Defining normality in a European multinational cohort: Critical factors influencing the 99th percentile upper reference limit for high sensitivity cardiac troponin I

Prognostic significance of chronic myocardial injury diagnosed by three different cardiac troponin assays in patients admitted with suspected acute coronary syndrome

OBJECTIVES

Chronic myocardial injury (CMI) is defined as stable concentrations of cardiac troponin T or I (cTnT or cTnI) above the assay-specific 99th percentile upper reference limit (URL) and signals poor outcome. The clinical implications of diagnosing CMI are unclear. We aimed to assess prevalence and association of CMI with long-term prognosis using three different high-sensitivity cTn (hs-cTn) assays.

METHODS

A total of 1,292 hospitalized patients without acute myocardial injury had cTn concentrations quantified by hs-cTn assays by Roche Diagnostics, Abbott Diagnostics and Siemens Healthineers. The median follow-up time was 4.1 years. The prevalence of CMI and hazard ratios for mortality and cardiovascular (CV) events were calculated based on the URL provided by the manufacturers and compared to the prognostic accuracy when lower percentiles of cTn (97.5, 95 or 90), limit of detection or the estimated bioequivalent concentrations between assays were used as cutoff values.

RESULTS

There was no major difference in prognostic accuracy between cTnT and cTnI analyzed as continuous variables. The correlation between cTnT and cTnI was high (r=0.724-0.785), but the cTnT assay diagnosed 3.9-4.5 times more patients with having CMI based on the sex-specific URLs (TnT, n=207; TnI Abbott, n=46, TnI Siemens, n=53) and had higher clinical sensitivity and AUC at the URL.

CONCLUSIONS

The prevalence of CMI is highly assay-dependent. cTnT and cTnI have similar prognostic accuracy for mortality or CV events when measured as continuous variables. However, a CMI diagnosis according to cTnT has higher prognostic accuracy compared to a CMI diagnosis according to cTnI.

Distribution and prognostic value of high-sensitivity cardiac troponin T and I across glycemic status: a population-based study

BACKGROUND

Whether distributions and prognostic values of high-sensitivity cardiac troponin (hs-cTn) T and I are different across normoglycemic, prediabetic, and diabetic populations is unknown.

METHODS

10127 adult participants from the National Health and Nutrition Examination Survey 1999-2004 with determined glycemic status and measurement of at least one of hs-cTn assays were included, from whom healthy participants and presumably healthy diabetic and prediabetic participants were selected to investigate pure impacts of glycemic status on distributions of hs-cTn. The nonparametric method and bootstrapping were used to derive the 99th upper reference limits of hs-cTn and 95% CI. Participants with available follow-up and hs-cTn concentrations of all 4 assays were included in prognostic analyses. Associations of hs-cTn with all-cause and cardiac-specific mortality were modeled by Cox proportional hazard regression under the complex survey design. The incremental value of hs-cTn to an established risk score in predicting cardiac-specific mortality was assessed by the 10-year area under time-dependent receiver operating characteristic curve (AUC) using the Fine-Grey competing risk model.

RESULTS

Among 9714 participants included in prognostic analyses, 5946 (61.2%) were normoglycemic, 2172 (22.4%) prediabetic, and 1596 (16.4%) diabetic. Hyperglycemic populations were older than the normoglycemic population but sex and race/ethnicity were similar. During the median follow-up of 16.8 years, hs-cTnT and hs-cTnI were independently associated with all-cause and cardiac-specific mortality across glycemic status. In the diabetic population, adjusted hazard ratios per 1-standard deviation increase of log-transformed hs-cTnT and hs-cTnI (Abbott) concentrations were 1.77 (95% CI 1.48-2.12; P < .001) and 1.83 (95% CI 1.33-2.53; P < .001), respectively, regarding cardiac-specific mortality. In the diabetic but not the normoglycemic population, adding either hs-cTnT (difference in AUC: 0.062; 95% CI 0.038-0.086; P < 0.001) or hs-cTnI (Abbott) (difference in AUC: 0.071; 95% CI 0.046-0.097; P < 0.001) would significantly increase the discriminative ability of the risk score; AUC of the score combined with hs-cTnT would be further improved by incorporating hs-cTnI (0.018; 95%CI 0.006-0.029; P = 0.002). The 99th percentile of hs-cTnT of the presumably healthy diabetic population was higher than the healthy population and had no overlap in 95% CIs, however, for hs-cTnI 99th percentiles of the two populations were very close and 95% CIs extensively overlapped.

CONCLUSIONS

Hs-cTnT and hs-cTnI demonstrated consistent prognostic associations across glycemic status but incremental predictive values in hyperglycemic populations only. The susceptibility of hs-cTnT 99th percentiles to diabetes plus the additive value of hs-cTnI to hs-cTnT in diabetic cardiovascular risk stratification suggested hs-cTnI and hs-cTnT may be differentially associated with glycemic status, but further research is needed to illustrate the interaction between hyperglycemia and hs-cTn.

Myocardial Injury Thresholds for 4 High-Sensitivity Troponin Assays in a Population-Based Sample of US Children and Adolescents

BACKGROUND

Myocardial injury is an important pediatric diagnosis. Establishing normative data from a representative pediatric sample is vital to provide accurate upper reference limits (URLs) for defining myocardial injury using high-sensitivity cardiac troponin.

METHODS

Among participants 1 to 18 years of age in the 1999-2004 National Health and Nutrition Examination Survey, we measured high-sensitivity troponin T using one assay (Roche) and high-sensitivity troponin I using 3 assays (Abbott, Siemens, and Ortho). In a strictly defined healthy subgroup, we estimated 97.5th and 99th percentile URLs for each assay using the recommended nonparametric method.

