The Era for High-Sensitivity Cardiac Troponin Has Begun in the US (Finally)

The Translation and Commercialisation of Biomarkers for Cardiovascular Disease—A Review

As a leading cause of mortality and morbidity worldwide, cardiovascular disease and its diagnosis, quantification, and stratification remain significant health issues. Increasingly, patients present with cardiovascular disease in the absence of known risk factors, suggesting the presence of yet unrecognized pathological processes and disease predispositions. Fortunately, a host of emerging cardiovascular biomarkers characterizing and quantifying ischaemic heart disease have shown great promise in both laboratory settings and clinical trials. These have demonstrated improved predictive value additional to widely accepted biomarkers as well as providing insight into molecular phenotypes beneath the broad umbrella of cardiovascular disease that may allow for further personalized treatment regimens. However, the process of translation into clinical practice – particularly navigating the legal and commercial landscape – poses a number of challenges. Practical and legal barriers to the biomarker translational pipeline must be further considered to develop strategies to bring novel biomarkers into the clinical sphere and apply these advances at the patient bedside. Here we review the progress of emerging biomarkers in the cardiovascular space, with particular focus on those relevant to the unmet needs in ischaemic heart disease.

Outcomes Associated with Introduction of the 5th Generation High-Sensitivity Cardiac Troponin in Patients Presenting with Cardiovascular Disorders

BACKGROUND

The new high-sensitivity cardiac troponin T (hs-cTnT) is now widely used in the United States.

OBJECTIVES

We aimed to examine outcomes associated with the introduction of the new 5^th generation hs-cTnT assay among patients presenting to the emergency department (ED) with cardiovascular (CV) disorders.

METHODS

The study comprised 5377 patients presenting to the ED with CV disorders between January and September 2018. Outcomes included rates of direct ED discharge, cardiac testing/procedures, and mortality. CV indications for troponin testing were categorized as rule-out acute coronary syndrome (RO-ACS) and other-CV (O-CV).

RESULTS

Mean age was 62 ± 17 years, and 47% were female. Demographics and medical history did not differ significantly between the troponin groups. The use of hs-cTnT was associated with increased rates of direct discharge from the ED in the RO-ACS (48% vs. 37%; p < 0.01), but not in the O-CV (25% vs. 25%) cohort. Cardiac tests/procedures were more often performed after hs-cTnT vs. cTnT testing in both cohorts (45% vs. 41% for RO-ACS, and 33% vs. 28% for O-CV; p < 0.05 for both). Multivariate analysis demonstrated that hs-cTnT was not associated with a significant increase in postdischarge mortality in both cohorts (RO-ACS: hazard ratio = 1.47 [p = 0.13], O-CV: hazard ratio = 0.97 [p = 0.87]).

CONCLUSIONS

Among patients with RO-ACS, hs-cTnT implementation resulted in increased rates of direct home discharge from the ED, without a significant increase in postdischarge mortality. Among patients presenting with O-CV indication, hs-cTnT implementation resulted in increased rates of cardiac testing procedures without an effect of ED discharge rates or long-term mortality.

Outcomes associated with the high sensitivity cardiac troponin testing in patients presenting with non-cardiovascular disorders

There are limited data regarding the utility of troponin testing in patients presenting with non-cardiovascular (CV) symptoms as the primary manifestation. The study population comprised 2057 patients who presented to the emergency department (ED) of a US healthcare system with non-CV symptoms as the primary manifestation between January and September 2018. We compared the effect of high-sensitivity cardiac troponin T (hs-cTnT) (n = 901) after its introduction vs. 4th generation cTnT (n = 1156) on the following outcomes measures: ED length of stay (LOS), coronary tests/procedures (angiography or stress test), and long-term mortality. Mean age was 64 ± 17 yrs., and 47% were female. Primary non-CV manifestations included pneumonia, obstructive pulmonary disease, infection, abdominal-complaint, and renal failure. Mean follow up was 9 ± 4 months. Patients' demographics and medical history were clinically similar between the two troponin groups. A second cTn test was obtained more frequently in the hs-cTnT than cTnT (84% vs. 32%; p < 0.001), possibly leading to a longer ED stay (8.1 ± 8.2 h vs 5.6 ± 3.4 h, respectively; p < 0.001). Coronary tests/procedures were performed at a significantly higher rate in the hs-cTnT than cTnT following the introduction of the hs-cTnT test (28% vs. 22%, p < 0.001). Multivariate analysis showed that following the introduction of hs-cTnT testing, there was a significant 27% lower risk of long-term mortality from ED admission through follow-up (HR = 0.73, 95%CI 0.54-0.98; p = 0.035). In conclusion, we show that in patients presenting primarily with non-CV disorders, the implementation of the hs-cTnT was associated with a higher rate of diagnostic coronary procedures/interventions, possibly leading to improved long-term survival rates.

