Defining a reference population to determine the 99th percentile of a contemporary sensitive cardiac troponin I assay

Frequency histograms of three high-sensitivity cardiac troponin assays in a reference population

Background

Cardiac troponin (cTn) values above the 99th percentile upper reference limit (URL) indicate myocardial injury. We established 99th percentile URLs for three high‐sensitivity cTn (hs‐cTn) assays (Beckman Coulter Access hs‐cTnI, Abbott STAT hs‐cTnI, and Roche Elecsys hs‐cTnT) using a healthy population in Korea.

Methods

Each cTn value was measured by three assays and analyzed by dividing by gender and age.

Results

The frequency histograms of log‐transformed cTn values for Beckman and Abbott assays exhibited a bell‐shaped distribution. The 99th percentile URLs were 9.8, 17.4, and 17.3 ng/L in the total population; 10.9/9.0, 18.9/17.0, and 18.9/17.7 ng/L in the male/female population (p < 0.001 for all three assays); and 11.2/7.2, 19.9/14.5, and 22.7/9.3 ng/L in the older/younger population (p < 0.001 for all three assays) for Beckman, Abbott, and Roche assays, respectively.

Conclusion

Among the three assays, bell‐shaped distributions were observed in a frequency histogram of log‐transformed cTn values for healthy population in Beckman and Abbott assays. Also, our findings show that the 99th percentile URLs for cTn levels vary not only by gender but age.

NT-ProBNP and high-sensitivity troponin T as screening tests for subclinical chronic heart failure in a general population

Aims

The aim of this study was to establish age‐specific and sex‐specific cut‐off values for N‐terminal pro‐brain natriuretic peptide (NT‐proBNP) and high‐sensitivity troponin T (hs‐troponin T) in healthy subjects and assess cardiac biomarkers as screening tools for subclinical heart failure (HF) in a general population.

Methods and results

Altogether, 1936 participants were randomly selected from the general population Tromsø 7 study in Northern Norway. Diagnostic accuracy (sensitivity, specificity, and negative and positive predictive value) of cardiac markers for echocardiographically defined subclinical HF was evaluated. The receiver‐operating characteristic analysis showed that areas under the curve were relatively low (under 0.75) for both NT‐proBNP and hs‐troponin T, suggesting that the diagnostic accuracy of these biomarkers for subclinical HF was not excellent, especially for mild forms of HF and younger age group 40–49 years. Sex‐specific and age‐specific cut‐offs for hs‐troponin T (99th percentiles) and NT‐proBNP (97.5th percentiles) were established in healthy subjects from the same general population. The sex‐specific and age‐specific cut‐offs for NT‐proBNP had higher specificity for subclinical HF compared with the previously established single cut‐off 125 pg/mL. Age‐specific cut‐off for hs‐troponin T (18 ng/L) for men ≥60 years had also higher specificity than the single cut‐off 14 ng/L. These cut‐offs had high specificity, but low sensitivity, that makes hs‐troponin T and NT‐proBNP good biomarkers to rule in HF in case of a positive test, but not good enough to rule out all unrecognized HF due to false negative results.

Conclusions

N‐terminal pro‐brain natriuretic peptide and hs‐troponin T are suboptimal screening tools for subclinical HF in a general population due to low sensitivity.

Ultra-highly sensitive cardiac troponin I: Age and sex differences in healthy individuals

Background

Associations between elevated circulating cardiac troponin I (cTnI) levels and adverse cardiac outcomes were established prior to the ability to measure extremely low levels of cTnI. Immunoassays that achieve precise ultra-highly sensitive quantification of cTnI (u-hs-cTnI) will allow accurate measurement in healthy subjects. We aimed to evaluate the distribution of u-hs-cTnI values measured by (Simoa HD-1 Analyzer, Quanterix Corporation, Lexington, MA) in healthy subjects and characterize relations to sex and age.

