Half-Life and Clearance of Cardiac Troponin I and Troponin T in Humans.

BACKGROUND: Cardiac troponin (cTn) is key in diagnosing myocardial infarction (MI). After MI, the clinically observed half-life of cTn has been reported to be 7 to 20 hours, but this estimate reflects the combined elimination and simultaneous release of cTn from cardiomyocytes. More precise timing of myocardial injuries necessitates separation of these 2 components. We used a novel method for determination of isolated cTn elimination kinetics in humans. METHODS: Patients with MI were included within 24 hours after revascularization and underwent plasmapheresis to obtain plasma with a high cTn concentration. After at least 3 weeks, patients returned for an autologous plasma retransfusion followed by blood sampling for 8 hours. cTn was measured with 5 different high-sensitivity cTn assays. RESULTS: Of 25 included patients, 20 participants (mean age, 64.5 years; SD, 8.2 years; 4 women [20%]) received a retransfusion after a median of 5.8 weeks (interquartile range, 5.0-6.9 weeks) after MI. After retransfusion of a median of 620 mL (range, 180-679 mL) autologous plasma, the concentration of cTn in participants' blood increased 4 to 445 times above the upper reference level of the 5 high-sensitivity cTn assays. The median elimination half-life ranged from 134.1 minutes (95% CI, 117.8-168.0) for the Elecsys high-sensitivity cTnT assay to 239.7 minutes (95% CI, 153.7-295.1) for the Vitros high-sensitivity cTnI assay. The median clearance of cTnI ranged from 40.3 mL/min (95% CI, 32.0-44.9) to 52.7 mL/min (95% CI, 42.2-57.8). The clearance of cTnT was 77.0 mL/min (95% CI, 45.2-95.0). CONCLUSIONS: This novel method showed that the elimination half-life of cTnI and cTnT was 5 to 16 hours shorter than previously reported. This indicates a considerably longer duration of cardiomyocyte cTn release after MI than previously thought. Improved knowledge of timing of myocardial injury may call for changes in the management of MI and other disorders with myocardial injury.

Diagnostic utility of MR-proANP and NT-proBNP in elderly outpatients with a high risk of heart failure: the Copenhagen heart failure risk study.

Background: Amino-terminal-pro-B-type-natriuretic-peptide (NT-proBNP) is a diagnostic biomarker for heart failure (HF), but plasma concentrations are influenced by numerous factors. Mid-regional-pro-atrial-natriuretic-peptide (MR-proANP) have comparable diagnostic value in acute HF. However, data are lacking in the non-acute setting. This study sought to assess the diagnostic utility of MR-proANP in outpatients with a high risk of HF.Methods: This prospective study included 399 outpatients. Inclusion criteria were: age ≥ 60 years, ≥1 risk factor for HF (diabetes, chronic kidney disease, vascular disease, atrial fibrillation, hypertension), without known or suspected HF. Unrecognized HF was diagnosed based on clinical signs, patient-reported symptoms and echocardiography. Plasma concentrations of MR-proANP and NT-proBNP were analysed.Results: In total, 65 patients were diagnosed with HF or asymptomatic left ventricular systolic dysfunction (N = 12 LVEF ≤ 40%, N = 7 LVEF > 40% to ≤50%, N = 46 LVEF > 50%). Both MR-proANP (odds-ratio: 1.77; 95% CI:1.16-2.72; p = 0.009) and NT-proBNP (odds-ratio: 1.49; 95% CI:1.22-1.82; p < 0.001) were associated with HF. Area under receiver-operator characteristics curve (AUC) for the diagnosis of HF or asymptomatic left ventricular systolic dysfunction was higher for MR-proANP (AUC = 0.886; p < 0.001) and NT-proBNP (AUC = 0.910; p < 0.001) compared to patient-reported symptoms of HF (AUC = 0.830), but NT-proBNP added more diagnostic information compared to MR-proANP (p = 0.022).Conclusions: Both NT-proBNP and MR-proANP are useful biomarkers in the diagnosis of HF or asymptomatic left ventricular systolic dysfunction in a non-acute setting. However, NT-proBNP added more diagnostic information compared to MR-proANP.

Sex and Population-Specific 99th Percentiles of Troponin for Myocardial Infarction in the Danish Population (DANSPOT).