RESULTS

Of 5695 pediatric participants, 4029 met criteria for the healthy subgroup (50% males; mean age 12.6 years). Our 99th percentile URL estimates for all 4 high-sensitivity troponin assays among children and adolescents were lower than the manufacturer-reported URLs (derived from adults). The 99th percentile URLs (95% CI) were 15 ng/L (95% CI, 12-17) for high-sensitivity troponin T, 16 ng/L (95% CI, 12-19) for high-sensitivity troponin I with the Abbott assay, 38 ng/L (95% CI, 25-46) for high-sensitivity troponin I with the Siemens assay, and 7 ng/L (95% CI, 5, 12) for high-sensitivity troponin I with the Ortho assay. The 95% CIs for age-, sex-, and race and ethnicity-specific 99th percentile URLs overlapped. However, the 97.5th percentile URL for each assay was measured with superior statistical precision (ie, tighter 95% CIs) and demonstrated differences by sex. For male compared with female children and adolescents, 97.5th percentile URLs were 11 ng/L (95% CI, 10-12) versus 6 ng/L (95% CI, 6-7) for high-sensitivity troponin T, 9 ng/L (95% CI, 7-10) versus 5 ng/L (95% CI, 4-6) for high-sensitivity troponin I with the Abbott assay, 21 ng/L (95% CI, 18-25) versus 11 ng/L (95% CI, 9-13) for high-sensitivity troponin I with the Siemens assay, and 4 ng/L (95% CI, 3-5) versus 2 ng/L (95% CI, 1-3) for high-sensitivity troponin I with the Ortho assay. In contrast to the 99th percentiles, the point estimates of 97.5th percentile pediatric URLs for high-sensitivity troponin were also much more stable to differences in the analytic approaches taken to estimate URLs.

CONCLUSIONS

Because myocardial infarction is rare in children and adolescents, the use of statistically more precise and reliable sex-specific 97.5th percentile high-sensitivity troponin URLs might be considered to define pediatric myocardial injury.

Using logistic regression models to investigate the effects of high-sensitivity cardiac troponin T confounders on ruling in acute myocardial infarction

OBJECTIVES

Confounding factors, including sex, age, and renal dysfunction, affect high-sensitivity cardiac troponin T (hs-cTnT) concentrations and the acute myocardial infarction (AMI) diagnosis. This study assessed the effects of these confounders through logistic regression models and evaluated the diagnostic performance of an optimized, integrated prediction model.

METHODS

This retrospective study included a primary derivation cohort of 18,022 emergency department (ED) patients at a US medical center and a validation cohort of 890 ED patients at a Canadian medical center. Hs-cTnT was measured with 0/3 h sampling. The primary outcome was index AMI diagnosis. Logistic regression models were optimized to predict AMI using delta hs-cTnT and its confounders as covariates. The diagnostic performance of model cutoffs was compared to that of the hs-cTnT delta thresholds. Serial logistic regressions were carried out to evaluate the relationship between covariates.

RESULTS

The area under the curve of the best-fitted model was 0.95. The model achieved a 90.0% diagnostic accuracy in the validation cohort. The optimal model cutoff yielded comparable performance (90.5% accuracy) to the optimal sex-specific delta thresholds (90.3% accuracy), with 95.8% agreement between the two diagnostic methods. Serial logistic regressions revealed that delta hs-cTnT played a more predominant role in AMI prediction than its confounders, among which sex is more predictive of AMI (total effect coefficient 1.04) than age (total effect coefficient 0.05) and eGFR (total effect coefficient -0.008).

CONCLUSIONS

The integrated prediction model incorporating confounding factors does not outperform hs-cTnT delta thresholds. Sex-specific hs-cTnT delta thresholds remain to provide the highest diagnostic accuracy.

Variability of cardiac troponin levels in normal subjects and in patients with cardiovascular diseases: analytical considerations and clinical relevance

In accordance with all the most recent international guidelines, the variation of circulating levels of cardiac troponins I and T, measured with high-sensitivity methods (hs-cTnI and hs-cTnT), should be used for the detection of acute myocardial injury. Recent experimental and clinical evidences have demonstrated that the evaluation of hs-cTnI and hs-cTnT variations is particularly relevant: a) for the differential diagnosis of Acute Coronary Syndromes (ACS) in patients admitted to the Emergency Department (ED); b) for the evaluation of cardiovascular risk in patients undergoing major cardiac or non-cardiac surgery, and in asymptomatic subjects of the general population aged >55 years and with co-morbidities; c) for the evaluation of cardiotoxicity caused by administration of some chemotherapy drugs in patients with malignant tumors. The aim of this document is to discuss the fundamental statistical and biological considerations on the intraindividual variability of hs-cTnI and hs-cTnT over time in the same individual. Firstly, it will be discussed in detail as the variations of circulating levels strictly depend not only on the analytical error of the method used but also on the intra-individual variability of the biomarker. Afterwards, the pathophysiological interpretation and the clinical relevance of the determination of the variability of the hs-cTnI and hs-cTnT values ​​ in patients with specific clinical conditions are discussed. Finally, the evaluation over time of the variation in circulating levels of hs-cTnI and hs-cTnT is proposed for a more accurate estimation of cardiovascular risk in asymptomatic subjects from the general population.

Myocardial Injury Thresholds for 4 High-Sensitivity Troponin Assays in U.S. Adults

BACKGROUND

Myocardial injury is currently defined as a cardiac troponin above the sex-specific 99th percentile of a healthy reference population (upper reference limit [URL]).

