title: Creatine kinase-MB mass concentration versus creatine kinase-B activity for the detection of acute myocardial infarction in patients with slightly elevated total creatine kinase activity in serum.
abstract: OBJECTIVE
  The diagnostic value of creatine kinase-MB mass concentration (CK-MB mass) was compared with that of creatine kinase-B (CK-B) activity in patients with suspected acute myocardial infarction (AMI) but with total serum CK activity only slightly above the reference range.
  
  
  METHODS
  One hundred consecutive blood samples with total CK activity between 120 and 360 U l-1 and CK-B activity > or = 9 U l-1 were analysed. Electrophoresis of CK isoenzymes was also performed.
  
  
  METHODS
  Patients from all departments of the hospital were included. About half of the patients originated from the coronary care unit.
  
  
  METHODS
  The blood samples derived from 49 patients. Thirteen patients had at least one serum sample with total CK activity above 360 U l-1. These and another three patients were omitted from the study.
  
  
  RESULTS
  Acute myocardial infarction had been diagnosed clinically (with CK and CK-B methods) in 12 of 33 patients. However, using the CK-MB mass concentration of the reference method, five of these 12 patients did not have myocardial infarction whereas nine patients with small infarctions were undetected. A good correlation was seen between the results from CK-MB mass concentration and CK isoenzyme electrophoresis, but there was a poor correlation between these methods and CK-B activity including the CK-B/CK ratio. A relatively high proportion (24%) of the selected patients had increased levels of macro CK.
  
  
  CONCLUSIONS
  CK-B activity was inaccurate for the detection of probably myocardial infarction in patients with slightly elevated total CK activity. Increased levels of macro CK interfering with the CK-B assay was one explanation for this observation.
authors.affiliation: Department of Cardiology, Karolinska Institute at Södersjukhuset, Stockholm, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Hulting
authors.forename: L
authors.initials: L
authors.lastname: Waldenlind
authors.forename: D
authors.initials: D
authors.lastname: Onica
authors.forename: H
authors.initials: H
authors.lastname: Wallinder
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D004796:Clinical Enzyme Tests; D003402:Creatine Kinase / Q000097:blood*; D005260:Female; D006801:Humans; D007527:Isoenzymes; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis*; D013053:Spectrophotometry
chemical_list: D007527:Isoenzymes; D003402:Creatine Kinase