Making sense of high sensitivity troponin assays and their role in clinical care

Incidentally Raised Cardiac Troponin I Has a Worse Prognosis in Older Patients Compared to Those with Normal Cardiac Troponin I and Patients with Acute Coronary Syndrome: A Cohort Study

BACKGROUND

Incidentally elevated cardiac troponin I (cTnI) levels are common in acutely unwell older patients. However, little is known about how this impacts on the prognosis of these patients.

OBJECTIVE

We aimed to investigate whether incidentally elevated cTnI levels (group 1) are associated with poorer outcome when compared to age- and sex-matched patients without an elevated cTnI level (group 2), and to patients diagnosed with acute coronary syndrome (group 3).

PATIENTS AND METHODS

This prospective, matched cohort study placed patients ≥75 years old who were admitted to a University teaching hospital into groups 1-3, based on the cTnI levels and underlying diagnosis. Outcomes were compared between the groups using mixed-effects regression models and adjusted for renal function and C-reactive protein. All-cause mortality at discharge, at 1 month and 3 months, alongside the length of hospital stay (LOS), were recorded.

RESULTS

In total, 315 patients were included, with 105 patients in each of the 3 groups. The mean age was 84.8 ± 5.5 years, with 41.9% males. All patients were followed up for 3 months. The percent all-cause mortality at discharge and the LOS for groups 1, 2 and 3 were 12.4, 3.8 and 8.6% and 11.2, 8.5 and 7.7 days, respectively. Group 1 had significantly increased mortality at 3 months [odds ratio (OR) 2.80, 95% confidence interval (CI) 1.12-6.96; p = 0.040] and LOS (OR 1.39, 95% CI 1.08-1.79; p = 0.008) compared to group 2 and did not differ significantly when compared to 3-month mortality (OR 2.39, 95% CI 0.91-6.29; p = 0.079) or LOS (OR 1.26, 95% CI 0.96-1.66; p = 0.097) in group 3.

CONCLUSION

There is a significant association between an incidental rise in cTnI level with mortality and LOS in older patients. Further research is required to evaluate whether a more systematic management of these patients would improve the prognosis.

Clinical impact of a high-sensitivity troponin assay introduction on patients presenting to the emergency department

OBJECTIVE

Biomarkers are a critical component in the investigation of patients with potential ischaemic heart disease. The proposed benefits of a high-sensitivity troponin (hs-Tn) assay include earlier diagnosis of myocardial infarction. However, the decreased specificity may adversely affect clinical practice. The present study aims to investigate the impact that the introduction of a hs-Tn assay had on patients presenting to the ED.

METHODS

A pre- and post-interventional analysis was performed on all patients presenting to the Royal Melbourne Hospital ED, and had a troponin, in the 12 months before and after the introduction of the hs-Tn assay. The main outcome measures were ED length of stay, admission rates, proportion of patients undergoing interventional cardiac procedures and proportion diagnosed with myocardial infarction.

RESULTS

There were 6557 patients who had a conventional assay and 7335 patients who had a hs-Tn assay. The introduction of a hs-Tn assay was associated with an increased abnormal troponin rate (23.4% vs 28.1%, P < 0.001). The median length of ED stay decreased by 9.1% (P < 0.001). The proportion admitted to hospital increased (60.9% vs 65.9%, P < 0.001); however, there was no difference in the proportion undergoing revascularisation or the proportion diagnosed with myocardial infarction.

CONCLUSIONS

Although the introduction of a hs-Tn assay led to an increase in hospital admissions, the unchanged rate of cardiac procedures or final diagnoses of acute myocardial infarction and ischaemic heart disease suggests that the hs-Tn did not improve the detection of these conditions. It remains unclear whether there was a benefit admitting the additional cohort of patients.

