Cardiac troponin T immunoassay on biotin--streptavidin-coated microplates: preliminary performance in acute myocardial infarction

Sex-related differences in the prognostic utility of inflammatory and thrombotic cardiovascular risk markers in patients with chest pain of suspected coronary origin

Background

α1-antichymotrypsin (SERPINA3), high sensitivity C-reactive protein (hsCRP) and pentraxin 3 (PTX3) are acute phase proteins triggered by inflammation, whereas D-dimer, fibrin monomer and α2-antiplasmin are thrombo-fibrinolytic markers. Sex differences in relation to cardiovascular disease were investigated.

Methods

A total of 871 consecutive patients (61.0 % males; females: 77.3 years, males 69.1 years) were included. Of these, 380 were diagnosed with an acute myocardial infarction (MI). Stepwise Cox regression models, applying normalized continuous loge/SD values, were fitted for the biomarkers with all-cause mortality, MI and stroke, respectively, and a composite endpoint within 7 years as the dependent variables.

Results

Except for α2-antiplasmin, all biomarkers were significantly associated with all-cause mortality and the combined endpoint in the univariate analysis. None of the inflammatory biomarkers predicted all-cause mortality in females after multivariable adjustment but were significant predictors in males (SERPINA3: HR 1.34 (95 %CI 1.16-1.56), p < 0.0001. hsCRP: HR 1.19 (95 %CI 1.02-1.38), p = 0.027. PTX3: HR 1.22 [95 %CI 1.04-1.44], p = 0.018. The p-value for interaction suggests a sex difference in the prognostic weighting of SERPINA3 (p = 0.015). None of the thrombo-fibrinolytic biomarkers predicted all-cause mortality in males after adjustment, but D-dimer and fibrin monomer were significant predictors of all-cause mortality in females (HR 1.51 [1.29-1.78], p < 0.0001, and HR 1.28 [1.08-1.53] p = 0.005, respectively). A trend towards interaction for D-dimer (p = 0.07) may suggest a sex difference in its prognostic weighting.

Conclusion

SERPINA3, hsCRP and PTX3 predicted long-term all-cause mortality in males but not in females. The opposite relationship was observed for D-dimer and fibrin monomer.

α1-Antichymotrypsin Complex (SERPINA3) Is an Independent Predictor of All-Cause but Not Cardiovascular Mortality in Patients Hospitalized for Chest Pain of Suspected Coronary Origin

INTRODUCTION

SERPINA3 is an acute-phase protein triggered by inflammation. It is upregulated after an acute myocardial infarction (AMI). Data on its long-term prognostic value in MI patients are scarce. We aimed to assess the utility of SERPINA3 as a prognostic marker in patients hospitalized for chest pain of suspected coronary origin.

METHODS

A total of 871 consecutive patients, 386 diagnosed with AMI, were included. Stepwise Cox regression models, applying continuous loge-transformed values, were fitted for the biomarker with all-cause mortality and cardiac death within 2 years or all-cause mortality within the median 7 years as dependent variables. An analysis of MI and stroke, and combined endpoints, respectively, was added. The hazard ratio (HR) (95% CI) was assessed in a univariate and multivariable model.

RESULTS

Plasma samples from 847 patients were available. By 2-year follow-up, 138 (15.8%) patients had died, of which 86 were cardiac deaths. The univariate analysis showed a significant association between SERPINA3 and all-cause mortality (HR 1.41 [95% 1.19-1.68], p < 0.001) but not for cardiac death. Associations after adjustment were non-significant. By 7-year follow-up, 332 (38.1%) patients had died. SERPINA3 was independently associated with all-cause mortality from the third year onward. The HR was 1.14 (95% CI, 1.02-1.28), p = 0.022. Similar results applied to combined endpoints, but not for MI and stroke, respectively. The prognostic value of SERPINA3 was limited to non-AMI patients. No independent associations were noted among AMI patients.

CONCLUSIONS

SERPINA3 predicts long-term all-cause mortality but fails to predict outcome in AMI patients.

Borderline Values of Troponin-T and High Sensitivity C-Reactive Protein Did Not Predict 2-Year Mortality in TnT Positive Chest-Pain Patients, Whereas Brain Natriuretic Peptide Did

Background

Troponin-T (TnT), high-sensitive C-reactive protein (hsCRP), and Brain Natriuretic Peptide (BNP) have been shown to be independent prognostic indicators of total and cardiac death during short- and long-term follow-up.