Prognostic Utility of a Modified HEART Score When Different Troponin Cut Points Are Used

BACKGROUND

Although the recommended cut point for cardiac troponin (cTn) is the 99th percentile, many institutions use cut points that are multiples higher than the 99th percentile for diagnosing acute myocardial infarction (AMI). Prior studies have shown that patients with a HEART score (HS) ≤ 3 and normal serial cTn values (modified HS) are at low risk for adverse events. This study aimed to evaluate the prognostic utility of the HS when various cTn cut points are used.

METHODS

This was a substudy of High Sensitivity Cardiac Troponin T assay for RAPID Rule-out of Acute Myocardial Infarction (TRAPID-AMI), a multicenter, international trial evaluating a rapid rule-out AMI study using high-sensitivity cardiac troponin T (hs-cTnT). One-thousand two-hundred eighty-two patients were evaluated for AMI from 12 centers in Europe, United States, and Australia from 2011 to 2013. Blood samples of hs-cTnT were collected at presentation and 2 hours, and each patient had a HS calculated. The US Food and Drug Administration approved 99th percentile for hs-cTnT (19 ng/L) was used.

RESULTS

There were 213 (17%) AMIs. Within 30 days, there were an additional 2 AMIs and 8 deaths. The adverse event rates at 30 days (death/AMI) for a HS ≤ 3 and nonelevated hs-cTnT over 2 hours using increasing hs-cTnT cut points ranged from 0.6% to 5.1%.

CONCLUSIONS

Using the recommended 99th percentile cut point for hs-cTnT, the combination of a HS ≤ 3 with nonelevated hs-cTnT values over 2 hours identifies a low-risk cohort who can be considered for discharge from the emergency department without further testing. The prognostic utility of this strategy is greatly lessened as higher hs-cTnT cut points are used.

Cardiovascular Risk Assessment for Noncardiac Surgery: Are We Ready for Biomarkers?

Biomarkers aided perioperative cardiac assessment is a relatively new concept. Cardiac biomarkers with historical significance (aspartate transaminase, dehydrogenase, creatinine kinase and myoglobin) have paved the way for traditional biomarkers (cardiac troponin, C-reactive protein, lipoprotein). Contemporary biomarkers like natriuretic peptides (BNP and ProBNP) are validated risk markers in both acute and chronic cardiac diseases and are showing remarkable promise in predicting serious cardiovascular complications after non-cardiac surgery. This review is intended to provide a critical overview of traditional and contemporary biomarkers for perioperative cardiovascular assessment and management. This review also discusses the potential utility of newer biomarkers like galectin-3, sST-2, GDF-15, TNF-alpha, MiRNAs and many others that can predict inflammation, cardiac remodeling, injury and endogenous stress and need further investigations to establish their clinical utility. Though promising, biomarker led perioperative care is still in infancy and it has not been determined that it can improve clinical outcomes.

Susceptibility of Cardiac Troponin Assays to Biotin Interference

OBJECTIVES

To investigate biotin interference on three cardiac troponin (cTn) assays and demonstrate a method to overcome biotin interference.

METHODS

cTn levels were measured in (1) plasma from healthy volunteers on 10-mg daily biotin supplementation mixed with a plasma with known elevated troponin, (2) plasmas with known elevated cTn after mixing in reagent biotin to simulate supplementation, and (3) biotin-spiked plasma specimens pretreated with streptavidin-agarose beads.

RESULTS

Daily biotin ingestion (10 mg) and studies simulating daily biotin use resulted in significant interference in the Gen5 cardiac troponin T (cTnT) assay; the contemporary Gen 4 cTnT and high-sensitivity cardiac troponin I (hs-cTnI) assays were unaffected. The biotin interference threshold was 31, 315, and more than 2,000 ng/mL for Gen5 cTnT, cTnT, and hs-cTnI assays, respectively. Streptavidin pretreatment blocked biotin interference in cTn assays.

CONCLUSIONS

Biotin interference is possible at plasma concentrations achievable by ingestion of over-the-counter supplements that may lead to delayed or missed diagnosis of myocardial injury with the Gen5 cTnT assay.

Recurrent Hydrochlorothiazide-Induced Acute Respiratory Distress Syndrome Treated With Extracorporeal Membrane Oxygenation

BACKGROUND

Hydrochlorothiazide (HCTZ) is a commonly prescribed sulfonamide thiazide-type diuretic medication that has been associated with rare cases of noncardiogenic pulmonary edema.

