Usefulness of a new rapid bedside troponin T assay in patients with chest pain

The sensitivity of cardiac markers stratified by symptom duration

We compared the sensitivity of three commonly used cardiac markers between two subpopulations, those who came to the Emergency Department (ED) late (6-24 h) after their symptoms began, and those who arrived earlier (<6 h), in a prospective comparative trial. Among all adult patients who presented to our ED with symptoms suggestive of acute myocardial infarction (MI), we drew serum for myoglobin, CK-MB, and troponin I upon arrival (time 0) and 2 h later. Outcomes, including acute MI, were determined. Sensitivities for all three markers between the subpopulations who arrived fewer than 6 h from symptom onset were compared to those who arrived later (6-24 h). We enrolled 346 eligible subjects, 36% of whom described cardiac symptoms as beginning 6 or more hours earlier; 14% suffered acute MIs. For time 0, the sensitivity of all three markers for acute MI was significantly higher among those subjects with symptoms of 6 or more hours' duration as compared to those with less. For troponin I, the increase in sensitivity between these two subpopulations approached 300%. At the time of the 2-h sample, the differences in sensitivities were much less and were not statistically significant. We conclude that cardiac marker values obtained at time 0 among Emergency Department patients who arrive 6 or more hours after cardiac symptom onset provide significantly higher sensitivities as compared to those obtained in patients who arrive earlier. For troponin I, the increase in sensitivity approaches threefold.

Elevated cardiac troponin T in hemodialysis patients receiving more intravenous iron sucrose

Elevated cardiac troponin T (cTnT) has been associated with shorter survival in hemodialysis patients. Moreover, intravenous (IV) iron treatment has been held responsible for oxidative stress and accelerated atherosclerosis in these patients. In the present study, we investigated the relationship between cTnT concentration, IV iron treatment, and parameters of iron status. In addition, parameters of oxidative stress, inflammation, and atherosclerosis were evaluated. Predialysis blood samples of 78 chronic hemodialysis patients were analyzed for cTnT, malondialdehyde, creatine kinase (CK), and CK-isoenzyme MB (CK-MB). In addition, the mean value of predialysis serum samples collected during the last year, were considered for homocysteine, ferritin, iron, iron binding capacity, blood cell counts, blood urea nitrogen, creatinine, albumin, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), calcium, phosphate, iPTH, cholesterol, and triglyceride. The quantity of IV iron sucrose administered during the last two years was counted from the patients' files. Echocardiography, all events related to ischemic heart disease, and urine volume were also recorded. Elevated cTnT levels (> or =0.10 ng/mL) were found in 18 patients (23.1%). The amount of iron administered was 2264+/-1871 mg with a range 0-7000 mg. Patients with elevated cTnT levels received more IV iron than those with normal cTnT (3692+/-1771 vs. 1761+/-1595 mg, p<0.001). The serum ferritin level was higher in patients with elevated cTnT (median levels; 477 vs. 288 ng/mL; P<0.05). Patients with elevated cTnT were longer on dialysis compared to those with normal levels (median times; 35.5 vs. 15 months, P<0.01) and regression analysis identified the amount of administered iron as an independent factor for elevated cTnT (P<0.01). Intravenous iron treatment and high ferritin concentration are related to high cTnT level, which has previously been incriminated as a survival marker in hemodialysis patients.

Ruling out myocardial infarction with troponin T and creatine kinase MB mass: diagnostic and prognostic aspects

OBJECTIVE

To investigate the time window for ruling out myocardial infarction (MI) with troponin T (TnT) and creatine kinase isoenzyme MB mass (CK-MBm) and the prognosis of patients with ruled-out MI diagnosis.

DESIGN

The study was based on 397 patients admitted with a suspected acute coronary syndrome but with relief of symptoms within 24 h.

RESULTS

MI diagnosis was confirmed with elevated TnT (>0.10 microg/l) in 108 patients. in 91% within 12-24 h from the onset of symptoms, and in 99% within 12 h from admission. In 94 of these patients CK-MBm became elevated (>5.0 microg/l). in 95% within 10-12 h from the onset of symptoms, and in 99% within 6 h from admission. Among patients with ruled-out MI diagnosis, the 1-year incidence of recurrent coronary events was 29% in those with positive history of coronary heart disease (CHD) but only 7% in those without prior CHD (p < 0.001).

