Serial changes in high-sensitivity cardiac troponin I in the early diagnosis of acute myocardial infarction

Machine Learning for Myocardial Infarction Compared With Guideline-Recommended Diagnostic Pathways

BACKGROUND

Collaboration for the Diagnosis and Evaluation of Acute Coronary Syndrome (CoDE-ACS) is a validated clinical decision support tool that uses machine learning with or without serial cardiac troponin measurements at a flexible time point to calculate the probability of myocardial infarction (MI). How CoDE-ACS performs at different time points for serial measurement and compares with guideline-recommended diagnostic pathways that rely on fixed thresholds and time points is uncertain.

METHODS

Patients with possible MI without ST-segment-elevation were enrolled at 12 sites in 5 countries and underwent serial high-sensitivity cardiac troponin I concentration measurement at 0, 1, and 2 hours. Diagnostic performance of the CoDE-ACS model at each time point was determined for index type 1 MI and the effectiveness of previously validated low- and high-probability scores compared with guideline-recommended European Society of Cardiology (ESC) 0/1-hour, ESC 0/2-hour, and High-STEACS (High-Sensitivity Troponin in the Evaluation of Patients With Suspected Acute Coronary Syndrome) pathways.

RESULTS

In total, 4105 patients (mean age, 61 years [interquartile range, 50-74]; 32% women) were included, among whom 575 (14%) had type 1 MI. At presentation, CoDE-ACS identified 56% of patients as low probability, with a negative predictive value and sensitivity of 99.7% (95% CI, 99.5%-99.9%) and 99.0% (98.6%-99.2%), ruling out more patients than the ESC 0-hour and High-STEACS (25% and 35%) pathways. Incorporating a second cardiac troponin measurement, CoDE-ACS identified 65% or 68% of patients as low probability at 1 or 2 hours, for an identical negative predictive value of 99.7% (99.5%-99.9%); 19% or 18% as high probability, with a positive predictive value of 64.9% (63.5%-66.4%) and 68.8% (67.3%-70.1%); and 16% or 14% as intermediate probability. In comparison, after serial measurements, the ESC 0/1-hour, ESC 0/2-hour, and High-STEACS pathways identified 49%, 53%, and 71% of patients as low risk, with a negative predictive value of 100% (99.9%-100%), 100% (99.9%-100%), and 99.7% (99.5%-99.8%); and 20%, 19%, or 29% as high risk, with a positive predictive value of 61.5% (60.0%-63.0%), 65.8% (64.3%-67.2%), and 48.3% (46.8%-49.8%), resulting in 31%, 28%, or 0%, who require further observation in the emergency department, respectively.

CONCLUSIONS

CoDE-ACS performs consistently irrespective of the timing of serial cardiac troponin measurement, identifying more patients as low probability with comparable performance to guideline-recommended pathways for MI. Whether care guided by probabilities can improve the early diagnosis of MI requires prospective evaluation.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT00470587.

External validation of the 0/1h-algorithm and derivation of a 0/2h-algorithm using a new point-of-care Hs-cTnI assay

BACKGROUND

The high-sensitivity cardiac troponin (hs-cTn) I point-of-care (POC) hs-cTnI-PATHFAST assay has recently become clinically available.

METHODS

We aimed to externally validate the hs-cTnI-PATHFAST 0/1h-algorithm recently developed for the early diagnosis of non-ST-segment-elevation myocardial infarction (NSTEMI) and derive and validate a 0/2-algorithm in patients presenting to the emergency department with acute chest discomfort included in a multicenter diagnostic study. Two independent cardiologists centrally adjudicated the final diagnoses using all the clinical and study-specific information available including serial measurements of hs-cTnI-Architect.