Methods

Two independent, healthy cohorts (total of 200 women, 200 men) aged 18-86 years were analyzed in duplicate using the u-hs-cTnI Immunoassay. The u-hs-cTnI 99th percentiles were calculated as the upper limits considering a robust estimation against outliers with 90% confidence intervals. The Quanterix immunoassay analytical performance was established and compared to an existing clinical assay (ARCHITECT STAT High Sensitivity Troponin I, Abbott Laboratories, Wiesbaden, Germany).

Results

The lower limit of detection of the u-hs-cTnI assay was calculated to be 0.005 ng/L; we accurately quantified u-hs-cTnI in 95% of healthy individuals. The Quanterix immunoassay within overlapping concentrations correlated with the Abbott assay (R2 = 0.932). The calculated combined 99th percentile was 7.94 ng/L (90% Confidence Interval [CI], 5.47-10.52). Women had lower mean u-hs-cTnI concentrations than men under the age of 40 years. The sex-specific 99th percentile for female vs. male individuals was 4.89 ng/L (90%CI, 3.71-6.25) and 10.49 ng/L (90%CI, 5.19-15.06), respectively.

Conclusion

The Quanterix immunoassay provides precise quantification in 95% of healthy individuals. Women under the age of 40 years have significantly lower levels of u-hs-cTnI than men.

Diagnosis and prognosis of myocardial infarction on a plasmonic chip

Cardiovascular diseases lead to 31.5% of deaths globally, and particularly myocardial infarction (MI) results in 7.4 million deaths per year. Diagnosis of MI and monitoring for prognostic use are critical for clinical management and biomedical research, which require advanced tools with accuracy and speed. Herein, we developed a plasmonic gold nano-island (pGold) chip assay for diagnosis and monitoring of MI. On-chip microarray analysis of serum biomarkers (e.g., cardiac troponin I) afforded up to 130-fold enhancement of near-infrared fluorescence for ultra-sensitive and quantitative detection within controlled periods, using 10 μL of serum only. The pGold chip assay achieved MI diagnostic sensitivity of 100% and specificity of 95.54%, superior to the standard chemiluminescence immunoassay in cardiovascular clinics. Further, we monitored biomarker concentrations regarding percutaneous coronary intervention for prognostic purpose. Our work demonstrated a designed approach using plasmonic materials for enhanced diagnosis and monitoring for prognostic use towards point-of-care testing.

Identification of acute myocardial infarction in elderly patients using optimized highly sensitive troponin I thresholds

Purpose: Established diagnostic thresholds for high-sensitivity cardiac troponins (hs-cTn) might not apply for elderly patients as they are elevated irrespective of the presence of an acute myocardial infarction (AMI). Aim of the present study was to investigate hs-cTnI in elderly patients with suspected AMI and to calculate optimized diagnostic cutoffs. Material and methods: Data from a prospective multi-centre study and from a second independent prospective single-centre cohort study were analysed. A number of 2903 patients were eligible for further analysis. Patients > 70 years were classified as elderly. hs-cTnI was measured upon admission. Results: Around 34.7% of 2903 patients were classified as elderly. Around 22.5% of elderly patients were finally diagnosed with AMI. Elderly patients had higher hs-cTnI levels at admission irrespective of the final diagnosis (p < 0.001). According to the AUROC, hs-cTnI was a strong marker for detection of AMI in elderly patients. Application of the 99th percentile cutoffs showed a substantially lower specificity in elderly. By using optimized thresholds, specificity was improved to levels as in younger patients in both cohorts but accompanied with a decrease in sensitivity. Conclusions: hs-cTnI levels have a lower specificity for detecting AMI in elderly patients. This lower specificity can be improved by using hs-cTnI thresholds optimized for elderly patients.

Collection of human biological samples for research purpose: Key challenges and patients’ perspectives

The development and the access to collections of human biological samples is one of the major challenges for health research. In recent years, biological resource centres (BRCs) have developed in such a way that they provide all activities relating to the handling of samples. In this context, France is undoubtedly a pioneering country, because most of the biological collections available were created on the basis of themed research projects, which involved a particular donor phenotype. The round table was an opportunity to emphasise the persistence of some pitfalls particularly in relation to ensuring the consistency of different regulatory pathways. It also gave the opportunity to question and make recommendations on aspects of governance of biological collections and the BRCs, to state the challenges linked to scientific and economic valorisation and to consider the place of patients and the general public. The development of specific education in public health and research is essential to underline that these initiatives are necessary for developing new diagnostic and therapeutic procedures.