Methods

We investigated prospectively the prognostic value of admission samples of TnT, hsCRP, and BNP in 871 chest-pain patients from South-Western Norway and 982 patients from Northern Argentina, based on a similar protocol and database setup. Follow-up was 2 years for the pooled population. The prognostic value of the selected biomarkers was investigated in quartiles of 239 patients with TnT values greater than 0.01 and up to and including 0.1 ng/mL, with continuous TnT as a potential confounder.

Results

After 24 months, 69 patients had died, of whom 38 died from cardiac causes. In the selected range of TnT, this biomarker was not significantly different between patients who died and survived (mean 0.0452 and 0.0457, p = 0.887). The BNP levels were significantly higher among patients dying than in long-term survivors [340 (142–656) versus 157 (58–367) pg/mL (median, 25 and 75% percentiles), p < 0.001]. In a multivariable Cox regression model for death within 2 years, the hazard ratio (HR) for BNP in the highest quartile (Q4) as compared to the lowest (Q1) was significantly related to total mortality [HR 2.84 (95% confidence interval (CI), 1.13–7.17)], p = 0.027, in addition to age (p ≤ 0.001) and hypercholesterolemia (p = 0.043). For cardiac death, the HR for BNP was 5.18 (95% CI, 1.06–25.3), p = 0.042. Several other variables (age, congestive heart failure, ST elevation myocardial infarction, and study country) were also significantly related to cardiac death. In a multivariable Cox regression model, hsCRP rendered no significant prognostic information for all-cause mortality (p = 0.089) or for cardiac mortality (p = 0.524).

Conclusion

In patients with borderline TnT values (greater than 0.01 and up to and including 0.1 ng/mL), this biomarker as well as hsCRP did not render prognostic information, whereas BNP was found to be a strong prognostic indicator of 2-year total and cardiac mortality.

Long-term prognostic value of CK-MB and the troponins after angioplasty in patients with stable angina

OBJECTIVES

The long-term prognostic value (> 5 years) of elevated cardiac biomarkers after elective coronary angioplasty is yet not clear. Most previous studies have included high risk, unstable patients and with conflicting results. The aim of this study was to determine the prognostic value of CK-MB mass vs. the cardiac troponins (values ≥ 3 times the reference) after elective angioplasty in low-risk patients with stable angina.

METHODS

A total of 202 consecutive patients were included in the final analysis. Patients with elevated values at baseline, and those suffering an acute coronary syndrome < 1 month before the time of inclusion, were excluded. Blood samples were drawn just before, 1-3 hours and 4-8 hours after the procedure and the next morning. Using a cutoff value of three times the reference, patients with high and low values (= controls) of CK-MB mass, cardiac troponin T (TnT) and troponin I (TnI) were compared. No patient developed new Q-waves on ECG. The median follow-up time was 82 months equalising 1600 patient years.

RESULTS

None of the patients died during the procedure or within the first 30 days after angioplasty, confirming a low risk cohort. There was an increasingly number of patients with levels ≥ 3 times the reference post procedure in TnT (10.4%) and TnI (16.8%) vs. CK-MB (6.9%). All cause mortality, readmission for acute coronary syndromes and target lesion revascularisation were more frequent in patients with high CK-MB, 42.9% vs. 22.3 %, p = 0.05 (log-rank test). Corresponding values for TnT were 33.3% vs. 22.7%, p = 0.22. In the TnI patients, there were more adverse events in controls vs. the high group, 25.0% vs. 17.6%, p = 0.34.

CONCLUSIONS

CK-MB mass values ≥ 3 times, contrary to the cardiac troponins, predicts worse long-term event-free survival after elective angioplasty in low-risk patients.

