Comparison of cardiac troponin T and troponin I assays--implications of analytical and biochemical differences on clinical performance

The usefulness of cardiac troponins for detection of myocardial cell necrosis and risk stratification has been established beyond doubt. Cardiac troponin testing is a key diagnostic element for the diagnosis and management of patients with acute coronary syndromes without ST segment elevation and is increasingly used in non-coronary diseases to indicate prognostically important cardiac damage. Given the biochemical and analytical differences of cTnT and cTnI there is ongoing controversy regarding the comparability and clinical performance of cTnT and cTnI. cTnT and cTnI are both expressed in cardiomyocytes but differ with respect to biochemical and analytical characteristics. While minor differences of analytical precision or biochemical properties are not relevant for diagnosis and management of patients with acute coronary syndromes and most diseases with non-coronary related elevations of cardiac troponins, these differences may be amplified in patients with chronic renal failure. In fact, recent studies in patients with end-stage renal disease under chronic hemodialysis have readdressed the issue whether cTnT and cTnI are really comparable. The present review will provide a state-of-the-art overview on the performance of cardiac troponins in acute coronary disease and other clinical conditions.     

Comparison of plasma cardiac troponins T and I in chronically hemodialyzed patients in relation to cardiac status and age.

Cardiac troponins (cTnT and cTnI) are useful tools for risk stratification in patients with unstable angina. However, their value in patients with renal failure has been questioned. In this study, we determined cTnT and cTnI at 3-month intervals during 9 months in 97 chronic renal failure (CRF) patients treated with hemodialysis. cTnT was measured using a third generation immunoassay and cTnI by fluorimetric immunoassay with a detection limit similar to that of cTnT (0.01 microg/l). In the renal patients without coronary heart disease (CHD(-) group), cTnT was more frequently elevated above cut-off for acute myocardial infarction (AMI) (up to 21.6%) than cTnI (no patient). In the absence of CHD, cTnT levels were positively correlated to age, and more than half of the CHD(-) patients aged over 60 years had cTnT levels above the upper reference limit (URL) of 0.04 microg/l (0.059+/-0.042 microg/l). cTnI increased with age in parallel to cTnT but mean levels did not exceed the URL of 0.08 microg/l in the CHD(-) patients aged over 60 years (0.036+/-0.031 microg/l). In the patients with documented cardiac events (CHD(+)) we found higher troponin levels than in the CHD(-) patients of the corresponding age, but for cTnl the differences between CHD(+) and CHD(-) patients were significant in the patients aged < or =60 years only (0.049+/-0.054 vs. 0.019+/-0.018 microg/l, p<0.05). For cTnT, the differences between patients with and without coronary events also tended to be less important in the eldest patients. There was a significant correlation between cTnI and cTnT levels in the CHD(-) and in the CHD(+) groups. Changes in the plasma levels of cardiac troponins are common in hemodialysis patients in the absence of CHD, and advanced age appears to amplify these changes. The reason could be that most hemodialysis patients with advanced age have subclinical lesions and demonstrate release characteristics of troponins that compare to those in patients with symptomatic coronary events. Therefore, it will be important to analyze troponin elevations above the URL or above the cut-off concentration for AMI in asymptomatic renal patients in relation to prognosis.     

Correlation of antemortem serum creatine kinase, creatine kinase-MB, troponin I, and troponin T with cardiac pathology