Identification of Periprocedural Myocardial Infarction Using a High-Sensitivity Troponin I Assay in Patients Who Underwent Transcatheter Aortic Valve Implantation

Periprocedural myocardial infarction (MI), a rare complication after transcatheter aortic valve implantation (TAVI), is associated with worse outcome. According to the Valve Academic Research Consortium (VARC-2), MI is defined by an increase in cardiac troponin (cTn) and creatine kinase MB (CK-MB) levels; however, many patients show periprocedurally elevated cTn without clinical evidence of MI. The aims of this study were to establish reference values of cardiac troponin I measured with a high-sensitivity assay (hs-cTnI) and to assess the periprocedural diagnostic value of this biomarker in patients who underwent TAVI. Hs-cTnI and CK-MB levels were assessed before and up to 3 days after transfemoral (TF) or transapical (TA) TAVI in 515 patients. A high proportion (61.2%) of patients had elevated hs-cTnI at baseline. According to VARC-2 criteria, almost all TA-patients (99.5%) showed an MI based on hs-cTnI compared with 4.2% based on CK-MB. In TF-patients, 81.1% had an MI based on hs-cTnI compared with 9.0% based on CK-MB. Only 10 patients (2%), however, had a type 1 MI. The ninety-ninth percentile for hs-cTnI was 285 ng/L in the TAVI cohort. After applying a TAVI-specific cutoff the frequency of MI was lower and more realistic (TF: 5% vs 81.1%; p <0.001; TA: 22.2% vs 99.5%; p <0.001). In conclusion, the VARC-2 definition leads to an overestimation of periprocedural MI. Our new TAVI-specific reference values yield a more realistic estimation of the myocardial ischemic risk. hs-cTnI, however, does not seem to be the biomarker of choice for MI detection in this setting.

Prognostic Significance of Troponin Elevation for Long-Term Mortality after Ischemic Stroke

Background and Purpose

Troponin, a marker of myocardial injury, frequently increases and is related with poor outcome in ischemic stroke patients. However, the long-term outcome of this elevation remains uncertain. We, therefore, investigated the prognostic significance of troponin elevation for long-term mortality, and explored factors affecting troponin elevation after ischemic stroke.

Methods

We retrospectively analyzed the medical data of stroke patients who were admitted within 24 hours of symptom onset and underwent a serum cardiac troponin I test at admission during a five-year period. Information on mortality as the outcome was obtained from the National Death Certificate system.

Results

A total of 1,692 patients were eligible for inclusion with 33 months of median follow-up. Troponin elevation that exceeded the 99th percentile (>0.04 ng/mL) of values was detected in 166 patients (9.8%). After adjusting for baseline characteristics, troponin elevation was associated with previous ischemic heart disease and congestive heart failure, comorbid atrial fibrillation and active cancer, and increased National Institutes of Health Stroke Scale score. Patients with troponin elevation had a high risk of overall death (hazard ratio [HR] 1.83, 95% confidence interval [CI] 1.40–2.40), including stroke-related (HR 1.71, 95% CI 1.14–2.55), cardiac-related (HR 3.17, 95% CI 1.49–6.74), and cancer-related (HR 1.98, 95% CI 1.14–3.45) death than those without troponin elevation.

Conclusions

Troponin elevation in the acute stage of ischemic stroke was associated with long-term mortality, mainly due to increased stroke- and cancer-related death in the first year and cardiacrelated death in the later period.

GDF-15 predicts cardiovascular events in acute chest pain patients

Background

Treatment of patients presenting with possible acute myocardial infarction (AMI) is based on timely diagnosis and proper risk stratification aided by biomarkers. We aimed at evaluating the predictive value of GDF-15 in patients presenting with symptoms suggestive of AMI.

Methods

Consecutive patients presenting with suspected AMI were enrolled in three study centers. Cardiovascular events were assessed during a follow-up period of 6 months with a combined endpoint of death or MI.

