Impact of the troponin standard on the prevalence of acute myocardial infarction.
BACKGROUND
Recent recommendations are that troponin should replace creatine kinase (CK)-MB as the diagnostic standard for myocardial infarction (MI). The impact of this change has not been well described. Our objective was to determine the impact of a troponin standard on the prevalence of acute non-ST-elevation MI.


METHODS
The current study was a retrospective analysis of consecutive patients without ST-segment elevation admitted for exclusion of myocardial ischemia to an inner city urban tertiary care center. All patients underwent serial marker sampling (CK, CK-MB, and cardiac troponin I [cTnI]). Patients with ST elevation consistent with acute MI (n = 130) or who did not have an 8 hour cTnI (n = 124) were excluded. The impact of 3 different cTnI diagnostic values were examined in 2181 patients: the lower limit of detectability (LLD); an optimal diagnostic value (OPT), chosen using receiver operator characteristic curve analysis; and the manufacturer's suggested upper reference level (URL), when compared to a gold standard CK-MB MI definition. In addition, MI prevalence was assessed using different CK-MB MI definitions and evaluated in patients with ischemic changes only.


RESULTS
The prevalence CK-MB MI was 7.8%. Using the various cTnI diagnostic values, the incidence of MI increased the prevalence by 28% to 195%. Using the optimal diagnostic value for cTnI, patients with cTnI elevations not meeting CK-MB MI criteria had an intermediate 30-day mortality (5.4%) compared to those with CK-MB MI (7.1%). Grouping the cTnI positive, CK-MB MI negative patients with the CK-MB MI patients rather than the non-CK-MB MI patients reduced mortality for both the MI (to 5.9%) and non-MI groups (from 1.9% to 1.6%).


CONCLUSIONS
Changing to a troponin standard will have a substantial impact on the number of patients diagnosed with MI. The revised definition for MI will have important clinical and health care implications.
Kontos
Michael C
MC
Department of Internal Medicine, Cardiology Division, Medical College of Virginia, Virginia Commonwealth University, Richmond, Va 23298-0051, USA. mkontos@hsc.vcu.edu
Fritz
Lucie M
LM
Anderson
F Philip
FP
Tatum
James L
JL
Ornato
Joseph P
JP
Jesse
Robert L
RL
D000368:Aged; D015415:Biomarkers / Q000097:blood; D002637:Chest Pain; D003402:Creatine Kinase / Q000097:blood*; D052279:Creatine Kinase, MB Form; D004562:Electrocardiography; D005260:Female; D006801:Humans; D007527:Isoenzymes / Q000097:blood*; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology; D017202:Myocardial Ischemia / Q000097:blood / Q000175:diagnosis; D015995:Prevalence; D012372:ROC Curve; D012016:Reference Values; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D019210:Troponin I / Q000097:blood*; D020107:Troponin T / Q000097:blood
D015415:Biomarkers; D007527:Isoenzymes; D019210:Troponin I; D020107:Troponin T; D003402:Creatine Kinase; D052279:Creatine Kinase, MB Form