CASE REPORT

A man in his 50s with a medical history notable for hypertension was transferred to our institution for evaluation of refractory hypoxemia. After taking an initial dose of HCTZ earlier in the day, he developed progressive respiratory failure and was intubated at a referring hospital. Progressive hypoxemia and acute respiratory distress syndrome (ARDS) developed and he was transferred to our institution for extracorporeal membrane oxygenation (ECMO). Venovenous ECMO (vv-ECMO) was initiated in the Emergency Department and he was admitted to the intensive care unit. After several days of ECMO, his ARDS resolved and he was decannulated and extubated. Further history indicated that he had had two previous episodes of ARDS in the setting of HCTZ use without recognition of the inciting trigger, likely explaining his presentation. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: One of the most commonly prescribed antihypertensives, HCTZ is associated with rare cases of pulmonary edema, which typically develop within minutes to hours of the initial dose of the medication. Although most cases resolve with supportive care, severe cases may require intubation and even vv-ECMO. The mechanism of the reaction is unknown, and affected individuals are typically able to tolerate other sulfonamide medications without issue.

Evaluation of sex-specific cut-off values of high-sensitivity cardiac troponin I and T assays in an emergency department setting - Results from the Linz Troponin (LITROP) study

BACKGROUND

The aim of the present analysis was to evaluate sex-specific cut-off values of a high-sensitivity cardiac troponin T (hs-cTnT) assay and a high-sensitivity cardiac troponin I (hs-cTnI) assay in an emergency department setting.

METHODS

We retrospectively studied 1945 male and 1643 female emergency department patients in whom we had measured both Roche hs-cTnT and Abbott hs-cTnI routinely upon every troponin measurement request. We performed reclassification analyses of sex-specific thresholds versus sex-neutral thresholds of both assays. In addition, we performed sensitivity analyses to find those sex-specific cut-off values for the Roche hs-cTnT and the Abbott hs-cTnI assays with the lowest possible rate of discordant classifications by both assays.

RESULTS

Compared with the classification by the sex-neutral thresholds (i.e., 14 ng/L for hs-cTnT and 26 ng/L for hs-cTnI), using sex-specific thresholds (i.e., 16 ng/L in males and 9 ng/L in females for hs-cTnT; and in 34 ng/L males and 16 ng/L in females for hs-cTnI) resulted in a total reclassification rate of 4% for hs-cTnT and 3% for hs-cTnI in male individuals, and of 11% and 6%, respectively, in female individuals. In our cohort, the sex-specific hs-cTnT cut-off values currently in use (i.e., 16 ng/L in males and 9 ng/L in females) were best matched to a hs-cTnI cut-off value of 11 ng/L in male and 5 ng/L in female individuals. Conversely, the sex-specific hs-cTnI cut-off values currently in use (i.e., 34 ng/L in males and 16 ng/L in females) were best matched to a hs-cTnT cut-off value of 49 ng/L in male and 24 ng/L in female individuals. These "harmonised" cut-off values reduced discordant classifications between both assays by 43-68% compared to using cut-off values currently in use.

CONCLUSION

Especially in women, reclassification rates were high, when using sex specific versus sex-neutral thresholds. Best matching cut-off values for hs-cTnT and hs-cTnI were markedly different to those currently in use. These "harmonised" cut-off values minimised discordant classifications between both assays.

5th generation cardiac troponin I and T assays in clinical routine - A head-to-head comparison with data from the Linz troponin (LITROP) study

BACKGROUND

In Europe, clinicians use so called high-sensitivity assays for the measurement of cardiac troponin I and T (i.e., hs-cTnI and hs-cTnT assays, also termed 5th generation assays) since several years. We aimed at performing a head-to-head comparison of two 5th generation assays in "real life use".

METHODS

We studied 3588 consecutive patients presenting to an emergency department. We used both, a hs-cTnI assay from Abbott and a hs-cTnT assay from Roche in clinical routine. We assessed (1) the capabilities of hs-cTnI and hs-cTnT for the prediction of 3.7 year all-cause mortality; (2) discordant diagnoses of myocardial injury by hs-cTnI and hs-cTnT according to the European gender-neutral 99th percentile upper reference limits (i.e., 26 ng/L and 14 ng/L, respectively); and (3) analyte kinetics in patient with serial troponin measurements.

RESULTS

With respect to prognosis of all-cause mortality, the AUC of hs-cTnI was 0.81 (95% CI, 0.80-0.82), and the AUC of hs-cTnT was 0.85 (95% CI, 0.84-0.86). With respect to discordant diagnoses, 21% of the 3588 patients were classified as having myocardial injury by hs-cTnT but not by hs-cTnI, and < 1% were classified as having myocardial injury by hs-cTnI but not by hs-cTnT. In the patients with serial blood sampling, the median delta values were 6.3 ng/L and 25% for hs-cTnI, and 4.2 ng/L and 16% for hs-cTnT.

CONCLUSION

We found different characteristics of the Abbott hs-cTnI and the Roche hs-cTnT assays, especially when using the European gender-neutral 99th percentile upper reference limits. Clinically, these different characteristics are related to discordant results in the diagnosis and prognosis of patients presenting to an emergency department.