Predicting a late positive serum troponin in initially troponin-negative patients with non-ST-elevation acute coronary syndrome: clinical predictors and validated risk score results from the TIMI IIIB and GUSTO IIA studies.

BACKGROUND: Troponin testing is useful for evaluating patients with non-ST-segment elevation acute coronary syndromes (NSTE ACS); however, a significant percentage of patients are troponin negative at presentation and develop late rise of the marker.

METHODS: Patients in the TIMI IIIB study were assessed with respect to their troponin I (TnI) status at presentation and 12 hours. Multivariable analysis identified independent clinical factors associated with TnI rise at 12 hours among subjects initially TnI negative. A score predicting late TnI rise in TIMI IIIB was developed using these factors and validated among patients in the GUSTO IIA study.

RESULTS: Of 1342 subjects in TIMI IIIB, 200 (14.9%) were negative at baseline, but developed an elevated TnI (> or = 0.4 ng/mL) at 12 hours. Six independent predictors of late TnI rise were identified: ST-segment deviation (odds ratio [OR] 3.52, 95% CI 2.38-5.23, P < .001), presentation < 8 hours from symptom onset (OR 2.91, 95% CI 1.92-4.40, P < .001), no prior percutaneous coronary intervention (OR 2.88, 95% CI 1.54-5.39, P = .001), no prior beta-blocker use (OR 1.74, 95% CI 1.15-2.63, P = .008), unheralded angina (OR 1.65, 95% CI 1.12-2.42, P = .01), and a history of myocardial infarction (OR 1.59, 95% CI 1.06-2.37, P = .02). ST deviation, presentation < 8 hours from symptoms, and no prior percutaneous coronary intervention were given a score of 2 points, whereas a score of 1 point was assigned to the other factors. Among baseline TnI-negative patients, a rising score was paralleled by an increasing prevalence of late TnI rise from 0% (with a score of 0) to 69% (with a score of 9) (P < .001). In confirmation, the score was able to similarly predict late troponin T rise among 855 patients in the GUSTO IIA study (P < .0001).

CONCLUSION: Development of late troponin rise is common in non-ST-segment elevation acute coronary syndromes. Six easily ascertained variables may be used to identify those at higher risk for late rise in troponin levels after an initially negative presentation.