BACKGROUND: Sex- and population-specific 99th percentiles of high-sensitivity cardiac troponin (hs-cTn) are recommended in guidelines although the evidence for a clinical utility is sparse. The DANSPOT trial will investigate the clinical effect of sex- and population-specific 99th percentiles of cTn. We report the 99th percentiles derived from this trial and their dependency on kidney function. METHODS: We used samples from healthy Danish blood donors and measured hemoglobin A1c, N-terminal pro-brain natriuretic peptide and creatinine, and calculated an estimated glomerular filtration rate (eGFR). We compared 2 cutoffs for the eGFR of healthy participants (60 vs 90 mL/min/1.73 m2). The cTn assays investigated were Siemens Atellica and Dimension Vista hs-cTnI, Abbott hs-cTnI, and Roche hs-cTnT. RESULTS: A total of 2287 participants were sampled, of which 71 (3.1%) were excluded due to a history of heart disease (n = 4), insufficient material (n = 7), or a screening biomarker (n = 60). Of the remaining 2216 participants, 1325 (59.8%) had an eGFR ≥90 mL/min/1.73 m2. Compared to a cutoff of 60 mL/min/1.73 m2 for eGFR, using 90 mL/min/1.73 m2 resulted in lower 99th percentiles for females; Siemens Vista (46 vs 70 ng/L), Abbott (14 vs 18 ng/L), and Roche cTnT (10 vs 13 ng/L), and decreased the number of measurements above the manufacturers' 99th percentiles for all assays. CONCLUSIONS: We present reference values for 4 cTn assays for eGFR cutoffs of 60 and 90 mL/min/1.73 m2. These cutoffs differ based on the eGFR threshold for inclusion indicating that any chosen cutoff is also valuable with moderately reduced kidney function.

DANSPOT: A Multicenter Stepped-Wedge Cluster-Randomized Trial of the Reclassification of Acute Myocardial Infarction: Rationale and Study Design.

BACKGROUND: Cardiac troponins are the preferred biomarkers for the diagnosis of acute myocardial infarction. Although sex-specific 99th percentile thresholds of troponins are recommended in international guidelines, the clinical effect of their use is poorly investigated. The DANSPOT Study (The Danish Study of Sex- and Population-Specific 99th percentile upper reference limits of Troponin) aims to evaluate the clinical effect of a prospective implementation of population- and sex-specific diagnostic thresholds of troponins into clinical practice. METHODS: This study is a nationwide, multicenter, stepped-wedge cluster-randomized trial of the implementation of population- and sex-specific thresholds of troponins in 22 of 23 clinical centers in Denmark. We established sex-specific thresholds for 5 different troponin assays based on troponin levels in a healthy Danish reference population. Centers will sequentially cross over from current uniform manufacturer-derived thresholds to the new population- and sex-specific thresholds. The primary cohort is defined as patients with symptoms suggestive of acute coronary syndrome having at least 1 troponin measurement performed within 24 hours of arrival with a peak troponin value between the current uniform threshold and the new sex-specific female and male thresholds. The study will compare the occurrence of the primary outcome, defined as a composite of nonfatal myocardial infarction, unplanned revascularization, and all-cause mortality within 1 year, separately for men and women before and after the implementation of the new sex-specific thresholds. CONCLUSIONS: The DANSPOT Study is expected to show the clinical effects on diagnostics, treatment, and clinical outcomes in patients with myocardial infarction of implementing sex-specific diagnostic thresholds for troponin based on a national Danish reference population. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT05336435.

Evaluation of four laboratory-based high-throughput SARS-CoV-2 automated antigen tests compared to RT-PCR on nasal and oropharyngeal samples.

BACKGROUND: The demand for RT-PCR testing has been unprecedented during the SARS-CoV-2 pandemic. Fully automated antigen tests (AAT) are less cumbersome than RT-PCR, but data on performance compared to RT-PCR are scarce. METHODS: The study consists of two parts. A retrospective analytical part, comparing the performance of four different AAT on 100 negative and 204 RT-PCR positive deep oropharyngeal samples divided into four groups based on RT-PCR cycle of quantification levels. In the prospective clinical part, 206 individuals positive for and 199 individuals negative for SARS-CoV-2 were sampled from either the anterior nasal cavity (mid-turbinate) or by deep oropharyngeal swabs or both. The performance of AATs was compared to RT-PCR. RESULTS: The overall analytical sensitivity of the AATs differed significantly from 42% (95% CI 35-49) to 60% (95% CI 53-67) with 100% analytical specificity. Clinical sensitivity of the AATs differed significantly from 26% (95% CI 20-32) to 88% (95% CI 84-93) with significant higher sensitivity for mid-turbinate nasal swabs compared to deep oropharyngeal swabs. Clinical specificity varied from 97% to 100%. CONCLUSION: All AATs were highly specific for detection of SARS-CoV-2. Three of the four AATs were significantly more sensitive than the fourth AAT both in terms of analytical and clinical sensitivity. Anatomical test location significantly influenced the clinical sensitivity of AATs.