RESULTS

Among 1,532 patients (median age 60 years, 33% [n = 501] women), NSTEMI was the final diagnosis in 13%. External validation of the hs-cTnI-PATHFAST 0/1h-algorithm showed very high negative predictive value (NPV; 100% [95%CI, 99.5%-100%]) and sensitivity 100% (95%CI, 98.2%-100%) for rule-out of NSTEMI. Positive predictive value (PPV) and specificity for rule-in of NSTEMI were high (74.9% [95%CI, 68.3%-80.5%] and 96.4% [95%CI, 95.2%-97.3%], respectively). Among 1,207 patients (median age 61 years, 32% [n = 391] women) available for the derivation (n = 848) and validation (n = 359) of the hs-cTnI-PATHFAST 0/2h-algorithm, a 0h-concentration <3 ng/L or a 0h-concentration <4 ng/L with a 2h-delta <4ng/L ruled-out NSTEMI in 52% of patients with a NPV of 100% (95%CI, 98-100) and sensitivity of 100% (95%CI, 92.9%-100%) in the validation cohort. A 0h-concentration ≥90ng/L or a 2h-delta ≥ 55ng/L ruled-in 38 patients (11%): PPV 81.6% (95%CI, 66.6-90.8), specificity 97.7% (95%CI, 95.4-98.9%).

CONCLUSIONS

The POC hs-cTnI-PATHFAST assay allows rapid and effective rule-out and rule-in of NSTEMI using both a 0/1h- and a 0/2h-algorithm with high NPV/sensitivity for rule-out and high PPV/specificity for rule-in.

CLINICAL TRIAL REGISTRATION

NCT00470587.

The utility of delta troponin in diagnosing significant coronary artery disease in patients with symptomatic atrial fibrillation

BACKGROUND

Troponin I (cTnI) elevation is common in patients with atrial fibrillation (AF) but does not reliably indicate underlying coronary ischemia. We investigated whether dynamic changes in cTnI value (delta troponin) are useful in revealing significant coronary artery disease (sCAD) in patients presenting with symptomatic AF.

METHODS

We conducted a retrospective case-control study analyzing serial cTnI values in 231 patients presenting with symptomatic AF who had an objective assessment for underlying CAD within 6 months of the index admission. Diagnostic performance of an elevated cTnI (>0.04 μg/L) only, and elevated cTnI coupled with Youden Index derived cutoffs for absolute and relative changes in troponin, for distinguishing patients with sCAD, was evaluated.

RESULTS

A total of 107 patients had an elevated cTnI on serial measurements. In this group, the area under the receiver operating characteristic curve was 0.69 [95% confidence interval (CI), 0.56-0.81] for relative delta troponin and 0.71 (95% CI, 0.59-0.83) for absolute delta troponin. The optimal diagnostic cutoff for relative delta troponin was > -0.42, and > -0.055 μg/L for absolute delta troponin. The specificity of elevated troponin to diagnose sCAD increased from 56 to 77% when relative delta troponin was added, and to 88% with absolute delta troponin. Although the sensitivity of cTnI elevation (57.1%) decreased to 50% for relative and 35.7% for absolute delta troponin, the negative predictive values were high and similar at 86%.

CONCLUSION

When added to the troponin peak, delta troponin is a promising test for the diagnosis of significant coronary artery disease in patients presenting with symptomatic AF with elevated cTnI. This result requires prospective validation in a larger cohort of patients.

Diagnostic accuracy of a high-sensitivity troponin I assay and external validation of 0/3 h rule out strategies

AIMS

The timely diagnosis and exclusion of acute coronary syndromes in the Emergency Department (ED) remains a challenge. This study aims to evaluate the diagnostic accuracy of a high-sensitivity cardiac troponin I assay (Siemens TNIH) on serial sampling for ED patients as standalone test and in rule-out algorithms as recommendations remain assay specific.