Long-term prognostic value of cardiac troponin I and T versus creatine kinase-MB mass after cardiac surgery in low-risk patients with stable symptoms

The long-term prognostic value of elevated cardiac biomarkers after elective cardiac surgery is not clear. The recent guidelines for diagnosing perioperative infarcts have advocated the use of similar thresholds for creatine kinase-MB (CK-MB) mass and the cardiac troponins. However, few previous data are available comparing these biomarkers after cardiac surgery, and it is not clear whether postoperative elevations of the troponins can be treated the same as elevations of CK-MB. We sought to compare the prognostic value of the cardiac troponins versus the CK-MB mass after elective cardiac surgery in low-risk patients with stable symptoms. A total of 204 consecutive patients undergoing cardiac surgery were included in the final analysis. Blood samples were drawn just before and 1 to 3 and 4 to 8 hours after the procedure, and every morning for 3 days thereafter. Patients with elevated baseline values were excluded. Using a cutoff value of 5 times the reference, patients with high and low values (controls) of CK-MB mass, cardiac troponin T (cTnT) and cardiac troponin I (cTnI) were compared. The median follow-up time was 92 months. None developed new Q-waves on the electrocardiogram. The incidence of the composite end point of all-cause mortality, readmission for acute coronary syndrome, and target vessel revascularization in the high CK-MB group was 41.2% compared to 21.8% in the controls (p = 0.004). The corresponding values for cTnT were 33.3% and 20.4% (p = 0.075) and for cTnI were 27.0% and 34.6% (p = 0.237). The p value in the isolated coronary artery bypass grafting subgroup (n = 156) was p = 0.043 for CK-MB, p = 0.137 for cTnT, and p = 0.795 for cTnI. High CK-MB (p = 0.001), ejection fraction (p = 0.002), and body mass index (p = 0.010) were the only variables independently related to reduced event-free survival. No such relation was found for high cTnT and cTnI. In conclusion, CK-MB was superior to the cardiac troponins (values > or =5 times the reference) in predicting long-term event-free survival after elective cardiac surgery in low-risk patients with stable symptoms undergoing coronary artery bypass grafting and/or valve surgery.

Holotranscobalamin and methylmalonic acid as prognostic markers following an acute myocardial infarction

OBJECTIVE

To evaluate whether low levels of holotranscobalamin (holoTC) or elevated levels of methylmalonic acid (MMA), both indicators of vitamin B(12) deficiency, might predispose to new cardiovascular events following an acute myocardial infarction (MI).

DESIGN

A prospective prognostic study.

SETTING

One hospital center in Stavanger, Norway.

SUBJECTS

A total of 300 patients admitted with an acute MI.

METHODS

Registration of new TnT positive coronary events (defined as TnT>0.05 microg/l and a typical MI pattern) and/or cardiac death during a median follow-up time of 45 months.

RESULTS

We compared the recurrence of events in the lowest quartile of holoTC (Q1<73.9 pmol/l) to the event rate above the 25% percentile (Q2-4). For methylmalonic acid (MMA) the same comparison was carried out for the upper quartile (Q4 > or =0.24 micromol/l) as compared with the event rate below the 75% percentile (Q1-3). After 18 and 45 months of follow-up, the odds ratio (OR) for Q1 vs Q2-4 for holoTC was 1.15 (95% confidence interval (CI) 0.91-1.46, P=0.25) and 1.05 (95% CI 0.86-1.29, P=0.64), respectively. For MMA the OR for Q4 vs Q1-3 was 0.95 (95% CI 0.76-1.19, P=0.67) after 18 months and 1.01 (95% CI 0.83-1.23, P=0.90) after 45 months.

CONCLUSION

This study showed no increased risk of future cardiovascular events associated with low levels of holoTC or high levels of MMA following an acute MI.

Temporal pattern of cardiac troponin I after thoracotomy and lung surgery

BACKGROUND

Several studies have shown that patients with perioperative myocardial infarction (MI) are at higher risk for subsequent cardiac events and the identification of these patients is important. However, the diagnosis of perioperative MI can be difficult in many cases. The cardiac troponins are biomarkers with high cardiospecificity, and the aim of this study was to assess cTnI and cTnT among other cardiac biomarkers after thoracotomy and lung surgery.

METHODS

24 consecutive patients were included in the final analysis. Venous blood samples were drawn prior to the procedure, 1-3, 4-6, 16-18 and 30-32 h after surgery. Thoracotomy was performed as a standard posterolateral incision on the left or right side under general anesthesia.