BACKGROUND: Spurious increases in serum troponins, especially troponin T, have been reported in patients with and without acute myocardial syndromes. METHODS: We studied 78 autopsied patients without clinical myocardial infarction (MI) and correlated histologic cardiac findings with antemortem serum creatine kinase (CK), its MB isoenzyme (CK-MB), cardiac troponin I (cTnI), and cardiac troponin T (cTnT). RESULTS: There was no significant myocardial pathology in 15 patients. Cardiac pathologies were in five groups: scarring from previous MI or patchy ventricular fibrosis (n = 9), recent MI (n = 27), healing MI (n = 7), degenerative myocyte changes consistent with congestive heart failure (CHF; n = 12), and other cardiac pathologies (n = 8). The median concentrations in the five groups were not significantly different for either CK or CK-MB. Compared with the no-pathology group, only the MI group was significantly different for cTnI, and the MI and other pathology groups were significantly different for cTnT. For patients with MI, 22%, 19%, 48%, and 65% had increased CK, CK-MB, cTnI, and cTnT, respectively; for CHF and other cardiac pathologies combined, the percentages were 28%, 17%, 22%, and 50%. For patients with increased cTnI, 72% and 28% had MI and other myocardial pathologies, respectively; patients with increased cTnT had 64% and 36%, respectively. Patients without myocardial pathology had no increases in CK-MB, cTnI, or cTnT. CONCLUSIONS: All patients with increased serum CK-MB, cTnI, and cTnT had significant cardiac histologic changes. The second-generation cTnT assay appears to be a more sensitive indicator of MI and other myocardial pathologies than the cTnI assay used in this study.     

心肌肌钙蛋白I、肌钙蛋白T、肌酸激酶同工酶MB早期诊断 急性心肌梗死敏感性及特异性比较分析

目的 探讨心肌肌钙蛋白Ⅰ（cTnI)、 肌钙蛋白T（cTnT)、 肌酸激酶同工酶MB（CK－MB）早期诊断急性心肌梗死的临床应用价值。方法 对60例急性心肌梗死（AMI）和40例不稳定型心绞痛（UA）患者的同一血样标本检测cTnI、cTnT、CK－MB3项指标,分别进行两组间比较,并对 AMI组和UA组各指标作对比分析。结果 cTnI、cTnT早期诊断急性心肌梗死灵敏度高于CK－MB,阳性率分别为63.3%、46.7%、18.3％,P＜0.01;cTnI和cTnT无显著差别,P＞0.05;cTnI、cTnT、CK－MB特异性相当。结论 心肌肌钙蛋白I和肌钙蛋白T对于AMI的早期诊断具有较高灵敏度和较强特异性,是心肌损伤特异笥标志物,cTnI检测方便、快捷、准确,具有较好的临床价值。     

肌钙蛋白I和T测定对急性心肌梗塞的诊断意义

目的探讨肌钙蛋白I（cTnI）和肌钙蛋白T（cTnT）测定对急性心肌梗塞（AMI）的诊断价值。方法对52例AMI患者采用免疫层析法进行检测cTnI和cTnT,以对照区和检测区均有显色带者为阳性,并作灵敏度和特异性的比较。结果以胸痛0～3h、4～6h两个时段观察其灵敏度,cTnI为56.7%和96.1%;cT-nT为50.0%和92.3%。特异性cTnI为100%和96.2%;cTnT为100%和91.6%。cTnI灵敏度高于cTnT,特异性cTnI与cTnT之间无显著性差异。结论对AMI急性胸痛患者可同时进行cTnI和cTnT检测,有利于AMI的诊断和治疗。     

血清心肌肌钙蛋白对心肌损伤的临床诊断价值

目的　探讨定量分析肌钙蛋白T(cTnT)、肌钙蛋白I(cTnI)对心肌损伤程度评价的临床意义。方法　对80例心肌梗死患[急性心肌梗死(AMI)50例、陈旧性心肌梗死(OMI)30例]、100例心脏手术患、60例非心脏手术患和20例健康人进行了血清cTnT、cTnI、肌酸激酶同工酶(CK—MB)和肌酸激酶(CK)检测。结果　(1)血清cTnT、cTnI、CK—MB和CK检测心肌损伤的敏感度和特异性分别为cTnT(72.4％，100.0％)、cTnI(81.8％，100.0％)，CK—MB(54.6％，87.5％)和CK(64.8％，62.2％)。(2)AMI和心脏手术组cTnT、cTnI、CK—MB和CK四项指标浓度均显高于正常对照组(P＜0.01)。(3)急性心肌梗死组、心脏手术组3h内cTnT和cTnI阳性检出率分别为(50％，56％)和(44％，45％)，明显高于CK—MB(24％，22％)和CK(20％，28％)；急性心肌梗死组、心脏手术组5d后cTnT和cTnI阳性检出率为(70％，66％)和(66％，61％)，而CK—MB仅为(4％，6％)，CK仅为(8％，10％)。结论　血清cTnT、cTnI能确切反映急性心肌梗死、心脏手术等心肌损伤程度，具有较宽的诊断窗口时间，是心肌损伤较敏感和特异的血清标志物。     

