Could a Six-Hour multimarker protocol be accurate to predict acute coronary syndromes in chest pain patients admitted to an observational unit in an emergency department?

Study objectives: Actual guidelines suggest an 8- to 12-hour protocol to evaluate low-risk chest pain patients in the emergency department (ED). Recent reports studied shorter protocol (6 to 8 hours) with a single marker of myocardial damage. We compared clinical efficacy and safety of 2 multimarker protocols (MMP) of 6 hours and 9 hours for risk stratification of chest pain. Methods: This is an observational, longitudinal, prospective study of 175 consecutive chest pain patients admitted to our urban hospital from January to June 2003 for chest pain of less than 12 hours' duration at low to moderate risk of acute coronary syndrome (ACS). We excluded 275 patients because of incomplete data, other causes of chest pain, and ST-segment elevation at initial ECG. All patients underwent 12-lead ECG and continuous ST monitoring. Two MMPs were MMP-6 and MMP-9: myoglobin plus creatine kinase (CK)–MB and troponin I (cTnI) at 0, 3, and 6 hours and at 0, 3, 6, and 9 hours after admission. They were positive if 1 marker was above the upper limit of normal (105 ng/mL for myoglobin, 4 ng/mL for CK-MB, 0.1 ng/mL for cTnI). We used a Dade-Behring Stratus immunoassay test. A 30-day follow-up was performed to relate MMP status to death or myocardial infarction. Graded exercise tests after negative MMP were performed. We tested sensitivity, specificity, and negative-positive predictive values (NPV-PPV) with confidence intervals (CIs) for all outcomes in 2 MMP. To test MMP safety, we performed a longer 6-month follow-up for primary outcomes (death and ACS) of patients discharged after negative MMP. Student's t or χ 2 test was used to compare 2 groups. Results: Eighty-five patients were included in MMP-6 and 90 in MMP-9, mean age 64.8 and 58.6 years ( P P >.05), and similar graded exercise test results: 1.5% of examinations ischemic for both groups of patients ( P =.66). After multimarker serial testing, more patients were positive with MMP-9 (MMP-9 = 27.7%; MMP-6 = 22.3%, P =.47). Two protocols had similar median time from symptom onset to ED arrival: 3.9 hours for MMP-6 and 3.7 hours for MMP-9. The relation between MMP status after serial testing and 30-day death or infarction was stronger for both protocols (MMP-6: positive, 15.8% event rate versus negative 0.0%, P P Conclusion: Our data suggest that MMP 6 hours and MMP 9 hours had a good and similar accuracy for short-term outcomes. A short multimarker strategy testing several markers of myocardial necrosis with different time-to-positive profiles could save time. Moreover, it could improve risk stratification for death and ACS and management of chest pain patients in the observation unit of the ED. Study limitations are few patients for which to perform multivariable logistic regression to check the influence of other variables on outcomes.