Bedside troponin T testing is not useful for early out-of-hospital diagnosis of myocardial infarction

Predictive value of routine point-of-care cardiac troponin T measurement for prehospital diagnosis and risk-stratification in patients with suspected acute myocardial infarction

OBJECTIVE

The purpose of this study was to determine the predictive value of routine prehospital point-of-care cardiac troponin T measurement for diagnosis and risk stratification of patients with suspected acute myocardial infarction.

METHODS AND RESULTS

All prehospital emergency medical service vehicles in the Central Denmark Region were equipped with a point-of-care cardiac troponin T device (Roche Cobas h232) for routine use in all patients with a suspected acute myocardial infarction. During the study period, 1 June 2012-30 November 2015, prehospital point-of-care cardiac troponin T measurements were performed in a total of 19,615 cases seen by the emergency medical service and 18,712 point-of-care cardiac troponin T measurements in 15,781 individuals were matched with an admission. A final diagnosis of acute myocardial infarction was confirmed in 2187 cases and a total of 2150 point-of-care cardiac troponin T measurements (11.0%) had a value ≥50 ng/l, including 966 with acute myocardial infarction (sensitivity: 44.2%, specificity: 92.8%). Patients presenting with a prehospital point-of-care cardiac troponin T value ≥50 ng/l had a one-year mortality of 24% compared with 4.8% in those with values <50 ng/l, log-rank: p<0.001. The following variables showed the strongest association with mortality in multivariable analysis: point-of-care cardiac troponin T≥50 ng/l (hazard ratio 2.10, 95% confidence interval: 1.90-2.33), congestive heart failure (hazard ratio 1.93, 95% confidence interval: 1.74-2.14), diabetes mellitus (hazard ratio 1.42, 95% confidence interval: 1.27-1.59) and age, one-year increase (hazard ratio 1.08, 95% confidence interval: 1.08-1.09).

CONCLUSIONS

Patients with suspected acute myocardial infarction and a prehospital point-of-care cardiac troponin T ≥50 ng/l have a poor prognosis irrespective of the final diagnosis. Routine troponin measurement in the prehospital setting has a high predictive value and can be used to identify high-risk patients even before hospital arrival so that they may be re-routed directly for advanced care at an invasive centre.

Prehospital diagnosis of patients with acute myocardial infarction

Primary percutaneous intervention (PPCI) is the preferred treatment in patients with ST elevation myocardial infarction (STEMI) if this can be performed in a timely manner. The

Prehospital factors associated with an acute life-threatening condition in non-traumatic chest pain patients - A systematic review

BACKGROUND

Chest pain is a common symptom among patients contacting the emergency medical services (EMS). Risk stratification of these patients is warranted before arrival in hospital, regarding likelihood of an acute life-threatening condition (LTC).

AIM

To identify factors associated with an increased risk of acute LTC among patients who call the EMS due to non-traumatic chest pain.

METHODS

Several databases were searched for relevant articles. Identified articles were quality-assessed using the Scottish Intercollegiate Guidelines Network checklists. Extracted data was analysed using a semi-quantitative synthesis evaluating the level of evidence of each identified factor.

RESULTS

In total, 10 of 1245 identified studies were included. These studies provided strong evidence for an increased risk of an acute LTC with increasing age, male gender, elevated heart rate, low systolic blood pressure and ST elevation or ST depression on a 12-lead ECG. The level of evidence regarding the history of myocardial infarction, angina pectoris or presence of a Q wave or a Left Bundle Branch Block on the ECG was moderate. The evidence was inconclusive regarding dyspnoea, cold sweat/paleness, nausea/vomiting, history of chronic heart failure, smoking, Right Bundle Branch Block or T-inversions on the ECG.

CONCLUSIONS

Factors reflecting age, gender, myocardial ischemia and a compromised cardiovascular system predicted an increased risk of an acute life-threatening condition in the prehospital setting in cases of acute chest pain. These factors may form the basis for prehospital risk stratification in acute chest pain.

