Sensitive troponin I assay in early diagnosis of acute myocardial infarction

Biochemical markers in acute coronary syndrome

Owing to their higher risk for cardiac death or ischemic complications, patients with acute coronary syndrome (ACS) must be identified from other causes of chest pain. Patients with acute coronary syndrome are divided into categories based on their electrocardiogram; those with new ST-segment elevation and those who present with ST-segment depression. The subgroups of patients with ST-segment elevation are candidates for immediate reperfusion, while fibrinolysis appears harmful for those with non-ST elevation myocardial infarction. There is increasing evidence to encourage appropriate risk stratification before deciding on a management strategy (invasive or conservative) for each patient. The TIMI, GRACE or PURSUIT risk models are recommended as useful for decisions regarding therapeutic options. Cardiac biomarkers are useful additions to these clinical tools to correctly risk stratify ACS patients. Cardiac troponin is the biomarker of choice to detect myocardial necrosis and is central to the universal definition of myocardial infarction. The introduction of troponin assays with a lower limit of detection will allow for earlier diagnosis of patients who present with chest pain. Analytical and clinical validations of these new assays are currently in progress. The question is whether the lower detection limit of the troponin assays will be able to indicate myocardial ischemia in the absence of myocardial necrosis. Previous to the development of ultrasensitive cardiac troponin assays free fatty acids unbound to albumin and ischemia modified albumin were proposed as biochemical markers of ischemia. Advances in our knowledge of the pathogenesis of acute coronary thrombosis have stimulated the development of new biomarkers. Markers of left ventricular performance (N-terminal pro-brain natriuretic peptide) and inflammation (e.g. C-reactive protein) are generally recognized as risk indicators. Studies suggest that using a number of biomarkers clinicians can risk stratify patients over a broad range of short and long term cardiac events. Nevertheless, it is still under debate as to which biomarker combination is best preferred for risk prediction. This review will focus on recent practice guidelines for the management of patients with ACS as well as current advances in cardiac biomarkers, their integration into clinical care and their diagnostic, prognostic and therapeutic utility.

Comparison of prognostic value of high-sensitivity and conventional troponin T in patients with non-ST-segment elevation acute coronary syndromes

BACKGROUND

The impact of high-sensitivity troponin assays on risk stratification of patients with non-ST-segment elevation acute coronary syndromes (NSTE-ACS) is unknown.

METHODS

The study included 447 patients with NSTE-ACS. Cardiac troponin T (TnT) was measured with conventional and high-sensitivity assays, in parallel, using the same plasma sample. The primary end-point was 4-year mortality.

RESULTS

The use of cut-off of 0.014 μg/L of high-sensitivity TnT (hs-TnT) instead of 0.01 μg/L of the conventional (cTnT) increased proportion of non-ST-segment elevation myocardial infarction (NSTEMI) patients by 33% (from 201 to 268 patients). Re-classified patients from unstable angina to NSTEMI had similar 4-year mortality compared to patients with NSTEMI by both assays: 16 deaths (25.1%) among 67 re-classified patients versus 47 deaths (23.6%) among patients diagnosed with NSTEMI by both assays; odds ratio=1.03, 95% confidence interval [CI] 0.53-1.97; P=0.933). The Cox model identified hsTnT (hazard ratio=2.59, 95% CI 1.22-5.50; P=0.013 for hsTnT>0.014μg/L versus hsTnT ≤ 0.014 μg/L) as an independent correlate of 4-year mortality. hsTnT significantly improved prediction of the four-year mortality (relative integrated discrimination improvement 8.2%, P=0.005).

CONCLUSIONS

The use of hsTnT instead of cTnT increased the proportion of patients with NSTEMI among patients with NSTE-ACS and significantly improved risk stratification regarding long-term mortality.

Cardiac troponin T measured by a highly sensitive assay predicts coronary heart disease, heart failure, and mortality in the Atherosclerosis Risk in Communities Study

BACKGROUND

We evaluated whether cardiac troponin T (cTnT) measured with a new highly sensitive assay was associated with incident coronary heart disease (CHD), mortality, and hospitalization for heart failure (HF) in a general population of participants in the Atherosclerosis Risk in Communities (ARIC) Study.

METHODS AND RESULTS

Associations between increasing cTnT levels and CHD, mortality, and HF hospitalization were evaluated with Cox proportional hazards models adjusted for traditional CHD risk factors, kidney function, high-sensitivity C-reactive protein, and N-terminal pro-B-type natriuretic peptide in 9698 participants aged 54 to 74 years who at baseline were free from CHD and stroke (and HF in the HF analysis). Measurable cTnT levels (≥0.003 μg/L) were detected in 66.5% of individuals. In fully adjusted models, compared with participants with undetectable levels, those with cTnT levels in the highest category (≥0.014 μg/L; 7.4% of the ARIC population) had significantly increased risk for CHD (hazard ratio=2.29; 95% confidence interval, 1.81 to 2.89), fatal CHD (hazard ratio=7.59; 95% confidence interval, 3.78 to 15.25), total mortality (hazard ratio=3.96; 95% confidence interval, 3.21 to 4.88), and HF (hazard ratio=5.95; 95% confidence interval, 4.47 to 7.92). Even minimally elevated cTnT (≥0.003 μg/L) was associated with increased risk for mortality and HF (P<0.05). Adding cTnT to traditional risk factors improved risk prediction parameters; the improvements were similar to those with N-terminal pro-B-type natriuretic peptide and better than those with the addition of high-sensitivity C-reactive protein.

CONCLUSIONS

cTnT detectable with a highly sensitive assay was associated with incident CHD, mortality, and HF in individuals from a general population without known CHD/stroke.