RESULTS

Both cTnI and cTnT were completely unaffected by the thoracotomy and the lung surgery. Furthermore, no single value of the troponins was above the 99th percentile at any time. In contrast, CK-MB was elevated in nearly half the patients, although the mean values complied well with the reference limit. CK and myoglobin were both considerably elevated and did not discriminate between acute myocardial infarction and release of the markers due to extracardiac injury.

CONCLUSIONS

Only the troponins were unaffected by extracardiac surgery and were, thus, reliable markers of myocardial injury in patients who underwent thoracotomy and lung surgery. If the troponins are unavailable, CK-MB mass combined with the CK-MB/CK percentage should be preferred.

Activated factor 12 (FXIIa) predicts recurrent coronary events after an acute myocardial infarction

BACKGROUND

Activated factor XII (FXIIa) is involved in vascular injury and repair, participating in inflammation, thrombosis, and fibrinolysis. We wanted to test the hypothesis that FXIIa may predict an acute coronary syndrome (ACS) after a myocardial infarction (MI) and to evaluate whether FXIIa is related to global markers of end-stage coagulation and inflammation, including fibrin monomer (FM) and ultrasensitive C-reactive protein (microCRP).

METHODS

In a prospective study of 300 patients with acute MI, we evaluated the predictive value of FXIIa in blood samples drawn 4 to 6 days after admission. Cardiac death, re-MI, and troponin-T-positive unstable angina pectoris were registered during a median follow-up period of 1.5 years.

RESULTS

In the upper quartile of FXIIa (Q4) (> or =2.23 ng/mL) 32.0% of patients had an ACS as compared with 16.9% of patients with FXIIa in the three lower quartiles (Q1-3, P =.008). Relative risk of recurrent ACS for patients with FXIIa in the Q4 as compared with Q1-3 was 1.89 (95% CI, 1.22 to 2.93). A secondary ACS occurred earlier in patients with FXIIa in the Q4 as compared with those with FXIIa in the Q1-3 (P =.0039). Conventional risk factors as potential confounders were not associated with time to event. FXIIa did not correlate with FM or microCRP, and the FM and microCRP levels were of a similar magnitude in the Q4 as compared with the Q1 and the Q1-3 of FXIIa.

CONCLUSIONS

FXIIa predicts recurrent coronary events after MI. The prognostic ability of FXIIa was not reflected by markers of hypercoagulability or inflammation.

Increased lipid peroxidation during long-term intervention with high doses of n-3 fatty acids (PUFAs) following an acute myocardial infarction

OBJECTIVE

To assess the oxidative burden of a highly concentrated compound of n-3 PUFAs as compared to corn oil by measuring thiobarbituric acid-malondialdehyde complex (TBA-MDA) by HPLC. We also studied the influence on TBA-MDA of statins combined with n-3 PUFAs or corn oil.

DESIGN

A prospective, randomised, double-blind, controlled study.

SETTING

One hospital centre in Stavanger, Norway.

SUBJECTS

A total of 300 subjects with an acute myocardial infarction (MI).

INTERVENTIONS

Gelatine capsules, containing 850-882 mg EPA and DHA as concentrated ethylesters, or 1 g of corn oil, were ingested in a dose of two capsules twice a day for at least 1 y. Alpha-tocopherol (4 mg) was added to all capsules to protect the PUFAs against oxidation.

RESULTS

After 1 y TBA-MDA increased modestly in the n-3 PUFA group (n=125), as compared to the corn oil group (n=130), P=0.027. Multiple linear regression analyses of fatty acids in serum total phospholipids (n=56) on TBA-MDA measured after 12 months intervention, showed no dependency. Performing best subsets regression, serum phospholipid concentration of arachidonic acid (20:4 n-6 PUFA) was identified as a predictor of TBA-MDA at 12 months follow-up, P=0.004. We found no impact of statins on TBA-MDA.

CONCLUSION

TBA-MDA increased modestly after long-term intervention with n-3 PUFAs compared to corn oil post-MI, suggesting biological changes induced by n-3 PUFAs, rather than simply reflecting their concentration differences. The peroxidative potential of n-3 PUFAs was not modified by statin treatment.

SPONSORSHIP

: Pharmacia A/S and Pronova A/S, Norway.