OBJECTIVES

The purpose of this study was to estimate high-sensitivity (hs) troponin URLs in a representative sample of the U.S. adult population; overall and by sex, race/ethnicity, and age group.

METHODS

Among adults participating in the 1999-2004 National Health and Nutrition Examination Survey (NHANES), we measured hs-troponin T using 1 assay (Roche) and hs-troponin I using 3 assays (Abbott, Siemens, and Ortho). In a strictly defined healthy reference subgroup, we estimated 99th percentile URLs for each assay using the recommended nonparametric method.

RESULTS

Of 12,545 participants, 2,746 met criteria for the healthy subgroup (mean age 37 years, 50% men). The NHANES 99th percentile URL for hs-troponin T (19 ng/L) matched the manufacturer-reported URL (19 ng/L). NHANES URLs were 13 ng/L (95% CI: 10-15 ng/L) for Abbott hs-troponin I (manufacturer: 28 ng/L), 5 ng/L (95% CI: 4-7 ng/L) for Ortho hs-troponin I (manufacturer: 11 ng/L), and 37 ng/L (95% CI: 27-66 ng/L) for Siemens hs-troponin I (manufacturer: 46.5 ng/L). There were significant differences in URLs by sex, but none by race/ethnicity. Furthermore, the 99th percentile URLs for all 4 hs-troponin assays were statistically significantly lower in healthy adults aged <40 years compared with healthy adults ≥60 years (all P < 0.001 by rank sum testing).

CONCLUSIONS

We found URLs for hs-troponin I assays that were substantially lower than currently listed 99th percentile URLs. There were significant differences in hs-troponin T and I URLs by sex and by age group in healthy U.S. adults but none by race/ethnicity.

A comparison of echocardiographic and circulating cardiac biomarkers for predicting incident cardiovascular disease

Background

Echocardiographic measures are known predictors of cardiovascular disease (CVD) in the general population. This study compared the predictive value of such measures to that of circulating cardiac biomarkers for a composite cardiovascular disease outcome in an aging population.

Methods

In this prospective population-based cohort study, echocardiography was performed at baseline together with assessments of traditional CVD risk factors and circulating cardiac biomarkers, NT-proBNP and troponin I, in 1016 individuals all aged 70 years. Assessments were repeated at ages 75 and 80. A composite CVD outcome (myocardial infarction, heart failure or ischemic stroke) was charted over 15 years. All echocardiography variables, except for the E/A ratio, were analyzed on a continuous scale.

Results

Over 10 years, left atrial (LA) diameter, left ventricular mass index (LVMI) and high E/A ratio (>1.5) increased, while left ventricular ejection fraction (LVEF) remained unchanged. Using Cox proportional hazard analyses with time-updated variables for echocardiographic measures and traditional risk factors, an enlarged LA diameter and a low LVEF were independently related to incident CVD in 222 participants. The addition of LA diameter and LVEF to traditional risk factors increased the C-statistic by 1.5% (p = 0.008). However, the addition of troponin I and NT-proBNP to traditional risk factors increased the C-statistic by 3.0% (p<0.001).

Conclusion

An enlarged LA diameter and a low LVEF improved the prediction of incident CVD compared to traditional risk factors. However, given that troponin I and NT-proBNP improved prediction to a similar extent, the use of simple blood tests to improve clinical cardiovascular disease risk prediction is only further supported by this study.

High-sensitivity cardiac troponin I: is ethnicity relevant?

AIMS

To evaluate 99th percentile upper reference limits (URLs) and investigate ethnic differences for the Abbott Architect high-sensitivity cardiac troponin I (hs-cTnI) in a middle-aged to elderly cosmopolitan population.

METHODS

In subjects without cardiovascular disease and after outlier exclusion, data on hs-cTnI from 149 white men, 150 white women, 150 South Asian (SA) men and 150 SA women in their sixth, seventh and eight decades were analysed. Each ethnicity-gender-decade subgroup consisted of 50 patients except white men in their sixth decade (n=49).

RESULTS

The overall, women and men hs-cTnI 99th percentile URLs were 22.1, 17.9 and 24.8 ng/L, respectively. Median (IQR) hs-cTnI was higher in men (2.7 (1.8-4.1) ng/L) than in women (1.9 (1.1-3.2) ng/L; p<0.001). White men (3.2 (2.2-4.4) ng/L) had higher hs-cTnI than SA men (2.5 (1.6-3.6) ng/L; p<0.001), white women (2.1 (1.3-3.3) ng/L; p<0.001) and SA women (1.6 (1.0-3.0) ng/L; p<0.001). Hs-cTnI in white women was similar to SA women (p=0.07) and SA men (p=0.07). Patients in the eighth decade had higher hs-cTnI (p<0.05) than those in sixth decade within each ethnicity-gender subgroup. Of significant associations, age had the greatest impact on hs-cTnI followed by gender and then ethnicity.

CONCLUSION

We report white-SA differences in hs-cTnI in men and a similar trend in women. We confirm age and gender differences in hs-cTnI, irrespective of ethnicity. Further studies are required to determine whether ethnicity-specific age and gender 99th percentile URLs improve detection or exclusion of myocardial injury.

[Diagnostic value of high-sensitivity troponin I to predict cardiac causes after syncope/near syncope in emergency department]

AIMS

The objective of this study is to evaluate the diagnostic accuracy of high-sensitivity (hs) troponin I to predict cardiac origin after syncope. The secondary objective is to determine the causes of elevated troponin.

PROCEDURE

Were included hospitalized patients with syncope/near syncope diagnosed in ED. The diagnostic accuracy to predict cardiac origin was evaluated and compared to the "high risk" group, defined by the 2018 European Society of Cardiology guidelines.