Analytical characterization of IgG–cTpp and IgG–Mn-cTpp conjugates

Herein, the conjugation of carboxylated tetraphenylporphyrin or its derivative containing manganese cation and model protein — immunoglobulin G is presented. The obtained IgG–cTpp and IgG–Mn-cTpp conjugates were subsequently used for model immunoassays construction. The IgG–cTpp formation was confirmed using size-exclusion chromatography. Thanks to the unique properties of applied labels the assay analysis was carried out with both spectrophotometric and spectrofluorimetric detection. The assays were performed creating semi-quantitative detection system using 96-well plates. The incubation time, ensuring full saturation of the surface with secondary antibodies was also optimized. Moreover, in the case of IgG–Mn-cTpp conjugates we present the possibility of both direct and indirect determination of the label, the latter based on the catalytic activity of Mn-cTpp, which allows for amplification of the measured signal. We proved that both cTpp and Mn-cTpp may be successfully used for protein labeling and serve as universal tracers for various formats of affinity assays and sensors.

Serial measurement of N-terminal pro-B-type natriuretic peptide and cardiac troponin T for cardiovascular disease risk assessment in the Multi-Ethnic Study of Atherosclerosis (MESA)

BACKGROUND

N-terminal-pro-B-type natriuretic peptide (NT-proBNP) and cardiac troponin T (TnT) predict cardiovascular disease (CVD) risk in a variety of populations. Whether their predictive value varies by ethnicity is unknown. We sought to determine whether NT-proBNP and TnT improve prediction of incident coronary heart disease (CHD) and CVD, independent of CVD risk factors, in a multiethnic population; whether NT-proBNP improves prediction compared with the Framingham Risk Score or the Pooled Cohort Risk Equation; and whether a second NT-proBNP further improves prediction.

METHODS

Both NT-proBNP and TnT were measured in 5,592 MESA white, black, Hispanic, and Chinese participants (60% nonwhite; mean age 62.3 ± 10.3 years) in 2000 to 2002 and 2004 to 2005. We evaluated adjusted risk of incident CHD and CVD based on baseline and change in biomarker concentration.

RESULTS

Participants were followed up through 2011 and incurred 370 CVD events (232 CHD). Concentrations of NT-proBNP and TnT varied by ethnicity. Both NT-proBNP and TnT were associated with an increased risk of events (adjusted hazard ratio [HR] for CHD [95% CI] for fifth quintile vs other 4 quintiles of NT-proBNP, 2.03 [1.50-2.76]; HR for CHD for detectable vs undetectable TnT, 3.95 [2.29-6.81]). N-terminal-pro-B-type natriuretic peptide improved risk prediction and classification compared with the Framingham Risk Score and the Pooled Cohort Risk Equation. Change in NT-proBNP was independently associated with events (HR for CHD per unit increase in ΔlogNT-proBNP, 1.95 [1.16-3.26]). None of the observed associations varied by ethnicity.

CONCLUSIONS

Both NT-proBNP and TnT are predictors of incident CHD, independent of established risk factors and ethnicity, in a multiethnic population without known CVD. Change in NT-proBNP may add additional prognostic information.

Prognostic significance of elevated troponin in non-cardiac hospitalized patients: a systematic review and meta-analysis

Cardiac biomarker troponin can be elevated in patients without a primary cardiac diagnosis and may have prognostic value. We conducted a systematic review to estimate the prevalence and prognostic significance of elevated troponin levels in patients admitted to hospital without a primary cardiac diagnosis. Literature search was done using MEDLINE (1946 to November 2012), EMBASE (1974 to Week 45, 2012), and Cochrane Central Register of Controlled Trials (November 2012). Two independent investigators reviewed full-text studies for final inclusion. We included studies of patients admitted without a primary cardiac diagnosis. Eligible studies compared adverse outcomes in patients with normal versus elevated troponin levels. Twenty-seven studies were included in the meta-analysis. Elevated troponin was associated with increased in-hospital and 30-day mortality (25 studies, 7255 patients, OR 3.88, 95% CI 2.90-5.19, P < 0.0001). Elevated troponin was also associated with increased risk of long-term mortality at 6 months (9 studies, 5368 patients, OR 4.21, 95% CI 1.84-9.64, P < 0.00001). Troponin is an independent predictor of short-term mortality with a pooled adjusted OR of 2.36, 95% CI 1.47-3.76, P < 0.0003. In conclusion, elevated troponin in non-cardiac patients is independently associated with increased mortality.