Diagnostic Accuracy of a New High-Sensitivity Troponin I Assay and Five Accelerated Diagnostic Pathways for Ruling Out Acute Myocardial Infarction and Acute Coronary Syndrome

STUDY OBJECTIVE

This diagnostic accuracy study describes the performance of 5 accelerated chest pain pathways, calculated with the new Beckman's Access high-sensitivity troponin I assay.

METHODS

High-sensitivity troponin I was measured with presentation and 2-hour blood samples in 1,811 patients who presented to an emergency department (ED) in Australia. Patients were classified as being at low risk according to 5 rules: modified accelerated diagnostic protocol to assess patients with chest pain symptoms using troponin as the only biomarker (m-ADAPT), the Emergency Department Assessment of Chest Pain Score (EDACS) pathway, the History, ECG, Age, Risk Factors, and Troponin (HEART) pathway, the No Objective Testing Rule, and the new Vancouver Chest Pain Rule. Endpoints were 30-day acute myocardial infarction and acute coronary syndrome. Measures of diagnostic accuracy for each rule were calculated.

RESULTS

Data included 96 patients (5.3%) with acute myocardial infarction and 139 (7.7%) with acute coronary syndrome. The new Vancouver Chest Pain Rule and No Objective Testing Rule had high sensitivity for acute myocardial infarction (100%; 95% confidence interval [CI] 96.2% to 100% for both) and acute coronary syndrome (98.6% [95% CI 94.9% to 99.8%] and 99.3% [95% CI 96.1% to 100%]). The m-ADAPT, EDACS, and HEART pathways also yielded high sensitivity for acute myocardial infarction (96.9% [95% CI 91.1% to 99.4%] for m-ADAPT and 97.9% [95% CI 92.7% to 99.7%] for EDACS and HEART), but lower sensitivity for acute coronary syndrome (≤95.0% for all). The m-ADAPT, EDACS, and HEART rules classified more patients as being at low risk (64.3%, 62.5%, and 49.8%, respectively) than the new Vancouver Chest Pain Rule and No Objective Testing Rule (28.2% and 34.5%, respectively).

CONCLUSION

In this cohort with a low prevalence of acute myocardial infarction and acute coronary syndrome, using the Beckman's Access high-sensitivity troponin I assay with the new Vancouver Chest Pain Rule or No Objective Testing Rule enabled approximately one third of patients to be safely discharged after 2-hour risk stratification with no further testing. The EDACS, m-ADAPT, or HEART pathway enabled half of ED patients to be rapidly referred for objective testing.

Rational clinical evaluation of suspected acute coronary syndromes: The value of more information

OBJECTIVE

Many meta-analyses have provided synthesised likelihood ratio data to aid clinical decision-making. However, much less has been published on how to safely combine clinical information in practice. We aimed to explore the benefits and risks of pooling clinical information during the ED assessment of suspected acute coronary syndrome.

METHODS

Clinical information on 1776 patients was collected within a randomised trial conducted across five South Australian EDs between July 2011 and March 2013. Bayes theorem was used to calculate patient-specific post-test probabilities using age- and gender-specific pre-test probabilities and likelihood ratios corresponding to the presence or absence of 18 clinical factors. Model performance was assessed as the presence of adverse cardiac outcomes among patients theoretically discharged at a post-test probability less than 1%.

RESULTS

Bayes theorem-based models containing high-sensitivity troponin T (hs-troponin) outperformed models excluding hs-troponin, as well as models utilising TIMI and GRACE scores. In models containing hs-troponin, a plateau in improving discharge safety was observed after the inclusion of four clinical factors. Models with fewer clinical factors better approximated the true event rate, tended to be safer and resulted in a smaller standard deviation in post-test probability estimates.

CONCLUSIONS

We showed that there is a definable point where additional information becomes uninformative and may actually lead to less certainty. This evidence supports the concept that clinical decision-making in the assessment of suspected acute coronary syndrome should be focused on obtaining the least amount of information that provides the highest benefit for informing the decisions of admission or discharge.

Retrospective observational study of patients who present to Australian rural emergency departments with undifferentiated chest pain

OBJECTIVE

To identify the demographic and clinical characteristics of patients who present to Australian rural emergency departments (EDs) with chest pain.

DESIGN

Retrospective, observational study.

SETTING

Rural EDs in Queensland, Australia.

PARTICIPANTS

Three hundred thirty-seven consecutive adult patients with undifferentiated chest pain who presented between 1 September 2013 and 30 November 2013.

MAIN OUTCOME MEASURES

Service indicators, discharge diagnoses and disposition.

RESULTS

Presentations for undifferentiated chest pain represented 3.5% of all patient presentations during the sampling period. The mean age of patients was 48 years and 54% were male. Overall, 92% of patients left the ED within the 4-hour NEAT target. The majority of presentations were related to cardiac concerns (39%), followed by non-cardiac chest pain (17%), musculoskeletal (15%) and respiratory (10%) conditions. More than half of these patients were discharged at the completion of the ED service (52.8%), 40.6% were admitted, 3.3% left at own risk, 2.4% did not wait and less than 1% of patients required transfer to another hospital directly from the ED.

CONCLUSIONS

This study has provided information on the characteristics and processes of care for patients presenting to Australian rural EDs with undifferentiated chest pain that will inform service planning and further research to evaluate the effectiveness of care for these patients.

