title: Use of creatine kinase MB isoenzyme for diagnosing myocardial infarction when total creatine kinase activity is high.
abstract: The usefulness of measuring creatine kinase MB isoenzyme for diagnosing myocardial infarction when activities of total creatine kinase are very high is unclear. We conducted a retrospective study in an urban hospital that serves a largely indigent population. We concentrated on 146 patients whose creatine kinase activity was greater than 1000 U/L (upper limit of normal: 165 U/L for women and 225 U/L for men), with MB isoenzyme greater than 10 U/L and less than 5% of total creatine kinase. The positive predictive value of MB isoenzyme (isoimmune method) values greater than 10 U/L was between 11.6% and 56.8% when the value for total creatine kinase exceeded 1000 U/L. Using different values (MB greater than 4% of total creatine kinase) as positive for myocardial infarction would have resulted in far fewer false-positives, but 10 cases of myocardial infarction would have been missed. The most appropriate cutoff value for MB isoenzyme in this population (total creatine kinase greater than 1000 U/L) was found to be greater than 2% of total creatine kinase.
authors.affiliation: Department of Medicine, New York University School of Medicine, NY 10016.
authors.forename: W G
authors.initials: WG
authors.lastname: Thompson
authors.forename: R G
authors.initials: RG
authors.lastname: Mahr
authors.forename: W S
authors.initials: WS
authors.lastname: Yohannan
authors.forename: M R
authors.initials: MR
authors.lastname: Pincus
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D003042:Cocaine; D003402:Creatine Kinase / Q000097:blood*; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D007527:Isoenzymes; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis*; D012189:Retrospective Studies; D019966:Substance-Related Disorders
chemical_list: D007527:Isoenzymes; D003402:Creatine Kinase; D003042:Cocaine