Percutaneous assessment of coronary blood flow and cardiac biomarkers

The aim of this study was to compare blood flow determined by coloured microspheres vs. Doppler intravascular ultrasound (US) combined with angiography. A second endpoint was to assess cardiac troponin I (cTnI) as a marker of myocardial injury. Doppler and microspheres were compared in 11 closed chest pigs. Blood flow was measured by catheter-based percutaneous technique in the left circumflex artery (LCx) and compared with coloured microspheres injected in the left ventricle. cTnI was measured in all pigs (73). The mean blood flow (mL/min-1) was 23.3 +/- 8.7 vs. 21.9 +/- 12.1 by Doppler vs. microspheres (p = 0.156), correlation coefficient r = 0.90, p = 0.006. The mean coronary flow with Doppler technique and microspheres in the middle LCx was 22.9 +/- 7.6 vs. 21.2 +/- 6.2 (p = 0.077), and distal 23.9 +/- 10.9 vs. 23.1 +/- 12.1 (p = 0.698). Coronary blood flow measured by Doppler and angiography was comparable to myocardial blood flow measured by coloured microspheres injected in the left atrium or the left ventricle. cTnI was more sensitive to ischaemia than CK-MB mass.

Laboratory diagnosis of patients with acute chest pain

The enzyme activities of creatine kinase (CK), its isoenzyme MB (CK-MB) and of lactate dehydrogenase isoenzyme 1 (LD-1) have been used for years in diagnosing patients with chest pain in order to differentiate patients with acute myocardial infarction (AMI) from non-AMI patients. These methods are easy to perform as automated analyses, but they are not specific for cardiac muscle damage. During the early 90's the situation changed. First creatine kinase MB mass (CK-MB mass) replaced the measurement of CK-MB activity. Subsequently cardiac-specific proteins troponin T (cTnT) and troponin I (cTnI) appeared on the scene, displacing LD-1 analysis. However, troponin concentrations in blood increase only from four to six hours after onset of chest pain. Therefore a rapid marker such as myoglobin, fatty acid binding protein or glycogen phosphorylase BB could be used in early diagnosis of AMI. On the other hand, CK-MB isoforms alone may also be useful in rapid diagnosis of cardiac muscle damage. Myoglobin, CK-MB mass, cTnT and cTnI are nowadays widely used in diagnosing patients with acute chest pain. Myoglobin is not cardiac-specific and therefore requires supplementation with some other analyses such as troponins to support the myoglobin value. Troponins are very highly cardiac-specific. Only the sera of some patients with severe renal failure, which requires hemodialysis, have elevated cTnT and/or cTnI without there being any evidence of cardiac damage. On the other hand, the latest studies have shown that elevated troponin levels in sera of hemodialysis patients point to an increased risk of future cardiac events in a similar manner to the elevated troponin values in sera of patients with unstable angina pectoris. In addition, the bedside tests for cTnT and cTnI alone or together with myoglobin and CK-MB mass can be used instead of quantitative analyses in the diagnosis of patients with chest pain. These rapid tests are easy to perform and they do not require expensive instrumentation. For routine clinical laboratory practice we suggest that in diagnosis of patients with chest pain, myoglobin and CK-MB mass measurements should be performed whenever they are requested (24 h/day) and cTnT or cTnI on admission to the hospital and then 4-6 and 12 hours later.

Cardiac troponins I and T in patients with suspected acute coronary syndrome: a comparative study in a routine setting

We compared cardiac troponin I (cTnI), using Access®, Sanofi Pasteur, and cardiac troponin T (cTnT), using Elecsys®, Boehringer Mannheim, in the first two routine blood samplings in a routine panel of cardiac markers for the biochemical diagnostic evaluation of patients with symptoms of acute myocardial infarction (AMI). No significant differences in the overall clinical performances of cTnI and cTnT were observed for the diagnosis of AMI (n = 68), but cTnI demonstrated lower initial sensitivity and higher specificity compared with cTnT. cTnT was increased to higher relative values than cTnI (P = 0.023). Discordances were found between cTnI and cTnT in sample I but not in sample II; positive cTnT/negative cTnI was more common than the opposite discordance (P = 0.027). cTnT was more frequently increased in patients with unstable angina pectoris (UAP) than cTnI (P = 0.038), with no significant differences between sample I and sample II; discordant results with respect to cTnI and cTnT appeared in 6 (33%) of these patients, all of which were positive for cTnT and negative for cTnI. Four patients with UAP (22%) developed AMI within 4 months; three were associated with increased cTnI and cTnT at the time of initial testing, and one was discordant (positive cTnT). In patients classified with no acute coronary syndrome (n = 84), five concordant positives for cTnI and cTnT were observed, indicating the existence of a myocardial injury of recent origin in these patients. AMI evolved in one of these patients 5 months later. We conclude that cTnT and cTnI detect acute myocardial injury with equal clinical performance in AMI patients classified by WHO criteria. cTnT was more frequently increased in patients with UAP than cTnI, but the clinical significance of this discordance could not be determined from this study.