Comparison of high sensitivity and contemporary troponin assays for the early detection of acute myocardial infarction in the emergency department

Background

Current guidelines define acute myocardial infarction (AMI) by the rise and/or fall of cardiac troponin with ≥1 value above the 99th percentile. Past troponin assays have been unreliable at the lower end of the range. Highly sensitive assays have therefore been developed to increase the clinical sensitivity for detection of myocardial injury.

Methods

Three hundred and thirty-two patients with chest pain suggestive of AMI were prospectively recruited between November 2006 and April 2007. Serial blood samples were analysed to compare Roche Elecsys high sensitivity troponin T (hsTnT), Abbott Architect troponin I 3rd generation (TnI 3) and Roche Elecsys troponin T (TnT) for the diagnosis of AMI.

Results

One hundred and ten (33.1%) patients were diagnosed with AMI. Test performance for the diagnosis of AMI, as quantified by receiver operating characteristic area under the curve (95% confidence intervals) for baseline/follow-up troponins were as follows: hsTnT 0.90 (0.87–0.94)/0.94 (0.91–0.97), TnI 3 0.88 (0.84–0.92)/0.93 (0.90–0.96) and TnT 0.80 (0.74–0.85)/0.89 (0.85–0.94). hsTnT was superior to TnT ( P < 0.001/0.013 at baseline/follow-up) but equivalent to TnI 3. For patients with a final diagnosis of AMI, baseline troponins were raised in more patients for hsTnT (83.6%) than TnI 3 (74.5%) and TnT (62.7%). A delta troponin of ≥20% increased the specificity of hsTnT from 80.6% to 93.7% but reduced sensitivity from 90.9% to 71.8%.

Conclusion

hsTnT was superior to TnT but equivalent to TnI 3 for the diagnosis of AMI. Serial troponin measurement increased test performance. hsTnT was the most likely to be raised at baseline in those with AMI. A delta troponin increases specificity but reduces sensitivity.

High sensitivity troponin outperforms contemporary assays in predicting major adverse cardiac events up to two years in patients with chest pain

Background

Previous studies have shown a risk of subsequent major adverse cardiovascular events (MACEs) in patients with suspected acute coronary syndromes (ACSs) and elevated cardiac troponin. The aim of this study was to compare prognostic utility of high-sensitivity troponin with contemporary troponin assays in such patients.

Methods

In total, 332 patients with suspected ACS were investigated between November 2006 and April 2007; all were followed for two years. Blood samples were analysed to compare Roche Elecsys high-sensitivity troponin T (hsTnT), Abbott Architect troponin I 3rd generation (TnI 3) and Roche Elecsys troponin T (TnT), for the prediction of MACE (composite of cardiovascular death, non-fatal myocardial infarction and revascularization).

Results

Sixty-eight patients (20.5%) experienced MACE between discharge and two years. Receiver operating characteristic (ROC) curve derived area under the ROC curve (95% confidence intervals) for baseline hsTnT were 0.70 (0.63–0.76), TnI 3 0.66 (0.59–0.73) and TnT 0.61 (0.53–0.69). hsTnT ( P = 0.001) was superior to TnT and TnI 3 trended ( P = 0.094) to superiority but were equivalent to each other. hsTnT best stratified patients with cumulative event rates for two-year MACE of 35.6% for levels ≥99th percentile, 17.9% for levels between the limit of detection (LOD) and 99th percentile and 5.4% for levels <LOD compared with TnI 3: 33.0%, 31.1% and 10.9%, respectively. TnT had MACE rates of 36.7% when ≥99th percentile and 15.4% when <99th percentile (=LOD).

Conclusions

hsTnT outperformed contemporary TnI and TnT assays for the prediction of MACE at two years. Those with levels below the LOD for hsTnT identified a group of patients at very low risk for adverse events.

Clinical assessment of chest pain and guidelines for imaging

For many emergency facilities, risk assessment of patients with diffuse chest pain still poses a major challenge. In their currently valid recommendations, the international cardiological societies have defined a standardized assessment of the prognostically relevant cardiac risk criteria. Here the classic sequence of basic cardiac diagnostics including case history (cardiac risk factors), physical examination (haemodynamic and respiratory vital parameters), ECG (ST segment analysis) and laboratory risk markers (troponin levels) is paramount. The focus is, on the one hand, on timely indication for percutaneous catheterization, especially in patients at high cardiac risk with or without ST-segment elevation in the ECG, and, on the other hand, on the possibility of safely discharging patients with intermediate or low cardiac risk after non-invasive exclusion of a coronary syndrome. For patients in the intermediate or low risk group, physical or pharmacological stress testing in combination with scintigraphy, echocardiography or magnetic resonance imaging is recommended in addition to basic diagnostics. Moreover, the importance of non-invasive coronary imaging, primarily cardiac CT angiography (CCTA), is increasing. Current data show that in intermediate or low risk patients this method is suitable to reliably rule out coronary heart disease. In addition, attention is paid to the major differential diagnoses of acute coronary syndrome, particularly pulmonary embolism and aortic dissection. Here the diagnostic method of choice is thoracic CT, possibly also in combination with CCTA aiming at a triple rule-out.

Troponin I and C-reactive protein are commonly detected in patients with breast cancer treated with dose-dense chemotherapy incorporating trastuzumab and lapatinib

PURPOSE

There are no validated methods of early detection of cardiotoxicity from trastuzumab (T) following anthracycline-based chemotherapy. Currently changes in left ventricular ejection fraction (LVEF) are assessed but this approach has limited sensitivity and specificity. Within a prospective feasibility study of dose-dense (dd) doxorubicin and cyclophosphamide (AC) → weekly paclitaxel (P) with T and lapatinib (L), we included a preplanned analysis of correlative cardiac Troponin I (cTnI) and C-reactive protein (CRP) as early biomarkers of cardiotoxicity.