Quantitative point-of-care troponin T measurement for diagnosis and prognosis in patients with a suspected acute myocardial infarction

Improvement of prehospital triage is essential to ensure rapid management of patients with acute myocardial infarction (AMI). This study evaluates the feasibility of prehospital quantitative point-of-care cardiac troponin T (POC-cTnT) analysis, its ability to identify patients with AMI, and its capacity to predict mortality. The study was performed in the Central Denmark Region from May 2010 to May 2011. As a supplement to electrocardiography, a prehospital POC-cTnT measurement was performed by a paramedic in patients with suspected AMI. AMI was diagnosed according to the universal definition of myocardial infarction using the ninety-ninth percentile upper reference level as diagnostic cut point. The paramedics performed POC-cTnT measurements in 985 subjects with a symptom duration of 70 minutes (95% CI, 35 to 180); of whom, 200 (20%) had an AMI. The prehospital sample was obtained 88 minutes (range, 58 to 131) before the sample made on admission to the hospital. The sensitivity for detection of patients with an AMI was 39% (95% CI, 32% to 46%) and the diagnostic accuracy of the POC-cTnT values was 0.67 (95% CI, 0.64 to 0.71). Adjusted survival analysis showed a strong significant association between elevated prehospital POC-cTnT level above the detection level of 50 ng/L and mortality in patients with a suspected AMI irrespective of whether an AMI was diagnosed. In conclusion, large-scale quantitative prehospital POC-cTnT testing by paramedics is feasible. An elevated prehospital POC-cTnT value contains diagnostic information and is highly predictive of mortality in patients with a suspected AMI.

Clinical usefulness of measuring red blood cell distribution width on admission in patients with acute coronary syndromes

BACKGROUND

Conventional cardiac markers used for the biochemical diagnosis of acute coronary syndromes (ACS) have a high specificity but low sensitivity within 2-4 h of symptoms onset. The red blood cell distribution width (RDW), reflecting the size variability of circulating red blood cells, has been shown to be independently associated with an increased risk of major cardiovascular events. We assessed whether there is an association between RDW at admission and cardiac troponin T (cTnT) elevation in patients with chest pain.

METHODS

We analyzed RDW values in 2304 adult patients, who were consecutively admitted over a 1-year period to the local emergency department for chest pain suggestive of ACS. In all patients, a baseline blood sample was collected for routine haematological testing, whereas cTnT was measured at baseline and after 4, 6, and 12 h.

RESULTS

A total of 456 patients (19.8% of total) had ACS. These patients, all having cTnT> or =0.03 microg/L up to 12 h from admission other than ischaemic electrocardiographic changes, had higher RDW than non-ACS patients [median 15.1%, (5th-95th percentiles) 13.2%-19.0% vs. 13.5%, 12.9%-17.1%, p<0.001]. On admission, the sensitivity and specificity of cTnT were 94% (25 false negative results) and 100%, respectively. The diagnostic accuracy of RDW, as calculated by the receiver operating characteristic curve analysis, was 0.705 (p<0.001). At the cut-off value of 14%, the clinical sensitivity and specificity of RDW on admission were 79% and 50%, respectively. In 21 out of 25 patients classified as false negative for cTnT on admission, the RDW was >14%. Accordingly, the diagnostic sensitivity of the two combined measurements on admission was 99%.

CONCLUSIONS

As RDW is widely available to clinicians as a part of the complete blood count, and therefore incurs no additional costs, it might be considered with other conventional cardiac markers for the risk stratification of ACS patients admitted to emergency departments.

The value of biochemical markers for risk stratification prior to hospital admission in acute chest pain

We describe the use of biochemical markers in the pre-hospital setting with regard to diagnostic accuracy for the detection of an acute myocardial infarction (AMI) and for prognosis in connection with acute chest pain. The sensitivity has been reported to be limited; blood sampling occurs very early and often prior to the release of biochemical markers into the circulation. The specificity was in some studies also limited, but this is more difficult to explain. New biochemical markers like human heart fatty acid binding protein (H-FACB) have shown improved diagnostic accuracy, in the pre-hospital setting, in one small pilot study compared with traditional biochemical markers like troponins, creatine kinase (CK-MB) and myoglobin. However, in a recent small study, the sensitivity for troponin I (when a low decision limit for myocardial damage was used), when analysed prior to hospital admission, was reported to be very high. The latter data need to be confirmed in larger studies and various biochemical markers reflecting various pathophysiological aspects of the disease need to be tested before the analysis of any marker can be recommended for use in the pre-hospital setting of a suspected AMI.