RESULTS

A total of 163 patients were enrolled, 26% had a cardiac origin. Positive troponin I hs predict a cardiac origin with a sensitivity of 31%, a specificity of 80%, positive predictive value of 35% and negative value of 77%. These diagnostic performances are not discriminating and lower than the ESC classification. A positive troponine I hs level is associated with 5 times more cardiac failure during the hospitalization.

CONCLUSION

A positive troponin I hs level after syncope/near syncope is not predictive of cardiac origin. It appears to be an early marker of ventricular remodeling in heart failure.

Determination of high sensitive cardiac troponin I 99th percentile upper reference limits in a healthy Pakistani population

OBJECTIVE

This study aims to establish the 99^th percentile upper reference limits of high sensitive cardiac troponin I in a healthy Pakistani population.

METHODS

It was an Observational cohort study carried out in Department of Chemical Pathology and Endocrinology Rehman Medical Institute Peshawar, over the period of one year (January 2019- December 2019). Total 299 cardio-healthy males and females were interviewed and taken past medical history. Based on history, clinical examination, echocardiogram and laboratory data including results of estimated glomerular filtration rate (eGFR) and N-terminal pro-B-type natriureteric peptide (NT-proBNP), subjects with possible subclinical diseases were excluded. High Sensitive Cardiac Troponin I (hs-cTtrop I) was analysed on Abbot ARCHITECT STAT ci8200 using chemiluminescent immunoassay technique. The 99th percentile upper reference limit (URL) of hs-cTtrop I was determined using a non-parametric statistic, while gender specific results were compared.

RESULTS

In this study, 178 males (59.5%) and 121 females (40.5%) were included. The median Interquartile ranges (IQR) of age was 57 (11.6) for males and 56 (13) for females. The 99th percentile URL hs-cTtrop I was found to be 33.9 ng/L, while gender specific values were 38.41ng/L and 15.73ng/L for males and females, respectively (p= 0.0045).

CONCLUSION

High sensitivity cardiac troponin I 99th percentile URL in our study population was found to be 33.9 ng/L with gender specific values being 38.41 ng/L and 15.73ng/L for males and females respectively. Troponin I in males was substantially high in comparison with females.

High-Sensitivity Cardiac Troponin I Improves Cardiovascular Risk Prediction in Older Men: HIMS (The Health in Men Study)

Background

The Framingham Risk Score estimates the 10‐year risk of cardiovascular events. However, it performs poorly in older adults. We evaluated the incremental benefit of adding high‐sensitivity cardiac troponin I (hs‐cTnI) to the Framingham Risk Score.

Methods and Results

The HIMS (Health in Men Study) is a cohort study of community‐dwelling men aged 70 to 89 years in Western Australia. Participants were identified from the electoral roll, with a subset undergoing plasma analysis. Hs‐cTnI (Abbott Architect i2000SR) was measured in 1151 men without prior cardiovascular disease. The Western Australia Data Linkage System was used to identify incident cardiovascular events. After 10 years of follow‐up, 252 men (22%) had a cardiovascular event (CVE+) and 899 did not (CVE–). The Framingham Risk Score placed 148 (59%) CVE+ and 415 (46%) CVE– in the high‐risk category. In CVE– men, adding hs‐cTnI affected the risk categories of 244 (27.2%) men, with 64.8% appropriately reclassified to a lower and 35.2% to a higher category, which decreased the number of high‐risk men in the CVE– to 39%. In CVE+ men, adding hs‐cTnI affected the risk categories of 61 (24.2%), with 50.8% appropriately reclassified to a higher and 49.2% to a lower category and 82.5% remaining above the 15% risk treatment threshold. The net reclassification index was 0.305 (P<0.001). Adding hs‐cTnI increased the C‐statistic modestly from 0.588 (95% CI, 0.552–0.624) to 0.624 (95% CI, 0.589–0.659) and improved model fit (likelihood ratio test, P<0.001).

Conclusions

Adding hs‐cTnI to the Framingham Risk Score provided incremental prognostic benefit in older men, especially aiding reclassification of individuals into a lower risk category.

Highly Sensitive Cardiac Troponins: The Evidence Behind Sex-Specific Cutoffs

Emergence of various highly sensitive cardiac troponin assays into clinical practice provides a new tool for clinicians diagnosing acute coronary syndrome. These assays also create a challenge for laboratories and clinicians who have yet to familiarize themselves with sex-specific cutoffs. Healthy men and women, studied across various age groups and geographic locations, have notable differences in baseline values of highly sensitive cardiac troponin I and T, leading to establishment of sex-specific upper reference limits and cutoffs. Several differences in cardiac physiology, size, and structure may account for baseline differences in highly sensitive cardiac troponins and outcomes between the sexes. The clinical utility of implementing sex-specific cutoffs for diagnosis and management of acute coronary syndrome remains unclear. Presently, the only prospective study failed to show improved outcomes for men or women with use of sex-specific cutoffs; however, a major limitation is the frequent lack of diagnostic, therapeutic, and preventive interventions prescribed to women with low-level troponin elevations. Based on the current literature, we posit that there may nonetheless be clinical value in the use of sex-specific cutoffs for evaluating suspected acute coronary syndrome, especially in select patient populations such as younger women who tend to have lower baseline values of highly sensitive cardiac troponins. Future studies should prospectively evaluate differences in diagnostic, pharmacologic, and interventional management in men and women using myocardial infarctions classified with sex-specific cutoffs of the highly sensitive cardiac troponin assays.