CONCLUSION

Using TnT or CK-MBm, MI can be ruled out within 12 h from admission in the majority of patients. Among patients with ruled-out MI diagnosis, positive history of CHD is an important determinant of prognosis.

Measurement of cardiac troponins

The cardiac troponins form part of the regulatory mechanism for muscle contraction. Specific cardiac isoforms of cardiac troponin T and cardiac troponin I exist and commercially available immunoassay systems have been developed for their measurement. A large number of clinical and analytical studies have been performed and the measurement of cardiac troponins is now considered the 'gold standard' biochemical test for diagnosis of myocardial damage. There have been advances in understanding the development and structure of troponins and their degradation following myocardial cell necrosis. This has contributed to the understanding of the problems with current assays. Greater clinical use has also highlighted areas of analytical and clinical confusion. The assays are reviewed based on manufacturers' information, current published material as well as the authors' in-house experience.

Clinical application of rapid quantitative determination of cardiac troponin-T in an emergency department setting

OBJECTIVES

We analysed the clinical use of Troponin-T compared to creatine kinase MB in a non-trauma emergency department setting.

BACKGROUND

A newly established single specimen quantitative Troponin T assay allows the clinical application of this parameter. METHODS. Five-hundred Troponin T tests were provided for use by emergency physicians who could combine them with the routine laboratory tests without restriction as to the indication or number of tests per patient. The number of tests per patient, time frame, final diagnosis and additional clinical information gained were recorded. All patients were followed for at least 6 months to verify the diagnosis and to assess the occurrence of cardiac events (nonfatal AMI or cardiac death). The ability of Troponin T and creatine kinase MB tests to predict cardiac events within 6 months were compared.

RESULTS

The 500 Troponin T tests were used in 249 patients (median two tests per patient (range 1-5)) within 41 days. The final diagnosis revealed coronary heart disease in 85, non-coronary heart disease in 39, non-cardiac chest pain in 86 and other diagnoses in 39 of the patients. In 14 patients with an elevated creatine kinase MB, myocardial damage could safely be ruled out by a negative Troponin T, in six patients with a normal creatine kinase MB minor myocardial damage could be detected by a positive Troponin T. During follow up 28 cardiac events were recorded. Troponin T had a significantly higher specificity, positive predictive value and proportion of correct prediction for cardiac events within 6 months compared to creatine kinase MB.

CONCLUSIONS

Troponin T has proved to be an useful method for diagnosing myocardial damage in routine clinical use in the non-trauma emergency department.

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

BACKGROUND

A new commercially available rapid qualitative bedside immunoassay for cardiac troponin T has been developed. The aim of the study was to investigate whether this new rapid bedside cardiac troponin T assay facilitates diagnosing myocardial infarction in a pre-hospital setting.

METHODS

We evaluated the sensitivity and specificity of the new rapid bedside troponin T assay for myocardial infarction. In 68 patients with acute, central, crushing chest pain, who were strongly suspected of having myocardial infarction, the emergency doctor performed preclinically a bedside cardiac troponin T test. The results were compared with the diagnosis after admission to hospital, using the criteria of the World Health Organization.

RESULTS

The diagnosis of myocardial infarction was confirmed in 16/68 (24%) patients after admission to hospital, but only in 4/16 (25%) patients with myocardial infarction was a positive result observed preclinically with this test. The result was false positive in 1/5 patients (20%).

CONCLUSIONS

In contrast to an excellent specificity (0.98), sensitivity (0.25) of the rapid troponin T assay was poor. Thus, we conclude that this test cannot improve the distinction between myocardial infarction and angina pectoris in a pre-hospital setting.

Assessment of the patient with chest pain in the accident and emergency department

This article will review measures enabling emergency staff to identify patients with chest pain who are likely to need admission to a cardiac care unit, in particular those with manifestations of acute ischaemic heart disease--acute myocardial infarction and unstable angina. Other non-cardiac causes of chest pain will also be discussed.