EXPERIMENTAL DESIGN

As previously described, patients received ddACx 4 → PTL → TL. LVEF was assessed at months 0, 2, 6, 9, and 18 and cTnI and CRP measured every 2 weeks during chemotherapy then at months 6, 9, and 18. These biomarkers were correlated with changes in LVEF.

RESULTS

Ninety-five patients enrolled. Overall, 3 (3%) patients withdrew during AC and 41 (43%) withdrew during PTL → TL, mostly due to diarrhea. Median LVEF was 68% (baseline), 69% (month 2), 65% (month 6), 65% (month 9), and 65% (month 18). The majority (67%) had a detectable cTnI during the study. The proportion of detectable cTnIs increased over time; 4% at baseline, 11% at month 2, and 50% at month 3. The timing of these detectable cTnIs preceded maximum-recorded decline in LVEF. However, overall, maximum cTnI levels did not correlate with LVEF declines. A detectable CRP was seen in 74/95 (78%) but did not correlate with LVEF declines.

CONCLUSION

In patients receiving ddAC → PTL, cTnIs are commonly detected. These elevations may precede changes in LVEF but, as assessed in this trial, do not predict CHF.

Rapid detection of myocardial infarction with a sensitive troponin test

Rapid identification and treatment of patients with a myocardial infarction (MI) is mandatory. We studied the diagnostic capacities of a sensitive troponin assay for detection of MI in emergency department patients within 2 hours after arrival. The study included 157 patients suspected of having non-ST-elevation acute coronary syndrome. Blood was drawn on arrival (T0) and 2 (T2), 6, and 12 hours later. At T2, a troponin concentration above the MI cutoff is 87% sensitive and 100% specific for MI detection (positive predictive value [PPV], 100%; negative predictive value [NPV], 96%). If a difference of more than 30% between the troponin measurements at T0 and T2 in the absence of an absolute troponin increase above the 99th percentile of a reference population is also considered indicative of MI, the sensitivity increases to 100% and specificity decreases to 87% (PPV, 70%; NPV, 100%). Sensitivity and specificity of creatine kinase-MB and myoglobin are lower than those of troponin. By using a sensitive troponin assay and simple algorithms, the diagnosis of MI can be determined within 2 hours after arrival at the emergency department. Measurement of myoglobin and creatine kinase-MB has no added value.

Elevated Soluble fms-Like Tyrosine Kinase-1 Levels in Acute Coronary Occlusion

Objective—

Early recognition of an acute coronary occlusion (ACO) improves clinical outcomes. Soluble fms-like tyrosine kinase-1 (sFLT1) is an endothelium-derived protein induced by hypoxia. We tested whether sFLT1 levels are elevated in ACO.

Methods and Results—

Serum sFLT1 levels were measured by enzyme-linked immunosorbent assay in patients with ST-segment elevations and angiographically confirmed ACO, unstable angina/non ST-segment elevation myocardial infarction, and 2 control groups. To further explore sFLT1 release, a mouse model of ACO and in vitro human coronary artery endothelial cell injury were used. sFLT1 levels were increased in ACO compared with unstable angina/non-ST-elevation myocardial infarction, catheterized controls, or healthy volunteers (200.7±15.5 versus 70.7±44.0 versus 10.2±4.0 versus 11.7±1.7 pg/mL respectively, P <0.001 versus ACO). At presentation, all ACO patients had elevated sFLT1 levels (>15 pg/mL, 99th percentile in controls), whereas 57% had levels of the MB isoform of creatine kinase levels >10 ng/mL ( P <0.01) and 85% had ultrasensitive troponin I levels >0.05 ng/mL ( P <0.05). Within 60 minutes after symptom onset, sFLT1 was more sensitive than the MB isoform of creatine kinase or ultrasensitive troponin I for ACO (100% versus 20% versus 20% respectively; P ≤0.01 for each). Within 60 minutes of ACO in mice, sFLT1 levels were elevated. Hypoxia and thrombin increased sFLT1 levels within 15 minutes in human coronary artery endothelial cells.

Conclusion—

sFLT1 levels may be an early indicator of endothelial hypoxia in ACO.

[Acute coronary syndrome. A diffuse diagnosis]

Acute coronary syndrome is one of the most common reasons for a presentation in an emergency room. The biggest component of the overall mortality in adults is acute coronary syndrome or in this context its complications. The term "acute coronary syndrome" comprises on one hand 3 entities--unstable angina pectoris, Non-ST-elevation myocardial infarction and ST-elevation myocardial infarction. On the other hand particularly in emergency medicine the term is used as a working diagnosis for patients with unclear, acute chest pain. Although the underlying disease has not changed, especially with the introduction of troponins and the changes of their reference values the concept and importance of acute myocardial infarction has changed. This article emphasises on the current nomenclature and its importance for the adequate diagnosis and treatment are explained.

Pregnancy-associated plasma protein A values in patients with stable cardiovascular disease: use of a new monoclonal antibody-based assay

BACKGROUND

PAPP-A is promising in improving risk stratification and invasive treatment decisions in stable cardiovascular patients. We evaluated the prognostic value of pregnancy-associated plasma protein A (PAPP-A) measured by a novel assay in stable cardiovascular patients.

METHODS

We investigated 228 stable cardiovascular outpatients. Blood was drawn for PAPP-A measurement after echocardiography and ergometry prior to heart catheterization. Angiographically we determined severity as well as qualitative characteristics suspect for vulnerability of coronary lesions. After 1108±297 days, follow-up information was obtained by questionnaire mailings and interviews by phone.