METHODS AND RESULTS

This secondary analysis from a prospective diagnostic accuracy study at 14 centres included ED patients presenting with chest pain of suspected cardiac nature. Serum drawn on arrival and 3 h later was batchtested for TNIH. The target condition was an adjudicated diagnosis of acute myocardial infarction (AMI). We evaluated the diagnostic accuracy of absolute and relative delta criteria and four rule-out strategies. Of 802 included patients, 13.8% had AMI. Absolute delta criteria had superior accuracy to relative criteria (C-statistic 0.94 vs. 0.76, P < 0.001). However, no delta criteria achieved >95.5% sensitivity for AMI when used alone. Ruling out AMI with TNIH below the 99th percentile at 0 and 3 h had 88.3% (95% confidence interval 80.8-93.6%) sensitivity. The adapted European Society of Cardiology (ESC) 0/2 h algorithm had higher sensitivity (98.2%) than both High-STEACS (93.7%, P = 0.03) and the ESC 0/3 h algorithm (79.3%, P < 0.001). These pathways ruled out 63%, 74%, and 88% patients, respectively.

CONCLUSION

With serial sampling over 3 h, the Siemens TNIH assay should be used with a validated algorithm incorporating bespoke cut-offs and absolute delta criteria. In our analysis, the adapted ESC 0/2 h algorithm had greatest sensitivity. 'Ruling out' AMI using the 99th percentile of the assay cannot be recommended.

The absolute and relative changes in high-sensitivity cardiac troponin I are associated with the in-hospital mortality of patients with fulminant myocarditis

Background

We sought to describe the tendency and extent of high-sensitivity cardiac troponin I (hs-cTnI) changes in patients with fulminant myocarditis (FM) after admission and to explore the relationship between the in-hospital mortality of FM and the absolute and relative changes in hs-cTnI within 24 h and 48 h after admission.

Methods

In the retrospective study, the object are patients diagnosed with FM in our single centre. The value of cardiac troponin was recorded after patients admitted to hospital in succession. The absolute and relative changes in hs-cTnI within 24 h and 48 h were described as range distributions. Receiver operating characteristic (ROC) curve and Cox analyses were performed to determine the relationship between in-hospital mortality of FM and hs-cTnI changes.

Results

A total of 83 FM patients admitted to our centre from January 1, 2010 to December 31, 2019 were included; 69 patients survived and 14 patients died. In the survival group, 78% of patients experienced a decline in hs-cTnI within 24 h, while 36% of the mortality group exhibited a declining tendency in hs-cTnI (P = 0.003). Nearly 60% of survival group had a 0–2000 ng/l reduction in troponin from baseline within 24 h of admission. However, troponin levels of 50% of patients in the mortality group were 0–10,000 ng/ L higher than baseline 24 h after admission. Multivariable logistic analysis revealed that the declining tendency of hs-cTnI within 24 h, in addition to time from onset to admittance to hospital, intravenous immunoglobulin treatment and the abnormal level of creatinine, were associated with the in-hospital mortality of FM (for the declining tendency of hs-cTnI within 24 h, OR = 0.10, 95% CI 0.02–0.68, P = 0.018). The ROC curve revealed optimal cut-off values of − 618 ng/l for absolute change within 24 h (AUC = 0.800, P < 0.01), − 4389 ng/l for absolute change within 48 h (area under the curve = 0.711, P < 0.01), − 28.46% for relative change within 24 h (AUC = 0.810, P < 0.01), and − 52.23% for relative change within 48 h (AUC = 0.795, P < 0.01). Absolute changes and relative changes in hs-cTnI within 24 h and 48 h were strong predictors of in-hospital mortality by Cox regression analysis after adjustment for sex, time from onset to admission, and occurrence of ventricular tachycardia or ventricular fibrillation.

Conclusion

Most FM patients who survived experienced a decline in hs-cTnI within 24 h. The absolute and relative changes in hs-cTnI within 24 h and 48 h were strong predictors of in-hospital mortality.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-021-02386-8.