Diagnosis and risk stratification of patients with anginal pain and non-diagnostic electrocardiograms

Patients with acute chest pain suggestive of myocardial ischaemia, and normal or non-diagnostic electrocardiograms, form a difficult subgroup for diagnosis and early risk stratification. We prospectively evaluated the role of troponin T (cTnT), troponin I (cTnI), CKMB mass and myoglobin, in the diagnosis and risk stratification of 214 patients with acute chest pain of < or = 24 h and non-diagnostic or normal ECGs admitted directly to the Cardiac Unit of the Royal Victoria Hospital Belfast from the Mobile Coronary Care Unit or the Accident/Emergency Department. This was a single-centre prospective study, and follow-up (3 months) was complete for all patients. Blood was assessed for quantitative cTnT, cTnI, CKMB mass and myoglobin, and qualitative cTnT on admission and at 12 h. Diagnosis of index event and incidence of new cardiac events (death, non-fatal myocardial infarction, revascularization, or readmission for unstable angina) over 3 months were assessed. Based on standard criteria, myocardial infarction occurred in 37/214 (17%), and unstable angina in 72/214 (34%). At 12 h from admission, cardiac troponins had higher sensitivity for the diagnosis of acute coronary syndromes (myocardial infarction and unstable angina) than conventional markers (cTnI 48%, cTnT 38%, CKMB mass 30% or myoglobin 27%). At 3 months, a new cardiac event had occurred in 42/214 (20%). Significantly higher event rates occurred when any of the biochemical markers was elevated, but the statistical significance was highest for patients with elevated cTnI (p < 0.0001). Whilst gender, history of ischaemic heart disease (IHD), stress test response, cTnT, cTnI, CKMB mass and myoglobin were univariate predictors, cTnI at 12 h and stress test response were the only two independent significant predictors for a subsequent cardiac event at 3 months. Raised cTnI at 12 h after admission had the highest sensitivity for the diagnosis of acute coronary syndromes, and was independently associated with a 2-3 times increased risk of future cardiac events within 3 months among patients with acute chest pain suggestive of myocardial ischaemia but with normal or non-diagnostic ECGs.     

Cardiac troponin and beta-type myosin heavy chain concentrations in patients with polymyositis or dermatomyositis

Cardiac troponin T (cTnT), cardiac troponin I (cTnI), myosin heavy chains (MHC), myoglobin, creatine kinase (CK), and creatine kinase isoenzyme MB (CKMB), were measured in blood samples from 39 polymyositis (PM) or dermatomyositis (DM) patients without clinical evidence for cardiac involvement to evaluate their clinical usefulness in this patient population. MHC, myoglobin, and CKMB were frequently elevated and correlated with each other and with disease severity. Undetectable cTnI in all but one patient indicated that MHC was released from skeletal muscle, thereby providing the first laboratory evidence of frequent slow-twitch muscle fibre-necrosis in patients with PM or DM. CKMB was elevated in 51%, cTnT in 41%, and cTnI in only 2.5% of patients. cTnI did not correlate with other markers or with disease severity scores. The close correlations found between cTnT and skeletal muscle damage markers and the relationship between cTnT with disease severity without clinical evidence for myocardial damage suggest a release of cTnT from skeletal muscle. The relationship of cTnT with disease severity indicates a possible role of the marker for risk stratification. However, the prognostic values of cardiac troponins and other muscle damage markers in PM/DM patients remain to be compared in prospective outcome trials.     

