Early Diagnostic Efficiency of Cardiac Troponin I and Troponin T for Acute Myocardial Infarction

Objective : To compare the early diagnostic efficiency of the cardiac troponin I (cTn-I) level with that of the cardiac troponin T (cTn-T) level, as well as the creatine kinase (CK), CK-MB, and myoglobin levels, for acute myocardial infarction (AMI) in patients without an initially diagnostic ECG presenting to the ED within 24 hours of the onset of their symptoms. Methods : A prospective, observational, cohort study was performed involving chest pain patients admitted to a large urban community hospital. Participants were consecutive consenting ED chest pain patients ≥30 years of age. Exclusions included duration of symptoms >24 hours, inability to complete data collection, receipt of CPR, and ST-segment elevation on the initial ECG. Measurements included levels of cTn-I, cTn-T, CK, CK-MB, and myoglobin at the time of presentation and 1, 2, 6, and 12–24 hours after presentation as well as presenting ECG and clinical follow-up. Confirmation of the diagnosis of AMI was based on World Health Organization criteria. Results : Of the 177 patients included in the study, 27 (15%) were diagnosed as having AMIs. The sensitivities of all 5 biochemical markers for AMI were poor at the time of ED presentation (3.7–33.3%) but rose significantly over the study period. The sensitivity of cTn-T was significantly better than that of cTn-I over the initial 2 hours, but both markers' sensitivities were low (<60%) during this time frame. The cTn-I was significantly more specific for AMI than was the cTn-T, but not significantly better than CK-MB or myoglobin. Likelihood ratio analysis showed that the biochemical markers with the highest positive likelihood ratios for AMI during the first 2 hours following ED presentation were myoglobin and CK-MB. From 6 through 24 hours, the positive likelihood ratios for cTn-I, CK-MB, and myoglobin were superior to those of CK and cTn-T. Conclusions : cTn-I, CK-MB, and myoglobin are significantly more specific for AMI than are CK and cTn-T. Myoglobin is the biochemical marker having the highest combination of sensitivity, specificity, and negative predictive value for AMI within 2 hours of ED presentation. Neither cTn-I nor cTn-T offers significant advantages over myoglobin and CK-MB in the early (≤2 hours) initial screening for AMI. The cardiac troponins are of benefit in identifying AMI ≤6 hours after presentation.     

Evaluation of a New Assay for Cardiac Troponin I vs Creatine Kinase-MB for the Diagnosis of Acute Myocardial Infarction

Objective : To compare a new assay for cardiac troponin I (cTn-I) with an assay for creatine kinase-MB (CK-MB) for the diagnosis of acute myocardial infarction (AMI).
Methods : A prospective cross-sectional study of patients presenting with symptoms consistent with cardiac ischemia was performed at a university teaching hospital. Serum sampling for cTn-I and CK-MB was performed at 0, 1, 3, 8, and 16 hours after presentation. Normal values were defined as CK-MB ≤ 7 ng/mL and a relative index ≤ 2%, cTn-I ≤ 1.4 ng/mL. Final diagnosis was made using World Health Organization criteria, including standard enzyme sampling. Consecutive patients with AMI were compared with a randomly selected subset of patients without AMI to determine the sensitivity and specificity of the cTn-I and CK-MB assays for AMI, stratified by time from symptom onset. The ability of the biochemical cardiac markers obtained within 6 hours of symptom onset to predict later complications or need for interventions was assessed using odds ratios (ORs).
Results : Thirty-five patients who had AMI were compared with 136 patients who did not have AMI. The sensitivities and specificities of the cTn-I and CK-MB assays, stratified by time from symptom onset, were: Patients who had elevations in either CK-MB or cTn-I within 6 hours of symptom onset were at increased risk for cardiovascular complications and/or interventions (CK-MB, OR 5.8; cTn-I, OR 6.3).
Conclusion : cTn-I was as sensitive and specific for AMI as was CK-MB in ED patients who presented within 24 hours of symptom onset. However, cTn-I was more sensitive in patients who presented ≥ 24 hours after symptom onset. Elevations of either marker within 6 hours of symptom onset predict an increased risk of complications and/or need for interventions.     

乳酸评价急性胸痛的临床研究

目的　检验乳酸诊断急性心肌梗死(AMI)及判断危重心脏病患者预后的假说。方法　急性胸痛或其它典型AMI症状的患者检测静脉血乳酸。高于2.0mmol/L作为急性心脏疾病的预测值。同时检测心肌磷酸激酶(CK)和同工酶(CK-MB),记录ECG。结果　全部114例患者,65例乳酸高于2.0mmol/L。25例(22%)确诊为急性心肌梗死(AMI),其乳酸为2.7±0.7mmol/L。而Non～AMI乳酸为2.2±0.8mmol/L(P＜0.05)。乳酸诊断AMI的敏感性为96%(95%CI为89%～100%),特异性为55%(95%CI为45%～64%),乳酸阴性预计值为96%(95%CI为89%～100%)。胸痛患者乳酸升高的平均时间为发病3h以内。死亡或要求ICU治疗48h以上的患者其乳酸也明显升高,与不要求ICU治疗者比较其乳酸分别是5.0±4.3mmol/L比1.9±0.6mmol/L(P＜0.01)。结论　乳酸对AMI具有较高的阴性预计值,高乳酸血症与急性心脏病患者病死率及要求住院有明显的相关性。     

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.     