Novel Criteria for the Observe-Zone of the ESC 0/1h-hs-cTnT Algorithm

Background: The non-ST elevation myocardial infarction (NSTEMI) guidelines of the European Society of Cardiology (ESC) recommend a 3h cardiac troponin determination in patients triaged to the observe-zone of the ESC 0/1h-algorithm; however, no specific cut-off for further triage is endorsed. Recently, a specific cut-off for 0/3h high-sensitivity cardiac troponin T (hs-cTnT) change (7ng/L) was proposed warranting external validation. Methods: Patients presenting with acute chest discomfort to the emergency department were prospectively enrolled into an international multicenter diagnostic study. Final diagnoses were centrally adjudicated by two independent cardiologists applying the 4th universal definition of MI, based on complete cardiac work-up, cardiac imaging and serial hs-cTnT. Hs-cTnT concentrations were measured at presentation, after 1h and 3h. The objective was to externally validate the proposed cut-off, and if necessary, derive and internally as well as externally validate novel 0/3h-criteria for the observe-zone of the ESC 0/1h-hs-cTnT-algorithm in an independent multicenter cohort. Results: Among 2076 eligible patients, application of the ESC 0/1h-hs-cTnT-algorithm triaged 1512 patients (72.8%) to either rule-out or rule-in of NSTEMI, remaining 564 patients (27.2%) in the observe-zone (adjudicated NSTEMI prevalence 120/564 patients, 21.3%). The suggested 0/3h-hs-cTnT-change of <7ng/L triaged 517 patients (91.7%) towards rule-out, resulting in a sensitivity of 33.3% (95%CI 25.5-42.2), missing 80 patients with NSTEMI, and ≥7ng/L triaged 47 patients towards rule-in (8.3%), resulting in a specificity of 98.4% (95%CI 96.8-99.2). Novel derived 0/3h-criteria for the observe-zone patients ruled-out NSTEMI with a 3h hs-cTnT concentration <15 ng/L and a 0/3h-hs-cTnT absolute change <4 ng/L, triaging 138 patients (25%) towards rule-out, resulting in a sensitivity of 99.2% (95%CI 96.0-99.9), missing 1 patient with NSTEMI. A 0/3h-hs-cTnT absolute change ≥6 ng/L triaged 63 patients (11.2%) towards rule-in, resulting in a specificity of 98% (95%CI 96.2-98.9) Thereby, the novel 0/3h-criteria reduced the number of patients in the observe zone by 36%, and the number of T1MI by 50%. Findings were confirmed in both internal and external validation. Conclusions: A combination of a 3h hs-cTnT concentration (<15 ng/L) and a 0/3h absolute change (<4 ng/L) is necessary to safely rule-out NSTEMI in patients remaining in the observe-zone of the ESC 0/1h-hs-cTnT-algorithm. Clinical Trial Registration: URL: https://clinicaltrials.gov Unique Identifier: NCT00470587.

Establishment and Application of a Dual-Labeling Time-Resolved Fluorescence Immunoassay Method for Simultaneous Detection of the Troponin I-C Complex and Full-Size-Troponin I

Background: The measurement of cardiac troponin I (cTnI) is widely used in the diagnosis of acute myocardial infarction (AMI). Although existing cTnI detection methods measure total cTnI, the significance of undegraded full-size-cTnI levels is still not well-understood. In this study, we have established a novel dual-labeling time-resolved fluorescence immunoassay (TRFIA) technique that simultaneously detects the cTnI-C complex and full-size-cTnI, allowing us to explore the clinical value of full-size-cTnI determination.

Methods: An antibody against the 23–43 amino acid region of cTnI protected by endogenous cTnC is coupled to magnetic beads to provide a solid-phase antibody for capturing all cTnI. An antibody against cTnC in the cTnI-C complex labeled with Eu³⁺ was used to detect the cTnI-C complex, and an antibody labeled with Sm³⁺ near the C-terminal 190–203 amino acids of cTnI was used to detect full-size-cTnI. Through dual-labeling TRFIA, cTnI-C complex, full-size-cTnI, and the full-size-cTnI/cTnI-C ratio can be detected simultaneously. The dual-labeling TRFIA technique was used to analyze serum samples collected at different times during treatment and compare their full-size-cTnI/cTnI-C ratios.