RESULTS

104 patients had coronary stenosis≥70%, 75 had B-type lesions≥50%, 46 showed complex lesions, and 68 were suspected to have vulnerable lesions. Median PAPP-A was 1.76 (interquartile range 1.21, 2.63) μIU/ml in the entire cohort. PAPP-A concentrations did not differ in dependence on coronary artery findings. A cutpoint of 2.7 μIU/ml was derived from receiver-operator characteristics for outcome measures. For this cutoff, Cox proportional hazard models with 19 further clinical variables showed that PAPP-A was predictive for all-cause death (HR 4.73, 95% CI 1.46-15.31, p=0.01), all-cause death or nonfatal infarction (HR 4.01, 95% CI 1.58-10.13, p=0.003) and all-cause death, nonfatal myocardial infarction or hospitalization (HR 1.96, 95% CI 1.03-3.70, p=0.04). The predictive value of PAPP-A did not change substantially after correction for values of cardiac troponin, using a highly sensitive cardiac troponin I research assay.

CONCLUSIONS

PAPP-A, measured by a new, monoclonal antibody-based assay is a promising prognostic marker in patients with stable cardiovascular disease and an indication for heart catheterization.

Multicenter analytical evaluation of a high-sensitivity troponin T assay

BACKGROUND

High-sensitivity cardiac troponin assays are being introduced clinically for earlier diagnosis of acute myocardial infarction (AMI). We evaluated the analytical performance of a high-sensitivity cardiac troponin T assay (hscTnT, Roche Diagnostics) in a multicenter, international trial.

METHODS

Three US and 5 European sites evaluated hscTnT on the Modular® Analytics E170, cobas® 6000, Elecsys 2010, and cobas® e 411. Precision, accuracy, reportable range, an inter-laboratory comparison trial, and the 99th percentile of a reference population were assessed.

RESULTS

Total imprecision (CVs) were 4.6-36.8% between 3.4 and 10.3 ng/L hscTnT. Assay linearity was up to 10,000 ng/L and the limit of blank and detection were 3 and 5 ng/L, respectively. The 99th percentile reference limit was 14.2 ng/L (n=533). No significant differences between specimen types, assay incubation time, or reagent lots existed. A substantial positive bias (76%) exists between the 4th generation and hscTnT assays at the low end of the measuring range (<50 ng/L). hscTnT serum pool concentrations were within 2SD limits of the mean of means in the comparison trial, indicating comparable results across multiple platforms and laboratories.

CONCLUSION

The Roche hscTnT assay conforms to guideline precision requirements and will likely identify additional patients with myocardial injury suspicious for AMI.

Prognostic value of sensitive troponin T in patients with stable and unstable angina and undetectable conventional troponin

BACKGROUND

high-sensitivity cardiac troponin assays enable the measurement of cardiac troponin concentrations in the majority of patients with coronary artery disease. The objective of this study was to investigate the prognostic value of sensitive cardiac troponin in patients with stable and unstable angina presenting with undetectable levels of conventional troponin.

METHODS

this study included 1,057 patients with stable (808 patients) or unstable (249 patients) angina who presented with undetectable conventional cardiac troponin T and underwent coronary artery revascularization. The cardiac troponin T was measured with conventional and high-sensitivity assays, in parallel, using the same plasma sample. The primary end point was 4-year mortality.

RESULTS

the total sensitive troponin T level (median [interquartile range]) was 0.008 (0.005-0.014) microg/L. Variables independently associated with an elevated level of sensitive troponin T were elderly age, male sex, higher body mass index, presence of diabetes, unstable angina, increased New York Heart Association class, reduced left ventricular ejection fraction, elevated level of N-terminal pro-brain natriuretic peptide, reduced glomerular filtration rate, and elevated level of C-reactive protein. During the follow-up period, there were 83 deaths. The sensitive troponin T level was an independent predictor of 4-year mortality (adjusted hazard ratio = 1.47 with 95% CI 1.17-1.84, P < .001 for each unit increase in the natural logarithm of the sensitive troponin T).

CONCLUSIONS

the elevated levels of sensitive cardiac troponin T in patients with stable or unstable angina presenting with undetectable conventional cardiac troponin T are significantly associated with reduced survival.

High-sensitivity troponin assays in the evaluation of patients with acute chest pain in the emergency department

Evaluating patients with acute chest pain presenting to the emergency department remains an ongoing challenge. The spectrum of etiologies in acute chest pain ranges from minor disease entities to life-threatening diseases, such as pulmonary embolism, acute aortic dissection or acute myocardial infarction (MI). The diagnosis of acute MI is usually made integrating the triad of patient history and clinical presentation, readings of 12-lead ECG and measurement of cardiac troponins (cTn). Introduction of high-sensitivity cTn assays substantially increases sensitivity to identify patients with acute MI even at the time of presentation to the emergency department at the cost of specificity. However, the proportion of patients presenting with cTn positive, non-vascular cardiac chest pain triples with the implementation of new sensitive cTn assays increasing the difficulty for the emergency physician to identify those patients who are at need for invasive diagnostics. The main objectives of this mini-review are 1) to discuss elements of disposition decision made by the emergency physician for the evaluation of chest pain patients, 2) to summarize recent advances in assay technology and relate these findings into the clinical context, and 3) to discuss possible consequences for the clinical work and suggest an algorithm for the clinical evaluation of chest pain patients in the emergency department.

The value of N-terminal proB-type natriuretic peptide for early identification of myocardial infarction in patients with high-risk non-ST-elevation acute coronary syndromes

N-terminal proB-type natriuretic peptide (NT-proBNP) is a marker of biomechanical strain, secreted by cardiomyocytes in response to ischemia. As necrosis occurs after prolonged ischemia, a rise in NT-proBNP concentration could precede a rise in markers of necrosis.