快速检测心肌脂肪酸结合蛋白诊断早期急性心肌梗死

目的 探讨快速检测血浆心肌脂肪酸结合蛋白（H-FABP）在诊断早期急性心肌梗死（AMI）中的价值.方法 比较H-FABP、cTnI、CK-MB和MYO四种物质定量检测诊断发病6 h内AMI的敏感性、特异性和准确性;比较H-FABP快速检测试剂条定性检测结果与ELISA定量检测结果.结果 H-FABP诊断发病3 h和6 h内AMI的敏感性显著高于cTnI和CK-MB,特异性相比,差异无显著性,诊断准确性显著高于cTnI、CK-MB和MYO.试剂条定性检测结果与ELISA比较符合率达96.9%.结论 H-FABP定性检测试剂条可用于早期AMI筛选诊断.     

缺血修饰性清蛋白的临床应用研究

目的探讨缺血修饰性清蛋白（IMA）在急性冠状动脉综合征（ACS）早期诊断价值。方法将89例ACS患者分别于胸痛发作2、4、6、12h及24h采血检测IMA、肌钙蛋白I（cTnI）和肌酸激酶MB同功酶（CK—MB）。其中急性心肌梗死41例,心绞痛48例。分析IMA对ACS的诊断价值。结果ACS患者IMA水平于胸痛发作2h明显增高,4h达到高峰,6h后降至正常。而cTnI,CK—MB在胸痛发作4h开始增高,6h明显增高,以后逐步递增至24h。在心绞痛、心肌梗死中,IMA水平升高以心绞痛最明显（P〈0．05）。结论IMA是诊断ACS早期敏感指标,是诊断心肌缺血的生化标志物。     

Human heart-type cytoplasmic fatty acid-binding protein (H-FABP) for the diagnosis of acute myocardial infarction. Clinical evaluation of H-FABP in comparison with myoglobin and creatine kinase isoenzyme MB.

Heart-type fatty acid-binding protein (H-FABP) is a low molecular weight cytoplasmic protein and present abundantly in the myocardium. When the myocardium is injured, as in the case of myocardial infarction, low molecular weight cytoplasmic proteins including H-FABP are released into the circulation and H-FABP is detectable in a blood sample. We have already developed a direct sandwich-ELISA for quantification of human H-FABP using two distinct types of monoclonal antibodies specific for human H-FABP. In this study we investigated the clinical validity of H-FABP as a biochemical diagnostic marker in the early phase of acute myocardial infarction (AMI). To evaluate the diagnostic usefulness of H-FABP in the early phase of AMI, blood samples were obtained from the following patients within 12 hours after the appearance of symptoms, and serum levels of H-FABP were compared with those of conventional diagnostic markers, such as myoglobin and creatine kinase isoenzyme MB (CK-MB). Blood samples were collected from patients with confirmed AMI (n=140), patients with chest pain who were afterwards not classified as AMI by normal CK-MB levels (non-AMI) (n=49) and normal healthy volunteers (n=75). The serum concentration of H-FABP was quantified with our direct sandwich-ELISA. The concentration of myoglobin mass was measured with a commercial RIA kit. The serum CK-MB activity was determined with an immuno-inhibition assay kit. The overall sensitivity of H-FABP, within 12 hours after the appearance of symptoms, was 92.9%, while it was 88.6% with myoglobin and 18.6% with CK-MB. The overall specificity of H-FABP was 67.3%, while it was 57.1% with myoglobin and 98.0% with CK-MB. The diagnostic efficacy rates with these markers were 86.2% (H-FABP), 80.4% (myoglobin) and 39.2% (CK-MB), respectively. The diagnostic validity of H-FABP was further assessed by receiver operating characteristic (ROC) curve analysis. The area under the curve (AUC) of H-FABP was 0.921, which was significantly greater than with myoglobin (AUC: 0.843) and CK-MB (AUC: 0.654). These parameters, such as sensitivity, specificity, diagnostic efficacy and diagnostic accuracy, obtained for patients with chest pain within 3 hours and/or 6 hours after the onset of symptoms were almost the same as those for patients within 12 hours after symptoms. H-FABP is more sensitive than both myoglobin and CK-MB, more specific than myoglobin for detecting AMI within 12 hours after the onset of symptoms, and shows the highest values for both diagnostic efficacy and ROC curve analysis. Thus, H-FABP has great potential as an excellent biochemical cardiac marker for the diagnosis of AMI in the early phase.     