Results: The sensitivity for the cTnI-C-TRFIA complex was 0.02 ng/mL, the measurement range was 0.02–40 ng/mL, the average intra-batch coefficient of variation (CV) was 4.35%, and the inter-average CV was 6.23%. The correlation coefficient between cTnI-C-TRFIA and commercial cTnI-CLIA methods was R² = 0.8887. The sensitivity for full-size-cTnI-TRFIA was 0.04 ng/mL, the measurement range was 0.04–40 ng/mL, the average intra-batch CV was 4.95%, and the average inter-batch CV was 7.79%. The correlation coefficient between full-size-cTnI-TRFIA and commercial cTnI-CLIA methods was R² = 0.7247.

Conclusions: Dual-labeling full-size-cTnI/cTnI-C-TRFIA analysis is helpful for determining the length of time of chest pain before admission and the degree of continuous release of cTnI in the myocardium. Thus, it is more for early prognosis than just detecting cTnI.

Predicting Acute Myocardial Infarction with a Single Blood Draw

BACKGROUND

We desired to determine cardiac troponin (cTn) concentrations necessary to achieve a positive predictive value (PPV) of ≥75% for acute myocardial infarction (AMI) to justify immediate admission of patients to a monitored unit and, in general, early coronary angiography.

METHODS

In a prospective multicenter diagnostic study enrolling patients presenting to the emergency department with symptoms suggestive of AMI, final diagnoses were adjudicated by 2 independent cardiologists based on clinical information including cardiac imaging. cTn concentrations were measured using 5 different sensitive and high-sensitivity cTn (hs-cTn) assays in a blinded fashion at presentation and serially thereafter. The diagnostic end point was PPV for rule-in of AMI of initial cTn concentrations alone and in combination with early changes.

RESULTS

Among 3828 patients, 616 (16%) had an AMI. At presentation, 7% to 14% of patients had cTnT/I concentrations associated with a PPV of ≥75%. Adding absolute or relative changes did not significantly further increase the PPV. PPVs increased from 46.5% (95% CI, 43.6–49.4) for hs-cTnT at presentation &gt;14 ng/L to 78.9% (95% CI, 74.7–82.5) for &gt;52 ng/L (P &lt; 0.001), whereas PPVs in higher hs-cTnT strata remained largely unchanged [e.g., 82.4% (95% CI, 77.5–86.7) for &gt;80 ng/L vs 83.9% (95% CI, 76.0–90.1) for &gt;200 ng/L (P = 0.72)]. The addition of early changes in hs-cTnT further increased the PPV up to 60 ng/L, but not for higher concentrations.

CONCLUSIONS

Serial sampling does not seem necessary for predicting AMI and concurrent decision-making in about 10% of patients, as it only marginally increases the PPV for AMI and not in a statistically or clinically significant way.

ClinicalTrials.gov Identifier

NCT00470587.

Contemporary Emergency Department Management of Patients with Chest Pain: A Concise Review and Guide for the High-Sensitivity Troponin Era

This article synthesizes current best evidence for the evaluation of patients with suspected acute coronary syndrome (ACS) using high-sensitivity troponin assays, enabling physicians to effectively incorporate them into practice. Unlike conventional assays, high-sensitivity assays can precisely measure blood cardiac troponin concentrations in the vast majority of healthy individuals, facilitating the creation of rapid diagnostic algorithms. Very low troponin concentrations on presentation accurately rule out acute myocardial infarction (AMI) and enable the discharge of approximately 20% of patients after a single test, whereas an additional 30%-40% of patients can be safely discharged after short-interval serial sampling in as little as 1 or 2 hours. In contrast, highly abnormal troponin concentrations on presentation (more than 5 times the upper reference limit) or rapidly rising levels on serial testing can rapidly rule in AMI with high specificity. However, approximately one-third of patients remain in a biomarker-indeterminate "observation zone" even after serial sampling. These patients pose a disposition challenge to clinicians because although the differential diagnosis of elevated troponin concentrations is broad, these patients have an increased risk for short-term major adverse cardiac events. Use of repeated serial troponin sampling and structured clinical prediction tools may assist disposition for these patients, because no validated pathways currently exist to guide clinicians. Ongoing research to tailor diagnostic thresholds to individual patient characteristics may enable improved diagnostic accuracy and usher in a new era of personalized medicine in the evaluation of suspected ACS.