Sex differences of lipoprotein(a) levels and associated risk of morbidity and mortality by age: The Copenhagen General Population Study.

BACKGROUND AND AIMS: Lipoprotein(a) is a well-known causal risk factor for cardiovascular morbidity and mortality. Little is known about the effect of age and sex on lipoprotein(a) levels, and it is largely unknown if the same elevation in lipoprotein(a) confers the same increase in risk in women and men. We investigated whether lipoprotein(a) levels and lipoprotein(a) associated risks of morbidity and mortality by age are similar in women and men. METHODS: We included 37,545 women and 32,497 men from the Copenhagen General Population Study. RESULTS: Plasma lipoprotein(a) increased with age, and in women we found an additional increase around age 50 (age by sex interaction p = 8∙10-7). In women, levels were 27% higher after menopause (p = 4∙10-61) and 12% lower during hormone replacement therapy (p = 2∙10-19). Adjustment for estimated Glomerular Filtration Rate in both sexes and plasma estradiol in women resulted in attenuated sex differences in lipoprotein(a) levels. In sex and age stratified multivariable adjusted models, lipoprotein(a) >40 mg/dL(83 nmol/L) versus <10 mg/dL(18 nmol/L) was associated with increased risk of myocardial infarction, ischemic heart disease, aortic valve stenosis, and heart failure (men only), but not statistically significant with risk of ischemic stroke, cardiovascular mortality, or all-cause mortality. CONCLUSIONS: Lipoprotein(a) levels increased modestly around age 50 selectively in women; however, risk of morbidity and mortality for high lipoprotein(a) was similar in women and men above age 50. This implies that elevated lipoprotein(a) above age 50 is a relatively more common cardiovascular risk factor in women, pointing toward repeat measurements in women above age 50.

Equivalent Impact of Elevated Lipoprotein(a) and Familial Hypercholesterolemia in Patients With Atherosclerotic Cardiovascular Disease.

BACKGROUND: Genetically elevated plasma lipoprotein(a) and familial hypercholesterolemia each result in premature atherosclerotic cardiovascular disease (ASCVD); however, a direct comparison in the same population is needed of these 2 genetic traits on the risk of ASCVD. OBJECTIVES: We determined the level of plasma lipoprotein(a) that is equivalent to low-density lipoprotein (LDL) cholesterol in clinically and genetically diagnosed familial hypercholesterolemia on risk of myocardial infarction and ASCVD. METHODS: We examined the CGPS (Copenhagen General Population Study) with determination of lipoprotein(a) and familial hypercholesterolemia in 69,644 individuals followed for 42 years, during which time, 4,166 developed myocardial infarction and 11,464, ASCVD. RESULTS: For risk of myocardial infarction, the plasma lipoprotein(a) level equivalent to LDL cholesterol in clinical familial hypercholesterolemia was 67 mg/dL (142 nmol/L) for MEDPED (Make Early Diagnosis to Prevent Early Death), 110 mg/dL (236 nmol/L) for Simon Broome, 256 mg/dL (554 nmol/L) for possible DLCN (Dutch Lipid Clinic Network), and 402 mg/dL (873 nmol/L) for probable+definite DLCN, whereas it was 180 mg/dL (389 nmol/L) for genetic familial hypercholesterolemia. Corresponding values for ASCVD were 130 mg/dL (280 nmol/L), 150 mg/dL (323 nmol/L), 227 mg/dL (491 nmol/L), 391 mg/dL (849 nmol/L), and 175 mg/dL (378 nmol/L), respectively. Individuals with both elevated lipoprotein(a) and either familial hypercholesterolemia or a family history of premature myocardial infarction had a higher risk of myocardial infarction and ASCVD compared with individuals with only 1 of these genetic traits, with the highest HRs being for lipoprotein(a) upper 20% vs lower 50% of 14.0 (95% CI: 9.15-21.3) for myocardial infarction and 5.05 (95% CI: 3.41-7.48) for ASCVD. CONCLUSIONS: Lipoprotein(a) levels equivalent to LDL cholesterol in clinical and genetic familial hypercholesterolemia were 67 to 402 mg/dL and 180 mg/dL, respectively, for myocardial infarction and 130 to 391 mg/dL and 175 mg/dL, respectively, for ASCVD.