Results

From the 1818 enrolled patients (m/f = 1208/610), 413 (22.7%) had an acute MI and 63 patients reached the combined endpoint. Patients with MI and patients with adverse outcome had higher GDF-15 levels compared with non-MI patients (967.1pg/mL vs. 692.2 pg/L, p<0.001) and with event-free patients (1660 pg/mL vs. 756.6 pg/L, p<0.001). GDF-15 levels were lower in patients with SYNTAX score ≤ 22 (797.3 pg/mL vs. 947.2 pg/L, p = 0.036). Increased GDF-15 levels on admission were associated with a hazard ratio of 2.1 for death or MI (95%CI: 1.67–2.65, p<0.001) in a model adjusted for age and sex and of 1.57 (1.13–2.19, p = 0.008) adjusted for the GRACE score variables. GDF-15 showed a relevant reclassification with regards to the GRACE score with an overall net reclassification index (NRI) of 12.5% and an integrated discrimination improvement (IDI) of 14.56% (p = 0.006).

Conclusion

GDF-15 is an independent predictor of future cardiovascular events in patients presenting with suspected MI. GDF-15 levels correlate with the severity of CAD and can identify and risk-stratify patients who need coronary revascularization.

The 99th percentile of reference population for cTnI and cTnT assay: methodology, pathophysiology and clinical implications

According to recent international guidelines, including the 2012 Third Universal Definiton of Myocardial Infarction by the Joint ESC/ACCF/AHA/WHF Task Force, an increase in cardiac troponin (cTn) levels over the 99th percentile upper reference limit (99th URL) should be considered clinically relevant, this cut-off being measured with an imprecision ≤10 CV%. In theory 99th URL values strongly depend not only on demographic and physiological variables (i.e. criteria for considering the reference population “healthy”), but also on the analytical performance of cTn methods and mathematical algorithms used for the calculation. The aim of the present article was therefore to review the methodological and pathophysiological factors affecting the evaluation and calculation of the 99th URL for cTn assay. The critical analysis made showed that no uniform procedure is followed, and nor have experts or regulatory bodies provided uniform guidelines for researchers or cTn assays manufacturers as an aid in “their quest to define normality”. In particular, little attention has been paid to the way in which a healthy reference population is to be selected, or the criteria for calculating the 99th URL value for cTn assays, thus highlighting the need for international recommendations not only for demographic and physiological variables criteria for defining a healthy reference population, but also for calculating mathematical algorithms for establishing/calculating clinical decision values. An expert consensus group, comprising laboratory and clinical scientists, biomedical statisticians, industrial and regulatory representatives, should be responsible for drawing up these guidelines.

Advances in Cardiac Biomarkers of Acute Coronary Syndrome

Acute coronary syndrome (ACS) encompasses a pathophysiological spectrum of cardiovascular diseases, all of which have significant morbidity and mortality. ACS was once considered an acute condition; however, new treatment strategies and improvements in biomarker assays have led to ACS being an acute and chronic disease. Cardiac troponin is the preferred biomarker for the diagnosis of myocardial infarction, and there is considerable interest and efforts toward development and implementation of high-sensitivity cardiac troponin (hs-cTn) assays worldwide. Analytical and clinical performance characteristics of hs-cTn assays as well as testing limitations are important for laboratorians and clinicians to understand in order to utilize testing appropriately. Furthermore, expanding the clinical utility of hs-cTn into other cohorts such as asymptomatic community dwelling populations, heart failure, and chronic kidney disease populations supports novel opportunities for improved short- and long-term prognosis.