Comparison of cardiac troponin T and I in healthy men and in aortic valve replacement.

Troponins are of outstanding importance for the diagnosis of myocardial infarction. Cardiac troponin T (cTnT) and the various cardiac troponin I (cTnI) assays differ with respect to method comparison, diagnostic sensitivity and diagnostic specificity. To understand the differences in the diagnostic behavior of troponin assays, AccuTnI and Elecsys Troponin STAT were used in a group of healthy men and in the follow-up of patients with aortic valve replacement (AVR). Within the healthy subjects AccuTnI was able to differentiate two subgroups from each other, whereas the cTnT concentrations of all subjects were below the detection limit. In AVR patients, cTnT and cTnI correlated sufficiently, if the postoperative periods were taken into consideration. There was a rapid increase in cTnI within 24 h. In contrast, a broad peak was evident for cTnT between 48 and 120 h. The results emphasize more the differences in the release of cTnI and cTnT from the cytoplasm and the thin filaments of the cardiomyocytes than the modifications of the troponins circulating in the blood.     

Lower cardiac troponin T and I results in heparin-plasma than in serum

BACKGROUND: The use of plasma rather than serum for determination of cardiac troponins can improve turnaround time and potentially avoid incomplete serum separation that may produce falsely increased results. We investigated the influence of incomplete serum separation and the effect of heparin-plasma on cardiac troponin concentrations. METHODS: Serum and heparin-plasma samples were drawn simultaneously from 100 patients (50 patients with acute coronary syndrome and 50 patients after open heart surgery) and measured on three different analytical systems, two for determination of cardiac troponin I (cTnI; Abbott AxSYM and Bayer ACS:Centaur) and one for cardiac troponin T (cTnT; Roche Elecsys cTnT STAT). Serum samples were reanalyzed after a second centrifugation to assess the influence of incomplete serum separation. RESULTS: Mean results (+/- 95% confidence interval) in heparin-plasma compared with serum were 101% +/- 2% (AxSYM cTnI), 94% +/- 3% (ACS:Centaur cTnI), and 99% +/- 3% (Elecsys cTnT). Differences >20% were seen in 11% of results on the ACS:Centaur, 9% of results on Elecsys cTnT, and 2% of results on the AxSYM. For the Elecsys cTnT assay, the magnitude of the difference between serum and plasma was independent of the absolute concentration and confined to individual samples, and was reversed by treatment with heparinase. A second centrifugation had no effect on serum results by any of the assays. CONCLUSION: The concentrations of troponins measured in heparin-plasma are markedly lower than in serum in some cases.     

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 troponin elevations in chronic renal failure: prevalence and clinical significance

OBJECTIVES: The aim of the study was investigate the prevalence of abnormal values of cardiac troponin T (cTnT) and cardiac troponin I (cTnI) in patients with chronic renal failure (CRF) and their clinical significance. DESIGN AND METHODS: We investigated the concentrations of cTnT and cTnI in 49 CRF patients without heart disease or diabetes. Cardiac TnT values were measured with a second generation immunoassay and cTnI with two immunoassays with different analytical sensitivity. All CRF patients underwent regular clinical follow-up over a 18-month period. RESULTS: No patients with CRF had elevated values of cTnI when measured with one assay and only 2 patients displayed minimally elevated values with the second assay. In contrast, 23 CRF patients (47%) displayed cTnT concentrations elevated above the upper reference limit. The elevated cTnT values observed were below the values detected in acute myocardial infarction and were not associated with adverse cardiac events during follow-up. CONCLUSIONS: Mildly elevated cTnT concentrations are common in patients with CRF and do not appear to be associated with adverse coronary events.     