Comparison of the troponin T and troponin I ELISA tests, as measured by microplate immunoassay techniques, in diagnosing acute myocardial infarction

We describe an improved procedure using a standard microplate immunoassay reader to measure the concentration of troponin T in human serum. We also describe an immunoassay for troponin I in serum. Only 160 microliters of serum are needed for a single analysis of each troponin. For comparison, creatine kinase MB mass analysis in serum was performed with a commercial luminometric method. From 95 apparently healthy people the following values were obtained: creatine kinase MB mass 2.6 +/- 1.2 micrograms/l, troponin T 0.027 +/- 0.025 microgram/l and troponin I 0.03 +/- 0.031 microgram/l. We compared the results of troponin T and troponin I methods with each other, as well as with those of creatine kinase MB mass measured in 48 patients with verified acute myocardial infarction and in 60 control patients with non-cardiac chest pain. The correlation between troponin T and troponin I values was 0.91 for the total material and 0.94 for 48 patients with acute myocardial infarction. Troponin I showed better earlier sensitivity than troponin T (p = 0.043). In nine patients in the control group, creatine kinase MB mass exceeded the reference limit of 5.0 micrograms/l, while in two patients the cut-off limit of 10.0 micrograms/l was also surpassed, pointing to non-specificity. In the group of infarct patients, the highest serum creatinine value was 193 mumol/l, whereas in the control group it was 406 mumol/l. The sera of patients with impaired renal function without any cardiac failure showed no increase in troponin T and troponin I values. In conclusion, serum creatine kinase MB mass and troponin I seem to confirm an acute myocardial infarction more rapidly than does troponin T; troponin I has the highest cardiac specificity.

Cardiac markers in the early hours of acute myocardial infarction: clinical performance of creatine kinase, creatine kinase MB isoenzyme (activity and mass concentration), creatine kinase MM and MB subform ratios, myoglobin and cardiac troponin T

We compared early markers of acute myocardial infarction (AMI) in the first 6 h from the onset of symptoms in 133 non-traumatized patients arriving at the emergency department with chest pain suggestive of AMI. Clinical performance parameters were calculated on the basis of 45 patients with AMI and 88 patients with a non-AMI diagnosis. At admission and in the first 0-3 h after the onset of chest pain the creatine kinase-MB (CK-MB) subform ratio was the most sensitive test at a comparable specificity level of 0.95. In the time interval of 3-5 h, myoglobin, the CK-MB mass concentration and the CK-MB subform ratio were associated with the greatest areas under receiver operating characteristic (ROC) curves, but differences between these tests were small and non-significant. At 6 h from the onset of pain, differences in clinical performance between the same three tests were even smaller whether or not samples drawn after the start of thrombolytic treatment were included in the test comparison. For confirmation of AMI at 6 h after onset of pain, CK-MB (activity and mass concentration) demonstrated the highest positive likelihood ratio, and for exclusion of AMI at 6 h the CK-MB subform ratio was associated with the highest negative likelihood ratio. However, differences between the CK-MB subform ratio, CK-MB mass concentration and myoglobin were not significant as estimated by the substantial overlap between the confidence intervals of the likelihood ratios and the ROC areas at 6 h. Cardiac troponin T (cTnT) demonstrated an ROC area equal to the CK-MB isoform ratio and myoglobin at 6 h. However, the likelihood ratio for ruling out AMI was lower, mostly due to the elevated cTnT in unstable coronary disease not defined as AMI. We conclude that the CK-MB subform ratio, CK-MB mass concentration and myoglobin do not demonstrate any significant differences in clinical performance for ruling in or ruling out acute myocardial infarction at 6 h after the onset of chest pain.