Diagnostic Yield of Routine Stress Testing in Low and Intermediate Risk Chest Pain Patients Under 40 Years: A Systematic Review

OBJECTIVE

Chest pain is one of the most frequent causes for presentation to emergency departments (EDs). The majority of patients will undergo diagnostic workup including stress testing to rule out an acute coronary syndrome, but very few patients will be diagnosed with a cardiac cause for their pain. Patients under 40 years represent a lower risk group in which routine stress testing may be of little benefit. This systematic review sought to determine the diagnostic yield of routine stress testing in low- and intermediate-risk chest pain patients under 40 years.

METHODS

Electronic databases were searched for relevant studies. The quality of the included primary studies was assessed using the National Health and Medical Research Council evidence hierarchy and the McMaster Critical Appraisal Tool for Quantitative Studies. Descriptive statistics summarized the findings.

RESULTS

Five primary studies were included in the review (all level III-3 evidence); 7 additional sources of relevant data were also included. Diagnostic yield of routine stress testing in low- and intermediate-risk patients under 40 years is reported between 0% and 1.1%. Combined data from included primary studies demonstrated just 4 out of 1683 true positive stress tests (0.24%), only one of which was definitively confirmed by coronary angiogram; additional data sources identified just 1 out of 310 true positive stress tests (0.32%).

CONCLUSIONS

Diagnostic yield of routine stress testing in low- and intermediate-risk chest pain patients under 40 years is low. However, better quality studies are required to be able to draw definitive conclusions.

Change to costs and lengths of stay in the emergency department and the Brisbane protocol: an observational study

OBJECTIVE

To compare health service cost and length of stay between a traditional and an accelerated diagnostic approach to assess acute coronary syndromes (ACS) among patients who presented to the emergency department (ED) of a large tertiary hospital in Australia.

DESIGN, SETTING AND PARTICIPANTS

This historically controlled study analysed data collected from two independent patient cohorts presenting to the ED with potential ACS. The first cohort of 938 patients was recruited in 2008-2010, and these patients were assessed using the traditional diagnostic approach detailed in the national guideline. The second cohort of 921 patients was recruited in 2011-2013 and was assessed with the accelerated diagnostic approach named the Brisbane protocol. The Brisbane protocol applied early serial troponin testing for patients at 0 and 2 h after presentation to ED, in comparison with 0 and 6 h testing in traditional assessment process. The Brisbane protocol also defined a low-risk group of patients in whom no objective testing was performed. A decision tree model was used to compare the expected cost and length of stay in hospital between two approaches. Probabilistic sensitivity analysis was used to account for model uncertainty.

RESULTS

Compared with the traditional diagnostic approach, the Brisbane protocol was associated with reduced expected cost of $1229 (95% CI -$1266 to $5122) and reduced expected length of stay of 26 h (95% CI -14 to 136 h). The Brisbane protocol allowed physicians to discharge a higher proportion of low-risk and intermediate-risk patients from ED within 4 h (72% vs 51%). Results from sensitivity analysis suggested the Brisbane protocol had a high chance of being cost-saving and time-saving.

CONCLUSIONS

This study provides some evidence of cost savings from a decision to adopt the Brisbane protocol. Benefits would arise for the hospital and for patients and their families.

Performance of risk stratification for acute coronary syndrome with two-hour sensitive troponin assay results

BACKGROUND

Risk stratification processes for patients with possible acute coronary syndrome (ACS) recommend the use of serial sensitive troponin testing over at least 6h. Troponin assays vary in their analytical performance. Utility in accurate risk stratification at 2h post-presentation is unknown.

METHODS

A diagnostic accuracy study of patients presenting to the emergency department (ED) with symptoms of ACS was performed. Troponin was measured at 0, 2 and 6h post-presentation. Acute myocardial infarction (AMI) was adjudicated by cardiologists and incorporated the 0 and 6h troponin values measured by a sensitive troponin assay. Results were described using standard measures of test accuracy.

RESULTS

Of the 685 patients, 51 (7.4%) had 30-day AMI or cardiac death, and 76 (11.1%) had secondary outcomes (all cause death, ACS and revascularisation procedures). There was no significant difference in the diagnostic accuracy of early versus late biomarker strategies when used with the current risk stratification processes. Incorporation of a significant delta did not improve the stratification at 2h post-presentation.

CONCLUSIONS

Accelerated risk stratification of patients with ACS symptoms may occur at 2h post-presentation using troponin results measured by a sensitive assay. Incorporation of such a strategy could support improvements in patient flow within EDs.

The approach to patients with possible cardiac chest pain

Chest pain is a common reason for presentation in hospital emergency departments and general practice. Some patients presenting with chest pain to emergency departments and, to a lesser extent, general practice will be found to have a life-threatening cause, but most will not. The challenge is to identify those who do in a safe, timely and cost-effective manner. An acute coronary syndrome cannot be excluded on clinical grounds alone. In patients with ongoing symptoms of chest pain, without an obvious other cause, ST-segment-elevation myocardial infarction should be excluded with a 12-lead electrocardiogram at the first available opportunity. Significant recent advances in the clinical approach to patients with acute chest pain, including better understanding of risk stratification, increasingly sensitive cardiac biomarkers and new non-invasive tests for coronary disease, can help clinicians minimise the risk of unexpected short-term adverse cardiac events. An approach that integrates these advances is needed to deliver the best outcomes for patients with chest pain. All hospital emergency departments should adopt such a strategic approach, and general practitioners should be aware of when and how to access these facilities.