Cardiac troponin T for prediction of short- and long-term morbidity and mortality after elective open heart surgery

BACKGROUND: Increased cardiac troponins in blood are observed after virtually every open heart surgery, indicating perioperative myocardial cell injury. We sought to determine the optimum time point for blood sampling and the respective cutoff value of cardiac troponin T (cTnT) for risk assessment in patients undergoing cardiac surgery. METHODS: In a series of 204 patients undergoing scheduled open heart surgery, mainly for coronary artery bypass grafting (n = 132) or valve repair (n = 27), cTnT concentrations were measured before and 4 and 8 h after cross-clamping and then daily for 7 days. Individual risk was assessed by use of the Cleveland Clinic Foundation Risk score and intraoperative risk indicators such as duration of cardiopulmonary bypass, cross-clamping, and perioperative release of cardiac markers. Patients were followed for 28 months. RESULTS: Cardiac mortality, all-cause mortality rates, and rates of nonfatal acute myocardial infarction (AMI) at 28 months were 6.9%, 8.8%, and 6.8%, respectively. cTnT was higher in patients with Q-wave AMI or postoperative heart failure requiring inotropic support, and in nonsurvivors. The ROC curve revealed a cTnT > or = 0.46 microg/L at 48 h as the optimum discriminator for long-term cardiac mortality. Stepwise logistic regression identified higher Cleveland Clinic Risk Score [odds ratio (OR) = 2.6 per point], cross-clamp time >65 min (OR = 6.6), and cTnT (OR = 4.9) as significant and independent predictors of long-term cardiac mortality. CONCLUSIONS: A single postoperative cTnT measurement can be used to estimate myocardial cell injury that impacts long-term survival after open heart surgery. It adds independently to established risk indicators.     

Single-point cardiac troponin T at coronary care unit discharge after myocardial infarction correlates with infarct size and ejection fraction

BACKGROUND: One of the major concerns in replacing creatine kinase MB (CK-MB) with cardiac troponins is the lack of evidence of the ability of troponins to estimate the size of acute myocardial infarction (AMI). We investigated the ability of a single measurement of cardiac troponin T (cTnT) at coronary care unit (CCU) discharge to estimate infarct size and assess left ventricular (LV) function in AMI patients. METHODS: We studied 65 AMI patients in whom infarct size was estimated by CK-MB peak concentrations and gated single-photon emission computed tomography (SPECT) myocardial perfusion using technetium-99m sestamibi and LV function by SPECT imaging. Measurements of cTnT and SPECT were performed 72 h (median) after admission (range, 40-160 h). SPECT was also repeated 3 months later. RESULTS: We found a significant correlation between cTnT and both the peak CK-MB concentrations (r = 0.76; P <0.001) and the perfusion defect size at SPECT (r = 0.62; P <0.001). cTnT was inversely related to LV ejection fraction (LVEF) assessed both early (r = -0.56; P <0.001) and 3 months after AMI (r = -0.70; P <0.001). cTnT >2.98 micro g/L predicted a LVEF <40% at 3 months with a sensitivity of 86.7%, specificity of 81.4%, and a likelihood ratio for a positive test of 4.7 (95% confidence interval, 4.0-5.4). CONCLUSIONS: A single cTnT measurement at CCU discharge after AMI is useful as a noninvasive estimate of infarct size and for the assessment of LV function in routine clinical setting.     

Improved assay of cardiac troponin I is more sensitive than other assays of necrosis markers

OBJECTIVE: Highly sensitive and specific assays of cardiac troponins I and T are the preferred biomarkers in diagnosing myocardial infarction (MI). Assays of cardiac troponin I (cTnI) have been improved with the addition of antibodies against the cTnI molecule and may have increased sensitivity. We hypothesized that a cTnI assay with modern antibody configuration will exhibit equal or better sensitivity in the setting of acute MI compared to cTnT and other markers of myocardial necrosis. MATERIAL AND METHODS: We investigated release kinetics of cTnI (Abbott ADV, Abbott Diagnostics), cTnT (Roche Diagnostics), CKMBmass, myoglobin and heart fatty acid binding protein (H-FABP) in 23 patients admitted with acute ST-segment elevation MI undergoing primary percutaneous coronary intervention. Calibrators for the Abbott ADV cTnI assay are traceable to the United States National Institute of Standards and Technology (NIST) reference material for cTnI. Eleven blood samples were drawn from each patient in the period from admission to 24 h. Biomarkers of necrosis showed marked increases in relative concentrations, especially within the first 2 h after admission. RESULTS: From 30 min after admission onwards, cTnI exhibited significantly higher relative concentrations compared to cTnT, CKMBmass, Myoglobin and H-FABP (p<0.05). CONCLUSIONS: The NIST standardized Abbott TnI ADV assay appears to be more sensitive than cTnT and other biomarkers in the early phase of MI.     