The aim of the study was to evaluate whether NT-proBNP is able to identify those patients with an evolving myocardial infarction (MI) with high-risk non-ST-elevation acute coronary syndromes (NSTE-ACS). Data were analyzed from a prospective cohort of 103 high-risk NSTE-ACS patients admitted within 6 h after onset of pain and treated with an early invasive strategy. NT-proBNP samples, obtained immediately upon admission, were related to the presence of an in hospital MI. The optimal cut-off value for NT-proBNP was determined using receiver-operating characteristics (ROC) curve analysis.

Analyses was performed separately for creatinine kinase MB-mass (CKMB) and troponin T (TnT) based MI definitions. In both cases, a NT-proBNP concentration above 40 pmol/L (339 ng/L) at admission proved to be independently associated with the presence of MI. The diagnostic odds ratio (OR) for CKMB-MI was 4.9 (confidence interval 2.0–11.9, p<0.001). The diagnostic OR for TnT-MI was 4.9 (1.8–14.4, p=0.003). Adjusting for differences in baseline variables did not weaken the diagnostic OR. In addition, elevated NT-proBNP concentrations were related to unfavour-able demographic, physical and biochemical parameters.

With a dichotomous cut-off value, a single elevated NT-proBNP (>40 pmol/L) at admission provides independent information about the presence of MI in high-risk NSTE-ACS patients.

Treatment and outcomes of first troponin-negative non-ST-segment elevation myocardial infarction

Little is known about non-ST-segment elevation myocardial infarction (MI) in patients with an initial negative troponin finding. The aim of this study was to determine in post hoc analysis of a large regional medical center presenting clinical characteristics, treatment differences, and in-hospital and 6-month outcomes of first troponin-negative MI (FTNMI). In this study, 659 of 1,855 consecutive patients with non-ST-segment elevation MI (35.5%) were classified as having FTNMI. In-hospital cardiac catheterization rates were similar between the 2 groups (70.1% vs 71.5%, p = 0.53) In hospital, patients with FTNMI were less likely to receive statins (48.9% vs 59.9%, p <0.001). On discharge, patients with FTNMI were less likely to be on clopidogrel (53.1% vs 59.0%, p = 0.019) and statins (67.7% vs 75.2%, p <0.001). At 6-month follow-up, patients with FTNMI were less likely to be on clopidogrel (43.5% vs 55.2%, p = 0.01) In-hospital recurrent ischemia was 2 times as common in FTNMI (20.1% vs 11.5%, p <0.001). There were no differences, however, in congestive heart failure, cardiogenic shock, cardiac arrest, stroke, or death in hospital. At 6 months, patients with FTNMI were 2 times as likely to have had recurrent MI (12.0% vs 6.6%, p <0.001). Combined end points of death at 6 months, MI, stroke, and rehospitalization were higher for FTNMI (47.7% vs 40.9%, p = 0.017); however, this was due to higher rates of recurrent MI. In conclusion, patients with FTNMI received less aggressive pharmacotherapy and were 2 times as likely to have recurrent MI at 6 months. FTNMI is common and represents a clinical entity that should be treated more aggressively.

Predictors of cardiovascular events after liver transplantation: a role for pretransplant serum troponin levels

Cardiovascular complications are major causes of morbidity and mortality after liver transplantation. Identifying candidates at highest risk of postoperative complications is a cornerstone of optimizing outcomes and utility. Using traditional cardiac risk factors in addition to C-reactive protein (CRP) levels, troponin levels, and echocardiographic parameters before transplantation, we sought to define cardiac risk so that we could predict cardiovascular events after transplantation. From December 1998 to December 2001, 230 adult patients who underwent liver transplantation with a median follow-up of 8.2 years were studied. The risk factors for cardiac disease were as follows: male gender with a mean age of approximately 50 years (57%), smoking history (60%), diabetes (23%), hypertension (19%), elevated troponin (25%), elevated CRP (25%), and preexisting cardiac disease (16%). Fifty-nine cardiac events occurred over 8.2 years. Risk factors (univariate analysis) for first cardiac events included age in decades [hazard ratio (HR) = 1.31, P = 0.047], diabetes (HR = 2.20, P = 0.004), prior cardiovascular disease (HR = 4.77, P < 0.0001), a troponin I level > 0.07 ng/mL (HR = 2.00, P = 0.023), left ventricular hypertrophy (HR = 2.06, P = 0.047), stress wall abnormalities (HR = 2.25, P = 0.018), and ischemia on stress imaging (HR = 2.89, P = 0.015). Multivariate analysis confirmed age, diabetes, a troponin I level > 0.07, and prior cardiac disease as independent risk factors for posttransplant cardiac events. In conclusion, pretransplant elevated troponin levels, diabetes, and a history of cardiovascular disease, alone or in combination, are strongly associated with the occurrence of posttransplant cardiovascular events.

Troponin elevation in coronary vs. non-coronary disease

Acute myocardial infarction is defined as myocardial cell death due to prolonged myocardial ischaemia. Cardiac troponins (cTn) are the most sensitive and specific biochemical markers of myocardial injury and with the new high-sensitivity troponin methods very minor damages on the heart muscle can be detected. However, elevated cTn levels indicate cardiac injury, but do not define the cause of the injury. Thus, cTn elevations are common in many disease states and do not necessarily indicate the presence of a thrombotic acute coronary syndrome (ACS). In the clinical work it may be difficult to interpret dynamic changes of troponin in conditions such as stroke, pulmonary embolism, sepsis, acute perimyocarditis, Tako-tsubo, acute heart failure, and tachycardia. There are no guidelines to treat patients with elevated cTn levels and no coronary disease. The current strategy of treatment of patients with elevated troponin and non-acute coronary syndrome involves treating the underlying causes. The aim of this paper is to review data from studies of non-ACS patients with acutely elevated troponin who in clinical practice may be difficult to discriminate from ACS patients.