A study of biological and lifestyle factors, including within-subject variation, affecting concentrations of growth differentiation factor 15 in serum

Background Growth differentiation factor 15 (GDF-15) is an emerging cardiovascular biomarker, and a fully automated immunoassay has recently become available. The objectives of the study were to identify biological and lifestyle factors affecting serum GDF-15 concentrations and derive robust reference intervals, and to estimate GDF-15 within-subject biological variation and derived indices. Methods A presumably healthy population of 533 questionnaire-screened adults was used to identify the biological and lifestyle determinants of serum GDF-15. Following stringent exclusion criteria, a final group of 173 individuals was selected to establish GDF-15 reference interval. Twenty-six healthy volunteers were enrolled in the biological variation substudy. Results Using a multiple regression model, age, B-type natriuretic peptide and C-reactive protein as well as smoking status were significantly related to serum GDF-15 concentrations. The upper reference limit (URL) for serum GDF-15 concentrations (90% confidence interval [CI]) was 866 ng/L (733-999 ng/L), with no sex-related difference. Although GDF-15 tended to increase with age, the weak dependence of marker from age does not justify age-related URL. The within-subject CV was 6.3% (95% CI, 4.5%-8.5%), with no sex difference in intraindividual variances. The reference change value (RCV) for GDF-15 was 23%, and two are the specimens required to ensure that the mean GDF-15 result is within ±10% of the individual's homeostatic set point. Conclusions By identifying the main factors influencing serum GDF-15 concentrations, we robustly established the URL to be applied in adult population. As intraindividual variation of GDF-15 is relatively low, monitoring longitudinal changes in its concentrations over time using RCV can be a good alternative for interpreting GDF-15 in clinical setting.

Determination of high-sensitivity cardiac troponin T upper reference limits under the improved selection criteria in a Chinese population

BACKGROUND

There is no common consensus on how to define the reference population for determination of high-sensitivity cardiac troponin (hs-cTn) upper reference limit (URL). This study aimed to establish 99th percentile URLs of hs-cTnT under both 2018 AACC/IFCC criteria and improved selection criteria for further judging whether two URLs are different.

METHODS

Applying the stratified cluster sampling protocol, this study took 1848 apparently healthy subjects in communities of Shenyang China as the screening objects. We first followed 2018 AACC/IFCC criteria using surrogate biomarker for diabetes, myocardial dysfunction, renal dysfunction, and electrocardiogram. Then, we followed improved selection criteria to exclude hypertension, overweight and obesity, and dyslipidemia by physical examination and laboratory screening. Accordingly, 99th percentile URLs of hs-cTnT were established.

RESULTS

If the 2018 AACC/IFCC criteria were applied, 99th percentile URLs (90% confidence interval) of hs-cTnT male, female, and total were 19 (17-20) ng/L, 16 (15-17) ng/L, and 18 (16-19) ng/L, respectively. If added a single supplementary selection criteria, 99th percentile URLs of hs-cTnT total reduced to 16 ng/L, 17 ng/L, and 16 ng/L, respectively. If the improved selection criteria were applied, 99th percentile URLs (90% confidence interval) of hs-cTnT male, female, and total were 18 (14-24) ng/L, 13 (11-16) ng/L, and 16 (13-17) ng/L, respectively. The 99th percentile URLs of hs-cTnT male were higher than those of female in every age group.

CONCLUSIONS

Improved selection criteria through questionnaire survey, physical examination, and laboratory screening to further exclude hypertension, overweight and obesity, and dyslipidemia can avoid overestimation of the 99th percentile URL of hs-cTnT.

Plasma midregional proadrenomedullin (MR-proADM) concentrations and their biological determinants in a reference population

BACKGROUND

Midregional proadrenomedullin (MR-proADM) is emerging as a prognostic biomarker for detecting the failure of multiple organs. Establishment of scientifically robust reference intervals facilitates interpretation of laboratory test results. The objectives of this study were (i) to establish reliable reference intervals for plasma MR-proADM using a commercially available automated fluoroimmunoassay in apparently healthy individuals, and (ii) to identify biological determinants of MR-proADM concentrations.

METHODS

A total of 506 questionnaire-identified apparently healthy adults were enrolled in a single-center, cross-sectional study. A final reference group (n=172) was selected after exclusion of obese individuals, those with increased values of laboratory biomarkers indicating asymptomatic myocardial injury or dysfunction, ongoing inflammation, diabetes, dyslipidemia and renal dysfunction and outliers.

RESULTS

The 2.5th and 97.5th percentile intervals for MR-proADM values in the reference group (90% confidence interval) were 0.21 (0.19-0.23) and 0.57 (0.55-0.59) nmol/L, respectively. Although older age, higher values of HbA1c, C-reactive protein, B-type natriuretic peptide and body mass index, together with a history of smoking and a decreased estimated glomerular filtration rate were significantly associated with increasing concentrations of MR-proADM in both univariate and multivariate analyses, magnitudes of these relationships were modest and did not substantially influence MR-proADM reference intervals. Sex-dependent difference in MR-proADM reference intervals was not detected [0.19 (0.16-0.22)-0.56 (0.54-0.60) nmol/L in females vs. 0.22 (0.20-0.25)-0.58 (0.57-0.63) nmol/L in males].

CONCLUSIONS

Our study successfully established robust reference intervals for MR-proADM concentrations in plasma. Considering the negligible influence of potential biological determinants on plasma MR-proADM, we recommend the adoption of single reference intervals for adult population as a whole.

Sex-Specific Cut-Offs for High-Sensitivity Cardiac Troponin: Is Less More?