Strategies to overcome misdiagnosis of type 1 myocardial infarction using high sensitive cardiac troponin assays

High sensitive cardiac troponin assays have become the gold standard in the diagnosis of an acute type 1 myocardial infarction (MI) in the absence of ST-segment elevation. Several acute or chronic conditions that impact cardiac troponin levels in the absence of a MI might lead to a misdiagnosis of MI. For example, patients with impaired renal function as well as elderly patients often present with chronically increased cardiac troponin levels. Therefore, the diagnosis of MI type 1 based on the 99th percentile upper limit of normal threshold is more difficult in these patients. Different diagnostic approaches might help to overcome this limitation of reduced MI specificity of sensitive troponin assays. First, serial troponin measurement helps to differentiate chronic from acute troponin elevations. Second, specific diagnostic cut-offs, optimized for a particular patient group, like elderly patients, are able to regain specificity. Such an individualized use and interpretation of sensitive cardiac troponin measurements improves diagnostic accuracy and reduces the amount of misdiagnosed MI type 1.

Reference Values and Release Kinetics of B-Type Natriuretic Peptide Signal Peptide in Patients with Acute Myocardial Infarction

BACKGROUND

The signal peptide for human B-type natriuretic peptide preprohormone (BNPsp), which is released from cardiomyocytes, is increased in plasma of patients with acute myocardial infarction (AMI); however, its exact release kinetics have not been defined.

METHODS

We measured BNPsp and high-sensitivity cardiac troponin T (hs-cTnT) in a reference group of individuals without structural heart disease (n = 285) and determined the release kinetics of these biomarkers in patients (n = 29) with hypertrophic obstructive cardiomyopathy undergoing transcoronary ablation of septal hypertrophy (TASH), a procedure allowing exact timing of onset of iatrogenic AMI. Blood samples were collected before TASH and at numerous preselected time points after TASH.

RESULTS

The reference median BNPsp concentration was 53.4 pmol/L [interquartile range (IQR) 47.0–61.0; 95th percentile 85.9 pmol/L; 99th percentile 116.3 pmol/L]. Baseline concentrations in patients undergoing TASH were higher than in the reference group [91.9 pmol/L (IQR 62.9–116.4); P &lt; 0.0001]. BNPsp increased significantly, peaking at 15 min after induction of AMI [149.6 pmol/L (109.5–204.9) vs baseline; P = 0.004] and declining slowly thereafter, falling below the preprocedural value after 8 h (P = 0.014). hs-cTnT increased significantly 15 min after induction of AMI [26 ng/L (19–39) vs 18 ng/L (11–29); P = 0.001] and remained high at all later time points.

CONCLUSIONS

BNPsp concentrations increased immediately after AMI induction, providing early evidence of myocardial injury. The release kinetics of BNPsp differed from those of hs-cTnT. These findings provide information that should help in establishing the diagnostic value of BNPsp in the setting of early AMI.

Sex-Specific Association of Sleep Apnea Severity With Subclinical Myocardial Injury, Ventricular Hypertrophy, and Heart Failure Risk in a Community-Dwelling Cohort: The Atherosclerosis Risk in Communities-Sleep Heart Health Study

BACKGROUND

Risk factors for obstructive sleep apnea (OSA) and the development of subsequent cardiovascular (CV) complications differ by sex. We hypothesize that the relationship between OSA and high-sensitivity troponin T (hs-TnT), cardiac structure, and CV outcomes differs by sex.

METHODS AND RESULTS

Seven hundred fifty-two men and 893 women free of CV disease participating in both the Atherosclerosis Risk in the Communities and the Sleep Heart Health Studies were included. All participants (mean age, 62.5 ± 5.5 years) underwent polysomnography and measurement of hs-TnT. OSA severity was defined by using established clinical categories. Subjects were followed for 13.6 ± 3.2 years for incident coronary disease, heart failure, and CV and all-cause mortality. Surviving subjects underwent echocardiography after 15.2 ± 0.8 years. OSA was independently associated with hs-TnT among women (P=0.03) but not in men (P=0.94). Similarly, OSA was associated with incident heart failure or death in women (P=0.01) but not men (P=0.10). This association was no longer significant after adjusting for hs-TnT (P=0.09). Among surviving participants without an incident CV event, OSA assessed in midlife was independently associated with higher left ventricle mass index only among women (P=0.001).