Association of troponin T detected with a highly sensitive assay and cardiac structure and mortality risk in the general population

CONTEXT

Detectable levels of cardiac troponin T (cTnT) are strongly associated with structural heart disease and increased risk of death and adverse cardiovascular events; however, cTnT is rarely detectable in the general population using standard assays.

OBJECTIVES

To determine the prevalence and determinants of detectable cTnT in the population using a new highly sensitive assay and to assess whether cTnT levels measured with the new assay associate with pathological cardiac phenotypes and subsequent mortality.

DESIGN, SETTING, AND PARTICIPANTS

Cardiac troponin T levels were measured using both the standard and the highly sensitive assays in 3546 individuals aged 30 to 65 years enrolled between 2000 and 2002 in the Dallas Heart Study, a multiethnic, population-based cohort study. Mortality follow-up was complete through 2007. Participants were placed into 5 categories based on cTnT levels.

MAIN OUTCOME MEASURES

Magnetic resonance imaging measurements of cardiac structure and function and mortality through a median of 6.4 (interquartile range, 6.0-6.8) years of follow-up.

RESULTS

In Dallas County, the prevalence of detectable cTnT (≥0.003 ng/mL) was 25.0% (95% confidence interval [CI], 22.7%-27.4%) with the highly sensitive assay vs 0.7% (95% CI, 0.3%-1.1%) with the standard assay. Prevalence was 37.1% (95% CI, 33.3%-41.0%) in men vs 12.9% (95% CI, 10.6%-15.2%) in women and 14.0% (95% CI, 11.2%-16.9%) in participants younger than 40 years vs 57.6% (95% CI, 47.0%-68.2%) in those 60 years and older. Prevalence of left ventricular hypertrophy increased from 7.5% (95% CI, 6.4%-8.8%) in the lowest cTnT category (<0.003 ng/mL) to 48.1% (95% CI, 36.7%-59.6%) in the highest (≥0.014 ng/mL) (P < .001); prevalence of left ventricular systolic dysfunction and chronic kidney disease also increased across categories (P < .001 for each). During a median follow-up of 6.4 years, there were 151 total deaths, including 62 cardiovascular disease deaths. All-cause mortality increased from 1.9% (95% CI, 1.5%-2.6%) to 28.4% (95% CI, 21.0%-37.8%) across higher cTnT categories (P < .001). After adjustment for traditional risk factors, C-reactive protein level, chronic kidney disease, and N-terminal pro-brain-type natriuretic peptide level, cTnT category remained independently associated with all-cause mortality (adjusted hazard ratio, 2.8 [95% CI, 1.4-5.2] in the highest category). Adding cTnT categories to the fully adjusted mortality model modestly improved model fit (P = .02) and the integrated discrimination index (0.010 [95% CI, 0.002-0.018]; P = .01).

CONCLUSION

In this population-based cohort, cTnT detected with a highly sensitive assay was associated with structural heart disease and subsequent risk for all-cause mortality.

Implementation of high sensitivity cardiac troponin T measurement in the emergency department

BACKGROUND

we examined the diagnostic performance of high sensitivity cardiac troponin T (cTnThs) measurement and its ability to predict risk in unselected patients presenting to the emergency department with acute chest pain.

METHODS

we conducted a retrospective analysis of 137 consecutive patients with chest pain (age range, 66 ± 16 years; 64% male). A final diagnosis of acute myocardial infarction was made using the "old" (cTnT fourth-generation assay, ≥ 0.04 microg/L) or the "new" cutpoint (cTnThs ≥ 0.014 microg/L).

RESULTS

the adjudicated final diagnosis of acute myocardial infarction significantly increased from 20 to 35 patients (a 75% increase) and troponin-positive nonvascular cardiac chest pain from 10 to 30 (a 200% increase) using cTnThs. The number of patients with unstable angina or troponin-negative nonvascular cardiac chest pain significantly decreased (P <.05). Diagnostic performance of cTnThs levels at admission was significantly higher compared to cTnT levels (area under the curve [AUC] 0.85 vs AUC 0.70; P <.05). cTnThs levels below the detection limit (<0.003 microg/L) had a negative predictive value of 100% to exclude acute myocardial infarction. The event rate during 6 months of follow-up was low in patients with cTnThs levels <0.014 microg/L, while patients with cTnT levels ≥ 0.04 μg/L were at increased, and patients with cTnThs ≥ 0.014 μg/L and cTnT <0.04 microg/L at intermediate risk of death or recurrent myocardial infarction (P = .002). Risk was highest in chest pain patients with dynamic changes of cTnThs levels >30%.

CONCLUSION

the introduction of cTnThs assay displays an excellent diagnostic performance for the workup of patients with chest pain at the time of their initial presentation. Even small increases of cTnThs indicate increased risk for death or myocardial infarction during follow-up.

Probabilistic Bayesian reasoning can help identifying potentially wrong immunoassays results in clinical practice: even when they appear ‘not-unreasonable’

Background

Immunoassays are susceptible to analytical interferences including from endogenous immunoglobulin antibodies at a rate of ∼0.4% to 4%. Hundreds of millions of immunoassay tests (>10 millions in the UK alone) are performed yearly worldwide for measurements of an array of large and small moieties such as proteins, hormones, tumour markers, rheumatoid factor, troponin, small peptides, steroids and drugs.

Methods

Interference in these tests can lead to false results which when suspected, or surmised, can be analytically confirmed in most cases. Suspecting false laboratory data in the first place is not difficult when results are gross and without clinical correlates. However, when false results are subtle and/or plausible, it can be difficult to suspect with adverse clinical sequelae. This problem can be ameliorated by using a probabilistic Bayesian reasoning to flag up potentially suspect results even when laboratory data appear “not-unreasonable”.