Management of patients presenting to the Emergency Department with chest pain is continuously evolving. In the setting of acute coronary syndrome, the availability of high-sensitivity cardiac troponin assays (hs-cTn) has allowed for the development of algorithms aimed at rapidly assessing the risk of an ongoing myocardial infarction. However, concerns were raised about the massive application of such a simplified approach to heterogeneous real-world populations. As a result, there is a potential risk of underdiagnosis in several clusters of patients, including women, for whom a lower threshold for hs-cTn was suggested to be more appropriate. Implementation in clinical practice of sex-tailored cut-off values for hs-cTn represents a hot topic due to the need to reduce inequality and improve diagnostic performance in females. The aim of this review is to summarize current evidence on sex-specific cut-off values of hs-cTn and their application and usefulness in clinical practice. We also offer an extensive overview of thresholds reported in literature and of the mechanisms underlying such differences among sexes, suggesting possible explanations about debated issues.

Predictors of 10-year changes in levels of N-terminal pro B-type natriuretic peptide and cardiac troponin I in the elderly

BACKGROUND

Measurement of N-terminal pro B-type natriuretic peptide (NT-proBNP) and cardiac troponin I (cTnI) might be useful for monitoring of cardiovascular disease in the elderly. However, it is not clear whether changes in these biomarkers are associated with changes in the cardiovascular risk profile and if this pattern could be modified by changes in lifestyle habits or medications.

METHODS

We measured levels of NT-proBNP and cTnI in community-dwelling subjects (PIVUS study) upon visits scheduled at age 70 (n=1007), 75 (n=825) and 80 (n=602). The associations of these biomarkers with repeated measurements of clinical variables (risk factors, lifestyle habits, echocardiographic data and medications) were investigated using sex-adjusted linear mixed random effect models.

RESULTS

NT-proBNP and cTnI were positively associated with increasing age. NT-proBNP, but not cTnI, was affected by changes of renal function and the degree of obesity. NT-proBNP was more closely related than cTnI to changes in echocardiographic estimates of cardiac geometry and function. Biomarker levels and/or their changes were inversely associated with a physically more active lifestyle (both NT-proBNP and cTnI) and statin treatment at age 70 (only cTnI). Changes in smoking status or antihypertensive treatment had no effect on biomarker levels.

CONCLUSIONS

Changes in NT-proBNP and cTnI levels are associated with different patterns of cardiovascular disease burden when using a longitudinal approach. However, levels of both biomarkers and their changes also reflect changes in the cardiovascular risk profile that might be modifiable. This is an important aspect for the use of any cardiovascular biomarker in an elderly population.

Sex differences in ischemic heart disease and heart failure biomarkers

Since 1984, each year, more women than men die of ischemic heart disease (IHD) and heart failure (HF), yet more men are diagnosed. Because biomarker assessment is often the first diagnostic employed in such patients, understanding biomarker differences in men vs. women may improve female morbidity and mortality rates.

Some key examples of cardiac biomarker utility based on sex include contemporary use of “unisex” troponin reference intervals under-diagnosing myocardial necrosis in women; greater use of hsCRP in the setting of acute coronary syndrome (ACS) could lead to better stratification in women; and greater use of BNP with sex-specific thresholds in ACS could also lead to more timely risk stratification in women.

Accurate diagnosis, appropriate risk management, and monitoring are key in the prevention and treatment of cardiovascular diseases; however, the assessment tools used must also be useful or at least assessed for utility in both sexes. In other words, going forward, we need to evaluate sex-specific reference intervals or cutoffs for laboratory tests used to assess cardiovascular disease to help close the diagnostic gap between men and women.

Distinguishing reference intervals and clinical decision limits - A review by the IFCC Committee on Reference Intervals and Decision Limits

Reference Intervals (RIs) and clinical decision limits (CDLs) are a vital part of the information supplied by laboratories to support the interpretation of numerical clinical pathology results. RIs describe the typical distribution of results seen in a healthy reference population while CDLs are associated with a significantly higher risk of adverse clinical outcomes or are diagnostic for the presence of a specific disease. However, as the two concepts are sometimes confused, there is a need to clarify the differences between these terms and to ensure they are easily distinguished, especially because CDLs have a clinical association with specific diseases and risks, thereby implying that effective clinical interventions are available. It is important to note that, because population-based RIs are derived from the range of values expected in a typical community population, laboratory results that fall outside a RI do not necessarily indicate a disease but rather that additional medical follow-up and/or treatment may be warranted. In contrast, CDLs are associated with a risk of specific adverse outcomes, and are commonly used to interpret laboratory test results, including lipid parameters, glucose, hemoglobin A1c (HbA1c), and tumor markers, to determine risk of disease, to diagnose or to treat. In recent years, the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) Committee on Reference Intervals and Decision Limits (C-RIDL) has focused primarily on RIs and has performed multicenter studies to obtain common RIs. However, the broader responsibility of the Committee, from its name, includes "decision limits". C-RIDL now aims to emphasize the importance of the correct use of both RIs and CDLs and to encourage laboratories to specify the appropriate information to clinicians as needed. This review discusses RIs and CDLs in detail, describes the similarities and the differences between these two important tools in laboratory medicine, and clearly explains the processes used to define them. C-RIDL encourages the involvement of laboratory professionals in the establishment of both RIs and CDLs.

Sex-Specific Versus Overall Clinical Decision Limits for Cardiac Troponin I and T for the Diagnosis of Acute Myocardial Infarction: A Systematic Review

BACKGROUND

The overall clinical decision limits of high-sensitivity cardiac troponin I (hs-cTnI; 26 ng/L) and T (hs-cTnT; 14 ng/L) may contribute to underdiagnosis of acute myocardial infarction in women. We performed a systematic review to investigate sex-specific and overall 99th percentiles of hs-cTnI and hs-cTnT derived from healthy reference populations.