Lipoprotein(a) during COVID-19 hospitalization: Thrombosis, inflammation, and mortality.

BACKGROUND AND AIMS: High levels of lipoprotein(a) could worsen the outcome of COVID-19 due to prothrombotic and proinflammatory properties of lipoprotein(a). We tested the hypotheses that during COVID-19 hospitalization i) increased thrombotic activity and inflammation are associated with lipoprotein(a) levels, and ii) lipoprotein(a) levels are associated with rate of hospital death and discharge. METHODS: We studied 211 patients admitted to Copenhagen University Hospital in 2020 with COVID-19, that is, prior to any vaccination. Thrombotic activity was marked by elevated D-dimer while inflammation was marked by elevated interleukin-6, C-reactive protein, and procalcitonin. Patients were followed until death (N = 36) or discharge (N = 175). RESULTS: A 2-fold higher D-dimer was associated with 14% (95%CI: 8.1-20%) higher lipoprotein(a). Conversely, 2-fold higher interleukin-6, C-reactive protein, and procalcitonin were associated with respectively 4.3% (0.62-7.8%), 5.7% (0.15-5.2%), and 8.7% (5.2-12%) lower lipoprotein(a). For hospital death, the multivariable adjusted hazard ratio per 2-fold higher lipoprotein(a) was 1.26 (95%CI:0.91-1.73). Corresponding hazard ratios per 2-fold higher biomarker were 0.93 (0.75-1.16) for D-dimer, 1.42 (1.17-1.73) for interleukin-6, 1.44 (0.95-2.17) for C-reactive protein, and 1.44 (1.20-1.73) for procalcitonin. For hospital discharge, the multivariable adjusted hazard ratio per 2-fold higher lipoprotein(a) was 0.91 (95%CI:0.79-1.06). Corresponding hazard ratios per 2-fold higher biomarker were 0.86 (0.75-0.98) for D-dimer, 0.84 (0.76-0.92) for interleukin-6, 0.80 (0.71-0.90) for C-reactive protein, and 0.76 (0.67-0.88) for procalcitonin. CONCLUSIONS: In COVID-19 patients, thrombotic activity marked by elevated D-dimer was associated with higher lipoprotein(a) while elevated inflammatory biomarkers of interleukin-6, C-reactive protein, and procalcitonin were associated with lower lipoprotein(a); however, elevated lipoprotein(a) was not associated with rate of hospital death or discharge.

Prevalence of early stages of heart failure in an elderly risk population: the Copenhagen Heart Failure Risk Study.

Aims: To describe the prevalence of heart failure (HF) stages in elderly outpatients with risk factors for HF but without known HF, and characterise the clinical, biochemical and echocardiographic findings in each stage. Background: Early stages of HF are underdiagnosed; nevertheless, they are associated with an increased risk of hospitalisation and increased mortality. The prevalence of HF stages in elderly high-risk patients is unknown. Methods: A total of 400 patients were consecutively included: ≥60 years old, ≥1 risk factor for HF (diabetes, chronic kidney disease, cardiovascular disease, atrial fibrillation, hypertension), and without known or suspected HF. HF stages were defined as the following: stage A (risk factor for HF, normal echocardiography), stage B (abnormal echocardiography, without symptoms of HF) and stage C (abnormal echocardiography, symptoms of HF, clinical signs/increased plasma aminoterminal pro-B-type natriuretic peptide [NT-proBNP] concentrations). Results: After thorough examination 44.25% of patients were categorised as HF stage A, 37.5% were HF stage B and 18.25% HF stage C. Those with higher stages of HF were older (p<0.001) and more often had atrial fibrillation (p=0.006). The median plasma NT-proBNP concentrations (pg/mL) were 132.5 for HF stage A, 275.5 for HF stage B and 400.0 for HF stage C (p<0.001). Detectable plasma troponin-I was more frequent with abnormal echocardiography: HF stage A 9.7%, HF stage B 27.3% and HF stage C 30.1% (p<0.001). HF stage C reported higher score on the Minnesota Living with Heart Failure Questionnaire (p<0.001). Conclusions: In an elderly high-risk population without known or suspected HF, more than half were HF stage B or C. Higher stages of HF had increased plasma concentrations of NT-proBNP and troponin-I, besides a reduced quality of life. Focus on symptoms and signs of HF in this population are warranted.