title: Early diagnostic efficiency of cardiac troponin I and Troponin T for acute myocardial infarction.
abstract: OBJECTIVE
  To compare the early diagnostic efficiency of the cardiac troponin I (cTn-I) level with that of the cardiac troponin T (cTn-T) level, as well as the creatine kinase (CK), CK-MB, and myoglobin levels, for acute myocardial infarction (AMI) in patients without an initially diagnostic ECG presenting to the ED within 24 hours of the onset of their symptoms.
  
  
  METHODS
  A prospective, observational, cohort study was performed involving chest pain patients admitted to a large urban community hospital. Participants were consecutive consenting ED chest pain patients > or = 30 years of age. Exclusions included duration of symptoms > 24 hours, inability to complete data collection, receipt of CPR, and ST-segment elevation on the initial ECG. Measurements included levels of cTn-I, cTn-T, CK, CK-MB, and myoglobin at the time of presentation and 1, 2, 6, and 12-24 hours after presentation as well as presenting ECG and clinical follow-up. Confirmation of the diagnosis of AMI was based on World Health Organization criteria.
  
  
  RESULTS
  Of the 177 patients included in the study, 27 (15%) were diagnosed as having AMIs. The sensitivities of all 5 biochemical markers for AMI were poor at the time of ED presentation (3.7-33.3%) but rose significantly over the study period. The sensitivity of cTn-T was significantly better than that of cTn-I over the initial 2 hours, but both markers' sensitivities were low (< 60%) during this time frame. The cTn-I was significantly more specific for AMI than was the cTn-T, but not significantly better than CK-MB or myoglobin. Likelihood ratio analysis showed that the biochemical markers with the highest positive likelihood ratios for AMI during the first 2 hours following ED presentation were myoglobin and CK-MB. From 6 through 24 hours, the positive likelihood ratios for cTn-I, CK-MB, and myoglobin were superior to those of CK and cTn-T.
  
  
  CONCLUSIONS
  cTn-I, CK-MB, and myoglobin are significantly more specific for AMI than are CK and cTn-T. Myoglobin is the biochemical marker having the highest combination of sensitivity, specificity, and negative predictive value for AMI within 2 hours of ED presentation. Neither cTn-I nor cTn-T offers significant advantages over myoglobin and CK-MB in the early (< or = 2 hours) initial screening for AMI. The cardiac troponins are of benefit in identifying AMI > or = 6 hours after presentation.
authors.affiliation: Department of Emergency Medicine, St Luke's Medical Center, Milwaukee, WI 53215, USA.
authors.forename: J F
authors.initials: JF
authors.lastname: Tucker
authors.forename: R A
authors.initials: RA
authors.lastname: Collins
authors.forename: A J
authors.initials: AJ
authors.lastname: Anderson
authors.forename: J
authors.initials: J
authors.lastname: Hauser
authors.forename: J
authors.initials: J
authors.lastname: Kalas
authors.forename: F S
authors.initials: FS
authors.lastname: Apple
mesh_terms: D015415:Biomarkers / Q000097:blood*; D006801:Humans; D009203:Myocardial Infarction / Q000097:blood*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D013997:Time Factors; D014336:Troponin / Q000097:blood*; D019210:Troponin I / Q000097:blood*; D020107:Troponin T
chemical_list: D015415:Biomarkers; D014336:Troponin; D019210:Troponin I; D020107:Troponin T