Results

Essentially, in disorders with low prevalence, the majority of positive results caused by analytical interference are likely to be false positives. On the other hand, when the disease prevalence is high, false negative results increase and become more significant. To illustrate the scope and utility of this approach, six different examples covering wide range of analytes are given, each highlighting specific aspect/nature of interference and suggested options to reduce it.

Conclusion

Bayesian reasoning would allow laboratorians and/or clinicians to extract information about potentially false results, thus seeking follow-up confirmatory tests prior to the initiation of more expensive/invasive procedures or concluding a potentially wrong diagnosis.

Early and late outcome prediction of death in the emergency room setting by point-of-care and laboratory assays of cardiac troponin I

BACKGROUND

Point-of-care (POC) assays of cardiac troponins are common in the emergency department setting. The question raised was as follows: What is the clinical impact of the results of POC assays of cardiac troponins as compared with sensitive laboratory assays?

METHODS

Patients admitted consecutively to the emergency department (N = 1,069) and on whom cardiac troponins were requested as part of their clinical work-up were included. Cardiac troponin I (cTnI) was measured by the POC assays-i-Stat (Abbott Diagnostics, Abbott Park, IL) and Stratus CS (Siemens Healthcare Diagnostics, Deerfield, IL)-and by the laboratory assays-Access AccuTnI (Beckman Coulter, Fullerton, CA) and Architect cTnI (Abbott Diagnostics). Results were related to early (14 days) and late outcome (median 3.3 months, range 0.1-35) as to death.

RESULTS

The laboratory assays identified more patients (P < .001) with elevated levels than the two POC assays (39%-74% vs 20%-27%). Adopting the 99th percentiles upper reference limit, the Access AccuTnI identified 88% and Architect cTnI identified 81% of all patients who died of cardiovascular disease as compared with 50% and 54% for i-Stat and Stratus CS, respectively (P < .001). Negative predictive values for the laboratory assays were 97% as compared with 89% to 93% for the POC assays. Negative likelihood ratios were 0.25 (CI 0.15-0.041) and 0.59 to 0.68 (CI 0.47-0.79), respectively.

CONCLUSIONS

The current POC cTnI assays are less sensitive for outcome prediction of patients with myocardial injury. The clinical judgment of the patient with suspected myocardial ischemia should not solely rely on results from POC assays. If a clinical suspicion of myocardial injury remains despite negative cTnI results with the POC assays, such results should be complemented by results from sensitive laboratory assays.

Testing of low-risk patients presenting to the emergency department with chest pain: a scientific statement from the American Heart Association

The management of low-risk patients presenting to emergency departments is a common and challenging clinical problem entailing 8 million emergency department visits annually. Although a majority of these patients do not have a life-threatening condition, the clinician must distinguish between those who require urgent treatment of a serious problem and those with more benign entities who do not require admission. Inadvertent discharge of patients with acute coronary syndrome from the emergency department is associated with increased mortality and liability, whereas inappropriate admission of patients without serious disease is neither indicated nor cost-effective. Clinical judgment and basic clinical tools (history, physical examination, and electrocardiogram) remain primary in meeting this challenge and affording early identification of low-risk patients with chest pain. Additionally, established and newer diagnostic methods have extended clinicians' diagnostic capacity in this setting. Low-risk patients presenting with chest pain are increasingly managed in chest pain units in which accelerated diagnostic protocols are performed, comprising serial electrocardiograms and cardiac injury markers to exclude acute coronary syndrome. Patients with negative findings usually complete the accelerated diagnostic protocol with a confirmatory test to exclude ischemia. This is typically an exercise treadmill test or a cardiac imaging study if the exercise treadmill test is not applicable. Rest myocardial perfusion imaging has assumed an important role in this setting. Computed tomography coronary angiography has also shown promise in this setting. A negative accelerated diagnostic protocol evaluation allows discharge, whereas patients with positive findings are admitted. This approach has been found to be safe, accurate, and cost-effective in low-risk patients presenting with chest pain.

The clinical significance of cardiac troponins in medical practice

Troponins are regulatory proteins that form the cornerstone of muscle contraction. The amino acid sequences of cardiac troponins differentiate them from that of skeletal muscles, allowing for the development of monoclonal antibody-based assay of troponin I (TnI) and troponin T (TnT). Along with the patient history, physical examination and electrocardiography, the measurement of highly sensitive and specific cardiac troponin has supplanted the former gold standard biomarker (creatine kinase-MB) to detect myocardial damage and estimate the prognosis of patients with ischemic heart disease. The current guidelines for the diagnosis of non-ST segment elevation myocardial infarction are largely based on an elevated troponin level. The implementation of these new guidelines in clinical practice has led to a substantial increase in the frequency of myocardial infarction diagnosis. Automated assays using cardiac-specific monoclonal antibodies to cardiac TnI and TnT are commercially available. They play a major role in the evaluation of myocardial injury and prediction of cardiovascular outcome in cardiac and non-cardiac causes. In this review we discuss the clinical applications of cardiac troponins and the interpretation of elevated levels in the context of various clinical settings.

Can low serum levels of S100B predict normal CT findings after minor head injury in adults?: an evidence-based review and meta-analysis

OBJECTIVE

To determine whether low levels of S100B in serum can predict normal computed tomography (CT) findings after minor head injury (MHI) in adults.

PARTICIPANTS

Not applicable.

DESIGN

Systematic evidence-based review of the peer-reviewed literature with meta-analytical interpretation.

PRIMARY MEASURES

Not applicable.