CONCLUSIONS

Sex-specific differences exist in the relationship between OSA and CV disease. OSA, assessed in midlife, is independently associated with higher levels of concomitantly measured hs-TnT among women but not men, in whom other comorbidities associated with OSA may play a more important role. During 13-year follow-up, OSA was associated with incident heart failure or death only among women, and, among those without an incident event, it was independently associated with left ventricular hypertrophy only in women.

Misdiagnosis of Myocardial Infarction Related to Limitations of the Current Regulatory Approach to Define Clinical Decision Values for Cardiac Troponin

BACKGROUND

Misdiagnosis of acute myocardial infarction (AMI) may significantly harm patients and may result from inappropriate clinical decision values (CDVs) for cardiac troponin (cTn) owing to limitations in the current regulatory process.

METHODS AND RESULTS

In an international, prospective, multicenter study, we quantified the incidence of inconsistencies in the diagnosis of AMI using fully characterized and clinically available high-sensitivity (hs) cTn assays (hs-cTnI, Abbott; hs-cTnT, Roche) among 2300 consecutive patients with suspected AMI. We hypothesized that the approved CDVs for the 2 assays are not biologically equivalent and might therefore contribute to inconsistencies in the diagnosis of AMI. Findings were validated by use of sex-specific CDVs and parallel measurements of other hs-cTnI assays. AMI was the adjudicated diagnosis in 473 patients (21%). Among these, 86 patients (18.2%) had inconsistent diagnoses when the approved uniform CDV was used. When sex-specific CDVs were used, 14.1% of female and 22.7% of male AMI patients had inconsistent diagnoses. Using biologically equivalent CDV reduced inconsistencies to 10% (P<0.001). These findings were confirmed with parallel measurements of other hs-cTn assays. The incidence of inconsistencies was only 7.0% for assays with CDVs that were nearly biologically equivalent. Patients with inconsistent AMI had long-term mortality comparable to that of patients with consistent diagnoses (P=NS) and a trend toward higher long-term mortality than patients diagnosed with unstable angina (P=0.05).

CONCLUSIONS

Currently approved CDVs are not biologically equivalent and contribute to major inconsistencies in the diagnosis of AMI. One of 5 AMI patients will receive a diagnosis other than AMI if managed with the alternative hs-cTn assay.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00470587.

A national survey of troponin testing and recommendations for improved practice

Background

The introduction of troponin assays with higher analytical sensitivity and enhanced performance has produced new challenges for both laboratory and clinician in the optimal investigation of patients with cardiovascular disease. After some years of collective experience with this new generation of assays, this survey aimed to assess the level of consensus that exists regarding their application.

Methods

A questionnaire was designed, based on a review of published evidence and current opinion, to obtain information on a number of key areas relating to troponin analysis and reporting and was circulated to lead laboratory consultants across the UK and Ireland.

Results

Completed questionnaires were received from 94 laboratory contacts. Sixty per cent of those who responded had implemented a high-sensitivity troponin assay, with the Roche Cobas troponin T high sensitivity assay the most widely used. It is evident that some confusion remains regarding the definition of high-sensitivity assays and there was considerable variation in practice, even among those using the same manufacturer’s assay.

Conclusions

There is a need for greater consensus in the approach to the clinical utilization of troponin assays with improved sensitivity and it is important that laboratories are fully aware of the capabilities of their assay and provide useful guidance to users. On the basis of survey findings and the existing evidence base, a number of recommendations have been proposed to improve current practice and enhance patient safety.

Decision limits and the reporting of cardiac troponin: Meeting the needs of both the cardiologist and the ED physician

