK), but was found not to be "true" MB. Subsequently, in the LETTERS section of THE JOURNAL, the true nature of the CK-MB reported by these authors, and also by previous workers, was discussed.2 A small number of patients with cancer who had elevated serum levels of CK-MB have previously been reported. In only one case3 was the isoenzyme identified in tumor tissue. Unfortunately, the primary means of identification in all of these reports was electrophoresis. While electrophoresis is an important component of such identification, it is not diagnostic by itself. Non-MB isoenzymes migrating as CK-MB have been reported in the literature and we have also identified such a
McGing PG, Kyne F, Johnston P, Carney DN. Elevation of True Creatine Kinase—MB in a Patient With Small-Cell Lung Cancer. JAMA. 1988;259(6):844. doi:10.1001/jama.1988.03720060016023