Enhancing the diagnostic performance of troponins in the acute care setting.

BACKGROUND: Current guidelines define cardiac troponin I (TnI) as an indicator of necrosis when the concentration exceeds the 99% upper limit of a healthy reference population, a reference value near the assay's lowest detectable level. We assessed the utility of a modified TnI cutoff point derived from a population at low risk for coronary artery disease (CAD) and evaluated its utility in determining acute myocardial infarction (MI). METHODS: A modified TnI cutoff point was derived by the receiver operating characteristic (ROC) curve from 737 consecutive patients who underwent serial TnI measurements for exclusion of MI. Creatinine kinase isoenzyme MB (CK-MB) evolutionary change was used to define MI. The new derived cutoff point was validated using another subset of 320 patients who were evaluated for MI. RESULTS: ROC-derived TnI cutoff point (A) was 0.65 µg/L, and its performance was compared to the recommended cutoff point ([B] 0.15 µg/L). Cutoff point A had greater specificity (94.5% vs. 86.9%, p < 0.001) but slightly lower sensitivity (96.5% vs. 100%, p < 0.01). Cutoff point A provided significantly greater positive predictive value (PPV) for MI (74.1% vs. 55.5%, p < 0.0001) and fewer false-positive errors, while preserving comparable negative predictive value (NPV) (98.9% vs. 100%). CONCLUSION: A higher cutoff point derived from a reference population of patients at low risk for CAD may improve the TnI performance assay. The PPV for diagnosis of MI was significantly higher and false-positive values were fewer without affecting the NPV. The more reliable diagnosis of MI may have resulted, which, in turn, may have significant clinical and economic implications.

Incidence of caffeine in serum of patients undergoing dipyridamole myocardial perfusion stress test by an intensive versus routine caffeine history screening.

The coronary vasodilatory effect of dipyridamole is competitively blocked by caffeine. The purposes of this study were to (1) assess the incidence of having detectable serum caffeine and (2) evaluate whether an intensive caffeine history screening strategy was superior to routine history screening before dipyridamole myocardial perfusion imaging. One hundred ninety-four patients who were randomized to an intensive or a routine screening history strategy were prospectively evaluated. Serum caffeine levels were determined in all patients. Outcomes data, including death, nonfatal myocardial infarction, and history of revascularization, were obtained at 24 months. Nearly 1 in 5 patients (19%) who screened negative by history had detectable serum caffeine. In patients who screened negative by history, there was no statistically significant difference in the percentage of caffeine seropositivity between the intensive and routine arms (16% vs 22%, respectively, p = 0.31). The incidence of combined end points of death, myocardial infarction, or revascularization was 22.9% and 7.3% in patients with and without detectable serum caffeine, respectively (p = 0.01). In conclusion, despite initial negative results on screening by history, a considerably high percentage of patients had positive serum caffeine levels. These results do not support the use of an intensive screening strategy. Detectable serum caffeine was associated with a higher incidence of adverse outcomes.

Clinical characteristics predict benefits from eptifibatide therapy during coronary stenting: insights from the Enhanced Suppression of the Platelet IIb/IIIa Receptor With Integrilin Therapy (ESPRIT) trial.

OBJECTIVES: In order to determine a differential benefit from treatment, we compared the long-term outcome of high-risk versus low-risk patients and evaluated survival free from death or myocardial infarction at one year. BACKGROUND: Newer anticoagulant strategies during percutaneous coronary intervention have necessitated a reanalysis of the role of intravenous GP IIb/IIIa inhibitors. The Enhanced Suppression of the Platelet IIb/IIIa Receptor with Integrilin Therapy trial randomized 2,064 patients undergoing nonurgent coronary stent implantation to eptifibatide or placebo. METHODS: High-risk characteristics were defined as age >75 years, diabetes, elevated cardiac markers, ST-segment elevation myocardial infarction within 7 days, or unstable angina within 48 h of randomization. Age <5 years, absence of diabetes, and any other reason for admission were considered low risk characterstics. RESULTS: There were 1,018 patients in the high-risk group (50.8% eptifibatide, 49.2% placebo) and 1,045 patients in the low-risk group (50.0% eptifibatide, 50.0% placebo). Baseline demographics were similar in both groups except for more hypertension (63% vs. 55%, respectively), peripheral vascular disease (8.2% vs. 5.2%, respectively), prior stroke (5.5% vs. 3.2%, respectively), and female gender (33% vs. 22%, respectively) in the high-risk than the low-risk group. At one year, the composite end point of death or myocardial infarction occurred in 15.89% of placebo patients and 7.99% of eptifibatide patients in the high-risk group and 9.02% of the placebo and 8.11% of eptifibatide patients in the low-risk group. CONCLUSIONS: Although eptifibatide treatment improved outcomes for all patients, preprocedural clinical characteristics can define a subgroup of patients who may derive greatest benefit from its use during coronary stent placement.