RESULTS

We identified 12 eligible articles that specifically studied adult MHI patients with S100B and cranial CT scans in the acute phase after injury, comprising a total of 2466 separate patients. Individual negative predictive values of 90% to 100% were found for the ability of a negative (under cutoff) S100B level to predict a normal CT scan. A total of 6 patients included in the studies had low S100B levels and positive CT scans (0.26%) and only 1 of these patients (0.04%) had a clinically relevant CT finding. The pooled negative predictive value for all studies was more than 99% (95% CI 98%-100%), with an average prevalence for any CT finding at 8%. The studies are consistently classed as level 2 and level 3 grades of evidence, suggesting a grade B recommendation.

CONCLUSION

Low serum S100B levels accurately predict normal CT findings after MHI in adults. S100B sampling should be considered in MHI patients with no focal neurological deficit, an absence of significant extracerebral injury, should be taken within 3 hours of injury, and the cutoff for omitting CT set at less than 0.10 microg/L. Care givers should also be aware of other clinical factors predictive of intracranial complications after MHI.

Assessment of disease severity and outcome in patients with systemic light-chain amyloidosis by the high-sensitivity troponin T assay

Cardiac biomarkers provide prognostic information in light-chain amyloidosis (AL). Thus, a novel high-sensitivity cardiac troponin T (hs-TnT) assay may improve risk stratification. hs-TnT was assessed in 163 patients. Blood levels were higher with cardiac than renal or other organ involvement and were related to the severity of cardiac involvement. Increased sensitivity was not associated with survival benefit. Forty-seven patients died during follow-up (22.3 ± 1.0 months). Nonsurvivors had higher hs-TnT than survivors. Outcome was worse if hs-TnT more than or equal to 50 ng/L and best less than 3 ng/L. Survival of patients with hs-TnT 3 to 14 ng/L did not differ from patients with moderately increased hs-TnT (14-50 ng/L), but was worse if interventricular septum was more than or equal to 15 mm. Discrimination according to the Mayo staging system was only achieved by the use of the hs-TnT assay, but not by the fourth-generation troponin T assay. Multivariate analysis revealed hs-TnT, NT-proBNP, and left ventricular impairment as independent risk factors for survival. hs-TnT and NT-proBNP predicted survival, even after exclusion of patients with impaired renal function. Plasma levels of the hs-TnT assay are associated with the clinical, morphologic, and functional severity of cardiac AL amyloidosis and could provide useful information for clinicians on cardiac involvement and outcome.

Diagnostic and Prognostic Information Provided by a High Sensitivity Assay for Cardiac Troponin T

Cardiac troponins (cTns) are the preferred biomarkers for the diagnosis of acute myocardial infarction, assessment of risk and prognosis, and for determination of antithrombotic and revascularization strategy in patients with acute coronary syndromes. The implementation of high sensitivity cTn assays into the clinical routine has increased the number of patients diagnosed with myocardial infarction. In addition, the number of patients with elevated cTn levels that cannot be explained by acute ischemic injury was increased, which is observed in patients with chronic heart disease and other nonischemic cardiac injury or in patients with impaired renal function. The new definition of myocardial infarction provides support for the interpretation of elevated cTn measured with high sensitivity cTn assays in patients with suspected acute coronary syndrome. This review will summarize clinical studies with the recently introduced high sensitivity cTnT assay (TnT hs) with reference to recent experience with high sensitivity cTn assays in general.

Sensitive Cardiac Troponin Assays: Myth and Magic or a Practical Way Forward?

Cardiac troponins (cTn) are considered to be the ‘gold standard’ biomarkers for the diagnosis of acute coronary syndrome (ACS) a pathological spectrum which includes cardiac ischemia, angina, myocardial infarction and ultimately cardiac failure. The growing evidence base for the diagnostic and prognostic use of cTn in ACS has resulted in a universal redefinition of acute myocardial infarction (AMI). A diagnosis of AMI includes the detection of an elevated cTn (or CK-MB) with at least one measurement within 24 hours of the cardiac episode being >upper 99th percentile of a reference population, in conjunction with evidence of myocardial ischemia. A number of high sensitivity immunoassays with claims of superior imprecision and a definable 99th percentile have been produced. Clinically, these have two important impacts. First, there is a drive to change the values into whole numbers by the application of a unit change which carries the scope for confusion. Secondly, the near-normal Gaussian distribution of sensitive cTn in healthy subjects will increase the frequency of cTn positivity in the non-ACS population. The problem is to decipher if such minor elevations in cTn are of clinical concern. What is certain is that AMI remains a clinical not a biochemical diagnosis and the interpretation of cTn concentrations should be made according to the clinical context.

Novel biomarkers in cardiovascular disease: update 2010

The rapid evaluation of patients presenting with symptoms suggestive of an acute coronary syndrome is of great clinical relevance. Biomarkers have become increasingly important in this setting to supplement electrocardiographic findings and patient history because one or both can be misleading. Today, cardiac troponin is still the only marker used routinely in this setting due to its myocardial tissue specificity and sensitivity, as well as its established usefulness for therapeutic decision making. However, even current generation troponin assays have certain limitations such as insufficient sensitivity for diagnosing unstable angina. Novel high-sensitivity assays for cardiac troponin have the potential to overcome these limitations. Further studies are needed to answer some critical questions regarding the best cutoffs for diagnosis and risk assessment and the optimal work-up for rule-out of acute myocardial infarction. Other nonmyocardial tissue-specific markers might help in this setting. Myeloperoxidase, copeptin, and growth differentiation factor 15 reflect different aspects of the development of atherosclerosis or acute ischemia. Each has demonstrated impact in risk stratification of acute coronary syndromes. Limited data also show that copeptin may, when used together with cardiac troponin, improve the sensitivity for diagnosing acute myocardial infarction, and growth differentiation factor 15 may help in selection of patients that benefit from invasive therapy. Further evaluation is needed before these markers can be adopted routinely in clinical practice.