Ectopic Production of Creatine Kinase MB: Updated Evaluation by Mass

There have been several reports of apparently high concentrations of creatine kinase (CK)-MB in the sera of cancer patients [1–4]. In several of these cases, the high activity resulted from the presence of macro CK types 1 and 2 [5]. False-positive results for CK-MB can occur if nonspecific as-says such as immunoinhibition are used [6]. These atypical isoenzymes are not inhibited by anti-CK-B anti-bodies, and high apparent CK-MB activities are produced. Macro CK type 1 (CK-BB bound to IgG) mi-grates between CK-MM and-MB