Cardiac troponin is the preferred biomarker for defining the acute coronary syndrome and acute myocardial infarction. Currently, the only decision limit formally endorsed with regard to the cardiac troponins is the 99th percentile. This is a "rule-in" criterion, intended to ensure that only persons with the acute coronary syndrome are reviewed. The 99th percentile is an arbitrary cut point and there are many problems associated with its application, including defining a truly healthy population, the difficulty of standardisation of cardiac troponin assays, especially but not only cardiac troponin I, and the effects of age and sex on this parameter. The Emergency Department (ED) screens many more persons for possible acute coronary syndromes than actually have the condition and their needs are best met by a "rule-out" test that enables them to clear their busy departments of the many persons who do not actually have the condition. The needs of the ED are not optimally met using the 99th percentile. The index of individuality for the cardiac troponins is small and significant changes consistent with an acute coronary syndrome can occur without the 99th percentile being exceeded. It appears that the ED may be better served by use of delta troponin changes rather than the 99th percentile, but there are problems with this approach, particularly in persons who present late when troponin release has plateaued. In addition, there are many non-acute coronary syndrome causes for cardiac troponin release. The needs of the cardiologist and the ED physician are so different that it may be inappropriate for both groups to use the same diagnostic criteria for cardiac troponin, and it is of great importance that cardiac troponin measurement be used as only one part of the assessment of the person presenting with possible acute coronary syndrome.

Age- and sex-dependent upper reference limits for the high-sensitivity cardiac troponin T assay

OBJECTIVES

The study sought to determine the 99th percentile upper reference limit for the high-sensitivity cardiac troponin T assay (hs-cTnT) in 3 large independent cohorts.

BACKGROUND

The presently recommended 14 ng/l cut point for the diagnosis of myocardial infarction using the hs-cTnT assay was derived from small studies of presumably healthy individuals, with relatively little phenotypic characterization.

METHODS

Data were included from 3 well-characterized population-based studies: the Dallas Heart Study (DHS), the Atherosclerosis Risk in Communities (ARIC) Study, and the Cardiovascular Health Study (CHS). Within each cohort, reference subcohorts were defined excluding individuals with recent hospitalization, overt cardiovascular disease, and kidney disease (subcohort 1), and further excluding those with subclinical structural heart disease (subcohort 2). Data were analyzed stratified by age, sex, and race.

RESULTS

The 99th percentile values for the hs-cTnT assay in DHS, ARIC, and CHS were 18, 22, and 36 ng/l (subcohort 1) and 14, 21, and 28 ng/l (subcohort 2), respectively. These differences in 99th percentile values paralleled age differences across cohorts. Analyses within sex/age strata yielded similar results between cohorts. Within each cohort, 99th percentile values increased with age and were higher in men. More than 10% of men 65 to 74 years of age with no cardiovascular disease in our study had cardiac troponin T values above the current myocardial infarction threshold.

CONCLUSIONS

Use of a uniform 14 ng/l cutoff for the hs-cTnT assay may lead to over-diagnosis of myocardial infarction, particularly in men and the elderly. Clinical validation is needed of new age- and sex-specific cutoff values for this assay.

Association of multiple biomarkers and classical risk factors with early carotid atherosclerosis: results from the Gutenberg Health Study

BACKGROUND

In the Gutenberg Health Study, a random sample of the population was scanned with vascular ultrasound for early atherosclerosis. A continuous classical risk marker model (waist circumference, HbA1c, LDL/HDL ratio, pack years and pulse pressure) was compared to a model of modern biomarkers (C-reactive protein, troponin I, N-terminal pro B-type natriuretic peptide, copeptin, mid-regional pro-adrenomedullin, and asymmetric dimethylarginine) with regard to the ability of ruling out abnormal intima-media thickness (IMT), respectively, carotid plaques.

METHODS

Data of the first consecutive 5,000 participants (aged 35-74 years; 2,540 men, 2,460 women) were analyzed. IMT was measured at both common carotid arteries using an edge detection system. Plaques were defined as protrusion of ≥1.5 mm in common, internal and external carotid artery.

RESULTS

For classical risk factors, in comparison to a model of six modern biomarkers, regarding the variable (a) IMT>0.85 mm negative and positive predictive value (NPV and PPV) were 0.98 and 0.16 for both the classical risk factor model and the biomarker model. The second variable (b) presence of plaque could be ruled out with an NPV of 0.84 and identified with a PPV of 0.61 for classical risk factors, and 0.84 and 0.58 for biomarkers, respectively. Values were calculated using logistic regression analysis.

CONCLUSION

Classical risk factors allow ruling out pathologic IMT and presence of carotid plaques in a population of primary prevention in a reliable way. Modern biomarkers performed almost equally well but did not provide further information.