Differentiation of cardiomyocytes from amniotic fluid‑derived mesenchymal stem cells by combined induction with transforming growth factor β1 and 5‑azacytidine

As a novel type of seed cell, amniotic fluid-derived mesenchymal stem cells (AFMSCs) are promising for the regeneration of myocardial cells. A focus of cardiovascular regenerative medicine is to improve the efficiency of AFMSC differentiation. The present study replaced the traditional method of AFMSC differentiation with a combined induction method, in order to improve the efficiency of directional differentiation. AFMSCs were obtained from rabbit amniotic fluid samples, and western blot analysis was performed to analyze the expression of octamer-binding transcription factor 4 (OCT4), and tumorigenicity experiments were conducted. AFMSCs were divided into the following 4 groups: Induction with transforming growth factor β1 (TGFβ1); induction with 5-azacytidine (5Aza); induction with TGFβ1 and 5Aza combined; and untreated controls. Reverse transcription-quantitative polymerase chain reaction was performed to analyze the expression of cardiac-specific GATA binding protein 4 (GATA4), and immunofluorescence was employed to analyze the expression of cardiac troponin T (cTnT). In addition, western blotting was performed to analyze the expression of connexin 43, and transmission electron microscopy was used to observe the ultrastructure of the differentiated cells. AFMSCs exhibited positive OCT4 expression and were not observed to induce tumor development in nude mice. The expression levels of GATA4, cTnT, and connexin 43 in the combined induction group were markedly higher when compared with the remaining groups. Transmission electron microscopy analysis revealed that differentiated cells exhibited myocardial cell characteristics. In conclusion, AFMSCs are multipotent, non-tumorigenic cells that are capable of differentiating into cardiomyocyte-like cells. This combined induction method may improve the efficiency of directed differentiation.

Safety and efficacy of the 0 h/3 h protocol for rapid rule out of myocardial infarction

BACKGROUND

The early and accurate diagnosis of acute myocardial infarction (AMI) is an important medical and economic challenge. We aimed to prospectively evaluate the performance of the new European Society of Cardiology rapid 0-hour/3-hour (0 h/3 h) rule out protocol for AMI.

METHODS

We enrolled 2,727 consecutive patients presenting with suspected AMI without persistent ST-segment elevation to the emergency department in a prospective international multicenter study. The final diagnosis was adjudicated by 2 independent cardiologists. The performance of the 0 h/3 h rule out protocol was evaluated using 4 high-sensitivity (primary analysis) and 3 sensitive cardiac troponin (cTn) assays.

RESULTS

Acute myocardial infarction was the final diagnosis in 473 patients (17.3%). Using the 4 high-sensitivity cTn assays, the 0-hour rule out protocol correctly ruled out 99.8% (95% [confidence interval] CI, 98.7%-100%), 99.6% (95% CI, 98.5%-99.9%), 100% (95% CI, 97.9%-100%), and 100% (95% CI, 98.0%-100%) of late presenters (>6 h from chest pain onset). The 3-hour rule out protocol correctly ruled out 99.9% (95% CI, 99.1%-100%), 99.5% (95% CI, 98.3%-99.9%), 100% (95% CI, 98.1%-100%), and 100% (95% CI, 98.2%-100%) of early presenters (<6 h from chest pain onset). Using the 3 sensitive cTn assays, the 0-hour rule out protocol correctly ruled out 99.6% (95% CI, 98.6%-99.9%), 99.0% (95% CI, 96.9%-99.7%), and 99.1% (95% CI, 97.2%-99.8%) of late presenters; and the 3-hour rule out protocol correctly ruled out 99.4% (95% CI, 98.3%-99.8%), 99.2% (95% CI, 97.3%-99.8%), and 99.0% (95% CI, 97.2%-99.7%) of early presenters. Overall, the 0 h/3 h rule out protocol assigned 40% to 60% of patients to rule out. None of the patients assigned rule out died during 3-months follow-up.