Cardiac troponins and renal function in nondialysis patients with chronic kidney disease

BACKGROUND: Serum cardiac troponin concentrations are commonly increased in end-stage renal disease (ESRD) in the absence of an acute coronary syndrome (ACS). The data on cardiac troponin I (cTnI) are more variable than those for cardiac troponin T (cTnT). There is little information on cardiac troponin concentrations in patients with chronic kidney disease (CKD) who have not commenced dialysis. METHODS: We studied 222 patients: 56 had stage 3 (moderate CKD); 70 stage 4 (severe CKD); and 96 stage 5 (kidney failure). Patients underwent echocardiography and were followed prospectively for a median of 19 months; all-cause mortality was recorded. RESULTS: Overall, serum cTnT was increased above the 99th percentile reference limit in 43% of all CKD patients studied, compared with 18% for cTnI. Serum cTnT and cTnI concentrations were more commonly increased in the presence of more severe CKD (11 and 6 patients in stage 3, 27 and 8 in stage 4, and 57 and 24 in stage 5 (P < 0.0001 and <0.02, respectively). Among 38 patients with detectable cTnI, 32 had detectable cTnT (r(s) = 0.67; P < 0.0001). There was evidence that decreasing estimated glomerular filtration rate increased the odds of having detectable cTnT (P < 0.001) but not cTnI (P = 0.128). There was no evidence to support an adjusted association of detectable cardiac troponins with increasing left ventricular mass index. Increased cTnT (P = 0.0097), but not cTnI, was associated with decreased survival. CONCLUSIONS: Increased cTnT and cTnI concentrations are relatively common in predialysis CKD patients, in the absence of an ACS, including among those with stage 3 disease. The presence of left ventricular hypertrophy alone does not explain these data. Detectable cTnT was a marker of decreased survival.     

肌钙蛋白Ⅰ与CK-MB联合检测对急性心肌梗死的诊断价值

目的探讨肌钙蛋白I(cTnI)与CK-MB联合检测对急性心肌梗死(AM I)的临床诊断价值。方法采用罗氏电发光2010自动生化分析仪和日立7180生化分析仪,测定62例AM I患者、50例健康体检者血清的cTnI、肌酸激酶(CK)和CK-MB,并对结果进行统计学分析。结果AM I组血清cTnI、CK和CK-MB高于正常对照组(P<0.01)。cTnI与CK-MB联合检测阳性率为96.7%,高于前三者,且动态检测对早期AM I敏感性更高、阳性持续时间更长。结论肌钙蛋白I与CK-MB联合检测能提高早期急性心肌梗死的检出率,具有更宽的诊断时间窗。     

Analytical and diagnostic performance of troponin assays in patients suspicious for acute coronary syndromes

