Elsevier

American Heart Journal

Volume 146, Issue 3, September 2003, Pages 446-452
American Heart Journal

Clinical investigations
Impact of the troponin standard on the prevalence of acute myocardial infarction

Presented in part in at the Sessions of the American Heart Association Scientific Meetings, November 2001, Anaheim, Calif.
https://doi.org/10.1016/S0002-8703(03)00245-XGet rights and content

Abstract

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.

Section snippets

Methods

This study was performed at a 600-bed inner city hospital with approximately 85,000 ED visits a year. Approximately 2900 patients a year undergo an ED evaluation for ischemia, and of these, 1545 are admitted to the coronary care unit (CCU). The chest pain protocol used at our institution has been described in detail previously.9 After the initial evaluation, patients thought to be at high risk (those with ischemic echocardiographic [ECG] changes or with known coronary disease and typical

Results

Patient characteristics and demographic variables of the 2181 patients are shown in Table I. CK-MB MI was present in 170 patients (7.8%). The area under the ROC curve was 0.971 ± 0.005, indicating a high diagnostic test performance. The optimal diagnostic value, which increased specificity without significantly decreasing sensitivity, was 0.3 ng/mL. Using these diagnostic values, 152 patients (7.0%) had cTnI values between the LLD and the optimal diagnostic value; 115 patients (5.3%) had cTnI

Discussion

We found that varying the diagnostic threshold for cTnI resulted in clinically and statistically significant differences in the number of patients diagnosed with AMI. The number of additional patients diagnosed was highly dependent on the CK-MB standard used for comparison, as well as the ischemic risk of the patient population. Mortality was highest in patients who had CK-MB MI, intermediate in those who had cTnI MI but not CK-MB MI, and lowest in those without CK-MB MI or cTnI MI.

The

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