CONCLUSIONS

The 0 h/3 h rule out protocol seems to allow the accurate rule out of AMI using both high-sensitivity and sensitive cTn measurements in conjunction with clinical assessment. Additional studies are warranted for external validation.

One-hour rule-in and rule-out of acute myocardial infarction using high-sensitivity cardiac troponin I

We aimed to prospectively derive and validate a novel 0-/1-hour algorithm using high-sensitivity cardiac troponin I (hs-cTnI) for the early "rule-out" and "rule-in" of acute myocardial infarction (AMI).

METHODS

In a prospective multicenter diagnostic study, we enrolled 1,500 patients presenting with suspected AMI to the emergency department. The final diagnosis was centrally adjudicated by 2 independent cardiologists blinded to hs-cTnI concentrations. The hs-cTnI (Siemens Vista) 0-/1-hour algorithm incorporated measurements performed at baseline and absolute changes within 1 hour, was derived in the first 750 patients (derivation cohort), and then validated in the second 750 (validation cohort).

RESULTS

Overall, AMI was the final diagnosis in 16% of patients. Applying the hs-cTnI 0-/1-hour algorithm developed in the derivation cohort to the validation cohort, 57% of patients could be classified as "rule-out"; 10%, as "rule-in"; and 33%, as "observe." In the validation cohort, the sensitivity and the negative predictive value for AMI in the "rule-out" zone were 100% (95% CI 96%-100%) and 100% (95% CI 99%-100%), respectively. The specificity and the positive predictive value (PPV) for AMI in the "rule-in" zone were 96% (95% CI 94%-97%) and 70% (95% CI 60%-79%), respectively. Negative predictive value and positive predictive value of the 0-/1-hour algorithm were higher compared to the standard of care combining hs-cTnI with the electrocardiogram (both P < .001).

CONCLUSION

The hs-cTnI 0-/1-hour algorithm performs very well for early rule-out as well as rule-in of AMI. The clinical implications are that used in conjunction with all other clinical information, the 0-/1-hour algorithm will be a safe and effective approach to substantially reduce time to diagnosis.

hs-Troponin I Followed by CT Angiography Improves Acute Coronary Syndrome Risk Stratification Accuracy and Work-Up in Acute Chest Pain Patients: Results From ROMICAT II Trial

OBJECTIVES

This study compared diagnostic accuracy of conventional troponin/traditional coronary artery disease (CAD) assessment and highly sensitive troponin (hsTn) I/advanced CAD assessment for acute coronary syndrome (ACS) during the index hospitalization.

BACKGROUND

hsTnI and advanced assessment of CAD using coronary computed tomography angiography (CTA) are promising candidates to improve the accuracy of emergency department evaluation of patients with suspected ACS.

METHODS

We performed an observational cohort study in patients with suspected ACS enrolled in the ROMICAT II (Rule Out Myocardial Infarction/Ischemia using Computer Assisted Tomography) trial and randomized to coronary CTA who also had hsTnI measurement at the time of the emergency department presentation. We assessed coronary CTA for traditional (no CAD, nonobstructive CAD, ≥50% stenosis) and advanced features of CAD (≥50% stenosis, high-risk plaque features: positive remodeling, low <30-Hounsfield units plaque, napkin-ring sign, spotty calcium).

RESULTS

Of 160 patients (mean age: 53 ± 8 years, 40% women) 10.6% were diagnosed with ACS. The ACS rate in patients with hsTnI below the limit of detection (n = 9, 5.6%), intermediate (n = 139, 86.9%), and above the 99th percentile (n = 12, 7.5%) was 0%, 8.6%, and 58.3%, respectively. Absence of ≥50% stenosis and high-risk plaque ruled out ACS in patients with intermediate hsTnI (n = 87, 54.4%; ACS rate 0%), whereas patients with both ≥50% stenosis and high-risk plaque were at high risk (n = 13, 8.1%; ACS rate 69.2%) and patients with either ≥50% stenosis or high-risk plaque were at intermediate risk for ACS (n = 39, 24.4%; ACS rate 7.7%). hsTnI/advanced coronary CTA assessment significantly improved the diagnostic accuracy for ACS as compared to conventional troponin/traditional coronary CTA (area under the curve 0.84, 95% confidence interval [CI]: 0.80 to .88 vs. 0.74, 95% CI: 0.70 to 0.78; p < 0.001).