CONTENT

We searched in PubMed and EMBASE for original studies, and by screening reference lists. Reference populations designed to establish 99th percentiles of hs-cTnI (Abbott) and/or hs-cTnT (Roche), published between January 2009 and October 2017, were included. Sex-specific and overall 99th percentile values of hs-cTnI and hs-cTnT were compared with overall clinical decision ranges (hs-cTnI, 23-30 ng/L; hs-cTnT, 13-25 ng/L). Twenty-eight studies were included in the systematic review. Of 16 hs-cTnI and 18 hs-cTnT studies, 14 (87.5%) and 11 (61.1%) studies reported lower female-specific hs-cTn cutoffs than overall clinical decision ranges, respectively. Conversely, male-specific thresholds of both hs-cTnI and hs-cTnT were in line with currently used overall thresholds, particularly hs-cTnT (90% concordance). The variation of estimated overall 99th percentiles was much higher for hs-cTnI than hs-cTnT (29.4% vs 80.0% of hs-cTnI and hs-cTnT studies reported values within the current overall clinical decision range, respectively).

SUMMARY

Our data show substantially lower female-specific upper reference limits of hs-cTnI and hs-cTnT than overall clinical decision limits of 26 ng/L and 14 ng/L, respectively. The statistical approach strongly affects the hs-cTnI threshold. Downward adjustment of hs-cTn thresholds in women may be warranted to reduce underdiagnosis of acute myocardial infarction in women.

Analytical evaluation of the new Beckman Coulter Access high sensitivity cardiac troponin I immunoassay

BACKGROUND

This study was aimed to evaluate the analytical performance of the novel chemiluminescent and fully-automated Beckman Coulter Access hsTnI high-sensitivity immunoassay for measurement of cardiac troponin I (cTnI).

METHODS

The study, using lithium heparin samples, included assessment of limit of blank (LOB), limit of detection (LOD), functional sensitivity, linearity, imprecision (within run, between-run and total), calculation of 99th percentile upper reference limit (URL) in 175 healthy blood donors (mean age, 36±12 years; 47% women) and comparison with two other commercial cTnI immunoassays.

RESULTS

The LOB, LOD and functional sensitivity of Access hsTnI were 0.14, 0.34 and 1.35 ng/L, respectively. The within-run, between-run and total imprecision was 2.2%-2.9%, 4.6%-5.4%, and 5.4%-6.1%, respectively. The linearity was excellent in the range of cTnI values between 0.95 and 4195 ng/L (r=1.00). The 99th percentile URL was 15.8 ng/L. Measurable cTnI values were found in 173/175 healthy subjects (98.9%). Good agreement of cTnI values was found with AccuTnI+3 (r=0.97; mean bias, -9.3%), whereas less satisfactory agreement was found with Siemens Dimension Vista cTnI (r=0.95; mean bias, -55%).

CONCLUSIONS

The results of our evaluation of the Beckman Coulter Access hsTnI indicate that the analytical performance of this fully-automated immunoassay is excellent.

Diagnostic performance of point-of-care and central laboratory cardiac troponin assays in an emergency department

Early diagnosis of myocardial infarction (MI) with cardiac troponin (cTn) assays at the point-of-care (POC) is suggested to shorten turn-around-time in the emergency department (ED). The present study aimed at comparing the diagnostic performance of two POC cTn assays with that of a central laboratory high-sensitivity (hs) method, under routine ED conditions. In 2,163 non-selected ED patients suspected for MI, the diagnostic performance of the POC troponin I (TnI), troponin T (TnT), and hs-TnT assay for the prediction of MI was evaluated based on receiver operating characteristic (ROC) analyses and compared with the performance based on the manufacturers' cut-offs. Due to an observed association between renal function as determined by estimated glomerular filtration rate (eGFR) and cTn concentrations, all analyses were stratified by renal function. In patients with normal renal function (eGFR > 60 mL/min/1.73m2), POC and hs assays showed a comparable diagnostic performance as quantified by the area under the ROC curve (AUC) of about 0.88. The ROC-derived optimal cut-off (OCO) levels for the different cTn assays clearly changed with decreasing kidney function. Impaired kidney function required OCO to be three to five times higher to achieve a comparable performance. Particularly cTnT concentrations were strongly associated with renal function. The three cTn assays demonstrated equivalent diagnostic performance in ED-patients admitted with suspected ACS in relation to the release diagnosis, supporting the use of POC testing in this setting. The present results implicate that application of eGFR-specific OCOs may decrease false-positives among patients with impaired renal function. Providing individual cut-offs depending on patients' eGFR might be an appropriate add-on tool to improve specificity in the diagnosis of MI.

Establishment of a reference interval for high-sensitivity cardiac troponin I in healthy adults from the Sichuan area

High-sensitivity cardiac troponin I (hs-cTnI) has been used in the diagnosis and risk stratification of acute myocardial infarction. However, there is no common consensus on an hs-cTnI reference interval for the Chinese population. The aim of this study was to describe the distribution of hs-TnI and establish the 99th percentile reference interval for hs-cTnI in healthy adults from the Sichuan area.Serum specimens were collected from 1485 healthy adults (731 men and 754 women ranging in age from 18 to 85 years) in Sichuan Provincial People's Hospital. All specimens were divided into 4 groups according to age distribution: 18 to 35 years, 36 to 50 years, 51 to 65 years, and ≥66 years. Specimens were further divided into younger/middle and older-aged groups based on a cut-off age of 50 years. The serum hs-cTnI concentration was determined using the Abbott ARCHITECT STAT hs-cTnI assay.The serum hs-cTnI concentration increased with age (P < 0.05). The 99th percentiles of hsTnI were 28.0 pg/mL among the whole population, 31.1 pg/mL among men, and 22.7 pg/mL among women. The age-dependent 99th percentiles of hs-cTnI in men and women were as follows: 28.8 versus 12.5 pg/mL for 18 to 35 years, 20.4 versus 9.2 pg/mL for 36 to 50 years, 24.2 versus 13.6 pg/mL for 51 to 65 years, and 27.9 versus 32.2 pg/mL for ≥66 years.The 99th percentile reference interval for hs-cTnI in healthy adults from the Sichuan area was similar to the manufacturer's recommendation. Men had a higher 99th percentile hs-cTnI value than women in the age range of 18 to 65 years.