BACKGROUND: The controversy whether there is a clinically significant difference between troponin T (cTnT) and troponin I (cTnI) in regard to predictive value and cardiac specificity is still ongoing. METHODS: We evaluated enzyme-linked immunosorbent assay systems for cTnI and cTnT in patients with acute coronary syndromes and multiple control groups to define threshold values for risk stratification and compare their predictive value. RESULTS: In 312 patients with noncardiac chest pain, cTnI levels were below the detection limit of 0.2 microg/L and cTnT levels were 0.011 [0.010-0. 013] microg/L. In patients with end-stage renal failure (n = 26) and acute (n = 38) or chronic (n = 16) skeletal muscle damage, median concentrations were 0.20 [0.20-0.35], below the detection limit, and 0.20 [0.20-0.25] for cTnI, and 0.04 [0.01-0.10], 0.011 [0.005-0.025], and 0.032 [0.009-0.054] microg/L for cTnT. In patients with acute coronary syndromes (n = 1130), maximized prognostic value for 30-day outcome (death, infarction) was observed at a threshold level of 1.0 microg/L for cTnI (29.0% positive) and at 0.06 microg/L for cTnT (35. 0% positive). Significant differences in the area-under-the-curve values were observed between cTnI and cTnT (0.685 vs. 0.802; p = 0. 005). For both markers, the area-under-the-curve values did not increase with the second (within 24 h after enrollment) or third (48 h) blood draw. CTnI showed a less strong association with 30-day outcome than cTnT. When cTnI was put in a logistic multiple-regression model first, cTnT did add significant information. CONCLUSION: By using the defined threshold values and the employed test systems, single testing for cTnI and cTnT within 12 h after symptom onset was appropriate for risk stratification. Despite the lower cardiac specificity for cTnT, it appears to have a stronger association with the patients' outcome, whereas, as previously shown, the ability to identify patients who benefit from treatment with a GP IIb/IIIa receptor antagonist is similar.     

心肌钙蛋白T定性在急性冠状动脉综合征诊断上的应用

目的　评价心肌钙蛋白T (cTnT)在急性冠状动脉综合征的诊断价值。方法　收入急诊ICU的急性冠状动脉综合征病人分为 :AMI组和UAP组 ,抽取肘部静脉血 1ml立即注入肝素抗凝试管中 ,混匀。用德国宝灵曼中国有限公司提供的肌钙蛋白T灵敏检测试纸条进行定性检查。同时用放免分析方法测定血清CK、CK MB及AST。结果　AMI组cTnT阳性率为 70 6 % ,UAP组阳性率 16 7% ,两组阳性率对比有显著性差异性 (P <0 0 1)。结论　cTnT是反映心肌细胞损伤的灵敏性、特异性均较好的生化指标 ,cTnT定性检测可用于ACS早期鉴别诊断 ,其临床意义优于血清CK、CK MB及AST。     

Risk stratification using serum concentrations of cardiac troponin T in patients with end-stage renal disease on chronic maintenance dialysis

BACKGROUND: It has been recently suggested that cardiac troponin T (cTnT) may be more sensitive than troponin I (cTnI) for subclinical myocardial cell injury in patients on chronic dialysis. METHODS: We prospectively compared the predictive value of cTnT with cTnI, atrial (ANP) and brain natriuretic peptide (BNP) in 100 consecutive outpatients on chronic dialysis without acute coronary syndromes over a period of 3 months, and assessed whether the combination of cTnT with clinical information including age, duration of dialysis, and medical histories was useful for risk stratification of these patients. During the 2-year follow-up period, 19 patients died, mostly due to cardiac causes (53%). RESULTS: The area under the receiver operator characteristic (ROC) curve for the cTnT as predictor of both overall and cardiac death was significantly greater than the area under the cTnI curve (p < 0.0001 and p = 0.01), the BNP curve (p < 0.001 and p < 0.01) or the ANP curve (p < 0.0001 and p < 0.005). In a stepwise multivariate Cox regression analysis, only cTnT (p < 0.05 and p < 0.01) and a history of heart failure requiring hospitalization (p < 0.05 and p < 0.005) were independent predictors of both all cause and cardiac mortality. Using parameters of cTnT > or =0.1 microg/l and/or history of heart failure, the overall and cardiac mortality rate for the low risk group (n=66) were 4.5% and 1.5%, respectively, 40% and 16% for the intermediate risk group (n=25), and 67% and 56% for the high risk group (n=9). CONCLUSION: cTnT concentrations offer a higher prognostic accuracy than cTnI, ANP and BNP in patients on chronic dialysis. The combination of elevated cTnT and a history of heart failure may be a highly effective means of risk stratification of these patients.