CONCLUSIONS

hsTnI at the time of presentation followed by early advanced coronary CTA assessment improves the risk stratification and diagnostic accuracy for ACS as compared to conventional troponin and traditional coronary CTA assessment. (Multicenter Study to Rule Out Myocardial Infarction/Ischemia by Cardiac Computed Tomography [ROMICAT-II]; NCT01084239).

High-sensitivity cardiac troponin assays: answers to frequently asked questions

Cardiac troponin (cTn) assays have quickly gained in analytical sensitivity to become what are termed 'high-sensitivity cardiac troponin' (hs-cTn) assays, bringing a flurry of dense yet incomplete literature data. The net result is that cTn assays are not yet standardized and there are still no consensus-built data on how to use and interpret cTn assay results. To address these issues, the authors take cues and clues from multiple disciplines to bring responses to frequently asked questions. In brief, the effective use of hs-cTn hinges on knowing: specific assay characteristics, particularly precision at the 99th percentile of a reference population; factors of variation at the 99th percentile value; and the high-individuality of hs-cTn assays, for which the notion of individual kinetics is more informative than straight reference to 'normal' values. The significance of patterns of change between two assay measurements has not yet been documented for every hs-cTn assay. Clinicians need to work hand-in-hand with medical biologists to better understand how to use hs-cTn assays in routine practice.

High-sensitivity troponin: where are we now and where do we go from here?

High-sensitivity troponin (hsTn) assays are used clinically in most parts of the world and are expected to be approved by the US FDA for clinical use in the USA soon. Clinical use of hsTn leads to improvements in the detection of myocardial injury, shorter time to ruling out acute myocardial infarction, improved risk-stratification of patients with heart failure and atrial fibrillation among others. HsTn may also guide strategies for primary and secondary prevention of cardiovascular disease. However, unmet challenges remain, including distinguishing between acute and chronic hsTn elevations, distinguishing between type 1 and type 2 acute myocardial infarction and determining whether to use gender-neutral or gender-specific reference values.

Weekly and 90-minute biological variations in cardiac troponin T and cardiac troponin I in hemodialysis patients and healthy controls

BACKGROUND

Myocardial infarction (MI) is diagnosed by the finding of a single cardiac troponin value above the 99th percentile and a significant time-dependent change in cardiac troponin concentration. The aim of this study was to determine the 90-min and weekly biological variations, the reference change value (RCV), and the index of individuality (II) of high-sensitivity cardiac troponin T (hs-cTnT) (Roche Diagnostics) and hs-cTnI (Abbott Diagnostics) in patients receiving hemodialysis (HD) and in healthy individuals.

METHOD

Blood samples were collected from 19 HD patients (on an HD-free day) and 20 healthy individuals at 90-min intervals over a 6-h period (between 08:30 and 14:30) and before the midweek HD treatment for 10 weeks. The within-person variation (CVi), between-person variation, RCV, and II were calculated.

RESULTS

During the 6-h sampling period, the concentrations of hs-cTnT (both groups) and hs-cTnI (HD patients only) decreased on average by 0.8% to 1.7% per hour, respectively. These declining trends were included in the calculation of a 90-min asymmetric RCV: -8%/+5% in HD patients (hs-cTnT), -18%/+21% in HD patients (hs-cTnI), -27%/+29% in healthy individuals (hs-cTnT), and -39%/+64% in healthy individuals (hs-cTnI). The II was low in both groups for both assays. The weekly CVi values were approximately 8% (hs-cTnT) and 15% (hs-cTnI) in both groups.

CONCLUSIONS

When using a cardiac troponin change of 20%-50% to diagnose an MI, the false-positive rate is likely to be lower for the hs-cTnT assay than for the hs-cTnI assay. The low II suggests that use of a diagnostic cutoff value can be omitted.