Establishing reference intervals for galectin-3 concentrations in serum requires careful consideration of its biological determinants

BACKGROUND

Appropriately established reference intervals for laboratory biomarkers may help the interpretation of their results and facilitate clinical utilization.

OBJECTIVES

i) To determine reference intervals for serum galectin-3 measured using the Architect STAT immunoassay, and ii) to identify factors affecting galectin-3 concentrations.

METHODS

We recruited 533 questionnaire-identified apparently healthy individuals, in which laboratory biomarkers were used to detect asymptomatic myocardial injury and dysfunction, ongoing inflammation, hyperglycemia, dyslipidemia, and renal dysfunction. A final reference group of 180 subjects was selected.

RESULTS

2.5th and 97.5th percentiles of distribution of galectin-3 concentrations in the reference group (90% confidence interval) were 5.9 (5.0-6.8) and 18.1 (17.2-19.0) μg/L, respectively. Older age contributed to higher galectin-3 concentrations, but influenced derived reference intervals to a lesser extent. Other major determinants of galectin-3 concentrations observed in the questionnaire-screened population were not linked to galectin-3 in reference individuals. In aiming to decide if reference limits should be partitioned by age, we compared galectin-3 concentrations in subjects <40 (n=124) and ≥40years (n=56). Higher galectin-3 concentrations were found in older people (median, 12.4μg/L vs. 11.5μg/L, p=0.016). Accounting for manufacturer's declared imprecision at galectin-3 physiological concentrations of <10% (as CV) and the estimated URL for subjects ≥40 (18.8μg/L) and <40 (17.9μg/L), we recommend the adoption of a single URL for the overall adult population.

CONCLUSIONS

We established reference intervals for galectin-3 in which the effects of biological determinants were irrelevant. Although in healthy subjects age may affect galectin-3 release, this does not appear to necessitate age-related reference limits.

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.

High-sensitivity cardiac troponin testing in routine practice: economic and organizational advantages

Very seldom, if ever, a single laboratory test has provided such a paradigm shift in the managed care as cardiac troponin (cTn) testing. More than twenty years of improvements in test design and analytical features have contributed to revolutionize the clinical recommendations and guidelines, and the diagnosis of myocardial infarction (MI) is now highly dependent upon the kinetics of cTn within a suggestive clinical setting. Despite the advent of high-sensitivity cTn (HS-cTn) immunoassays has allowed a more accurate and timely diagnosis as well as a higher prognostic accuracy, the focus is now shifting on the most suitable algorithms and on a comprehensive approach to the clinical management of acute coronary syndrome (ACS). In this article we aim to discuss the implications of HS-cTn testing for ruling out and ruling in ACS. In the latter instance, main improvements are related to ACS diagnosis in women, in whom this pathology is still often underdiagnosed or misdiagnosed. A quick and accurate rule out will also regarded as a great advantage from both an organizational and economic standpoint. The advantages that will stem from this new approach have been recently assessed, and shortening of repeated testing 1 or 2 h from conventional algorithms entailing blood sampling at 3 and 6 h seems attainable. The larger benefits will definitely occur in clinical settings where the actual diagnosis rate of MI among patients with suspect ACS is lower and, consequently, the negative predictive value (NPV) of HS-cTn is the highest.

Determination of high-sensitivity cardiac troponin I 99th percentile upper reference limits in a healthy Korean population

OBJECTIVES

This study aimed to determine the 99th percentile upper reference limit (URL) concentration of cardiac troponin I (cTnI) with a high-sensitivity assay in a Korean population.

DESIGN AND METHODS

Cardio-healthy males and females were enrolled between March 2014 and March 2015. Participants with possible subclinical conditions were excluded on the basis of laboratory measures (primary: estimated glomerular filtration rate and glycated hemoglobin; secondary: B-type natriuretic peptide). Serum cTnI was measured using ARCHITECT STAT High-Sensitive Troponin-I Assay (Abbott Diagnostics, USA).

RESULTS

A total of 1204 participants completed a self-reporting questionnaire for inclusion in the study. Of these, we excluded 349 (29.0%) participants on the basis of primary (n=283) and secondary (n=66) laboratory measures. Ultimately, we included 854 participants (mean age, 49.8±10.2years) in the final analysis. The 99th percentiles of cTnI concentrations were 18 (90% confidence interval [CI], 14-35) ng/L for all participants, 20 (90% CI, 15-69) ng/L for males and 19 (90% CI, 11-41) ng/L for females. In both males and females, the median cTnI concentrations were significantly higher in participants aged 50years and older than in those younger than 50years old.

CONCLUSIONS

In this study, the reference population with Korean ethnicity had lower overall and male 99th percentile URLs than other reference populations. Our data suggest that 99th percentile URLs may be influenced by factors such as ethnicity, age distribution of participants, and selection criteria used to define a healthy reference population.