[Acute coronary syndrome in the prehospital phase]

Cardiovascular diseases are the number one cause of death in Germany. In 2002 about 70,000 people died of acute myocardial infarction (AMI) and of these 37% died before arrival at hospital which underlines the relevance of adequate prehospital care. The generic term acute coronary syndrome (ACS) was introduced because a single pathomechanism accounts for the different forms and comprises unstable angina pectoris (iAP), non-ST-elevation myocardial infarction (NSTEMI), ST-elevation myocardial infarction (STEMI) and sudden cardiac death (SCD). Characteristic features are retrosternal pain, vegetative symptoms and radiation of pain into the adjoining regions. Further differentiation can only be achieved by the 12-lead ECG, as cardiac-specific enzymes do not play a role in prehospital decisions. Prehospital delays should be avoided, history and physical examination should be brief but focused, vital parameters should be assessed and monitored. Basic treatment for ACS should comprise inhalative oxygen, nitrates, morphine, aspirin and beta-blockers. If STEMI is diagnosed, patients with symptoms <12 h should undergo fibrinolytic therapy unless there is primary percutaneous coronary intervention (PCI) available within 90 min or if contraindicated. Heparin should be given to patients with STEMI depending on the choice of fibrinolytic agent, it otherwise results in a higher risk of bleeding, but in patients with iAP or NSTEMI it reduces mortality. All patients must be accompanied by the emergency physician during transportation and should be brought to a hospital with primary PCI, especially those with complicated ACS. Treatment of complications depends largely on the type, persistence and severity.

Cardiac troponins

Cardiac troponins I and T are proteins integral to the function of cardiac muscle. They are very sensitive markers for the detection of myocardial damage, and the ability to assay their serum levels accurately and quickly have revolutionized the concepts of minor myocardial injury and infarction. They are also powerful prognostic indicators of future adverse cardiac events. Limitations, more of troponin T than I, include decreased specificity in renal failure and skeletal muscle disease. Rapid, whole blood assays are now available that can be done at the patient's bedside. This review discusses the cardiac troponins, their biochemistry, the assays for them currently available, and their roles in the evaluation of cardiac disease in the Emergency Department (ED).

Point of care testing in the emergency department

Point of care (POC) testing in the Emergency Department (ED) is becoming more common. The implementation and maintenance of POC testing in the ED, however, is a complex issue. We performed a systematic review of the English language literature published between 1985 and June 2001 with a focus on POC testing and ED application. Articles that addressed the following were included in the review: implementation of POC testing, maintenance and regulation of POC testing, and application of POC testing. Current POC technology has been found to be reliable in various patient care settings, including the ED. Cost and connectivity issues are complex and difficult to assess, making these the greatest barriers to the full acceptance of POC testing in the ED. Patient care issues must be weighed against the cost of implementing POC testing and supporting the infrastructure needed to maintain this technology in the ED.

Accuracy of biomarkers to diagnose acute cardiac ischemia in the emergency department: a meta-analysis

STUDY OBJECTIVE

We sought to evaluate quantitatively the evidence on the diagnostic performance of presentation and serial biochemical markers for emergency department diagnosis of acute cardiac ischemia (ACI), including acute myocardial infarction (AMI) and unstable angina.

METHODS

We conducted a systematic review and meta-analysis of the English-language literature published between 1966 and December 1998. We examined the diagnostic performance of creatine kinase, creatine kinase-MB, myoglobin, and troponin I and T testing. Diagnostic performance was assessed by using estimates of test sensitivity and specificity and was summarized by summary receiver-operating characteristic curves.

RESULTS

Only 4 studies were found that evaluated all patients with ACI; 73 were found that focused only on a diagnosis of AMI. To diagnose ACI, presentation biomarker tests had sensitivities of 16% to 19% and specificities of 96% to 100%; serial biomarker tests had sensitivities of 31% to 45% and specificities of 95% to 98%. Considering only the diagnosis of AMI, presentation biomarker tests had summary sensitivities of 37% to 49% and summary specificities of 87% to 97%; serial biomarker tests had summary sensitivities of 79% to 93% and summary specificities of 85% to 96%. Variation of test sensitivity was best explained by test timing. Longer symptom duration or time between serial tests yielded higher sensitivity.

CONCLUSION

The limited evidence available to evaluate the diagnostic accuracy of biomarkers for ACI suggests that biomarkers have very low sensitivity to diagnose ACI. Thus, biomarkers alone will greatly underdiagnose ACI and will be inadequate to make triage decisions. For AMI diagnosis alone, multiple testing of individual biomarkers over time substantially improves sensitivity, while retaining high specificity, at the expense of additional time. Further high-quality studies are needed on the clinical effect of using biomarkers for patients with ACI in the ED and on optimal timing of serial testing and in combination with other tests.