心肌肌钙蛋白Ⅰ、肌红蛋白检测在急性心肌梗塞中的诊断价值

目的探讨CTnⅠ、Mb对急性心肌梗塞(AMI)早期诊断的价值.方法对26例AMI患者、41例不稳定性心绞痛(UAP)患者、30例骨骼肌损伤(SM)患者和30例健康者进行血清CTnⅠ、Mb、CK-MB的测定,并对AMI患者胸痛发生不同时段进行动态检测.结果 AMI患者入院时CTnⅠ、Mb、CK-MB的阳性检出率分别是65.4%、73.1%、53.8%.CK-MB在UAP组和SM组,Mb在SM组中有较高的阳性率,而CTnⅠ在UAP和SM组中未检出.CTnⅠ、Mb在AMI发生4h内就呈显著升高,三项指标的最高峰值在8～16h内均可出现,72h后Mb、CK-MB降至临界值,而CTnⅠ 7天后仍高于对照组.结论 CTnⅠ、CK-MB、Mb在AMI早期诊断价值基本相同,CTnI有更宽的诊断时间窗和独特的特异性,是AMI早期诊断的首选指标.     

Delta CK-MB outperforms delta troponin I at 2 hours during the ED rule out of acute myocardial infarction

It has been shown that a rise in creatine kinase MB bank (CK-MB) of > or = + 1.6 ng/mL in 2 hours is more sensitive and equally specific for detection of acute myocardial infarction (AMI) as compared with a 2-hour CK-MB > or = 6 ng/mL during the emergency department (ED) evaluation of chest pain. Because cardiac specific troponin I (cTnI) is thought to have similar early release kinetics as compared with CK-MB mass, we undertook a retrospective cohort study in 578 chest pain patients whose baseline CK-MB and cTnI was less than two times the hospital's upper limits of normal and who underwent a 2-hour CK-MB and cTnI to compare sensitivities and specificities of the 2-hour delta CK-MB (deltaCK-MB) and delta cTnI (delta cTnI) for AMI and 30-day Adverse Outcome (AO). Thirty day AO was defined as AMI, life-threatening complication, death, or percutaneous transluminal coronary angioplasty (PTCA)/coronary artery bypass graft (CABG) within 30 days of ED presentation. Optimum delta values were determined by choosing the smallest cutoff value greater than the assay precision where the deltaCK-MB and delta cTnI had a positive likelihood ratio for 30-day AO of > or = 15. A deltaCK-MB > or = +1.5 ng/mL was more sensitive than a deltaTnI > or = +0.2 ng/mL for AMI (87.7% versus 61.4%; P < .0005) and 30-day AO (56.7% versus 42.3%; P < .005). There were no differences in specificities for AMI and 30-day AO. Combining the two tests (MBdelta > or = +1.5 ng/mL and/or a deltaTnI > or = +0.2 ng/mL) resulted in an incremental increase in sensitivity of 89.5% for AMI and 61.9% for AO (P < .005). Patients with either a rise in CK-MB of > or = +1.5 ng/mL or rise in cTnI of > or = +0.2 ng/mL in 2 hours should receive consideration for aggressive antiischemic therapy and further diagnostic testing before making an exclusionary diagnosis of nonischemic chest pain.     

Cardiac markers protocols in a chest pain observation unit

The use of cardiac markers to identify high-risk patients in the observation unit is undeniable. As the literature reviewed here reveals, the history and ECG miss a significant portion of patients with acute cardiac ischemia. It appears that acute MI and some high-risk "unstable angina" observation unit patients can be identified within 6 hours of hospital presentation using a combination of cardiac markers. Testing these patients soon after symptom onset or on arrival in the ED for myoglobin, CK-MB subforms, or CK-MB delta appears to provide the best diagnostic usefulness. For testing later in the clinical course, CK-MB troponin I, or troponin T are of clear diagnostic and prognostic value. The markers currently used are unable to identify the significant subset of patients with "non-AMI" coronary syndromes, however. These patients require further testing with appropriate noninvasive or invasive diagnostic studies.     

Prospective evaluation of emergency department patients with potential coronary syndromes using initial absolute CK-MB vs. CK-MB relative index

We compared the predictive properties of an initial absolute creatine kinase-MB (CK-MB) to creatine kinase-MB relative index (CK-MB RI) for detecting acute myocardial infarction (AMI), acute coronary syndromes (ACS), and serious cardiac events (SCE). Consecutive patients > 24 years of age with chest pain who received an electrocardiogram (EKG) as part of their Emergency Department (ED) evaluation had CK and CK-MB drawn at presentation. Patients were followed prospectively during their hospital course. The main outcome was AMI, ACS or SCE (death, AMI, dysrhythmias, CHF, PTCA/stent, CABG) within 30 days. The sensitivity, specificity, PPV and NPV of CK-MB and CK-MB RI to predict AMI, ACS, and SCE were calculated with 95% CIs. We enrolled 2028 patients. There were 105 patients (5.2%) with AMI, 266 (13.1%) with ACS, and 150 with SCE (7.4%). Absolute CK-MB had a higher sensitivity than CK-MB RI for AMI (52.0 vs. 46.9, respectively), ACS (23.5 vs. 20.8, respectively), and SCE (39.6 vs. 36.0, respectively), but a lower specificity than CK-MB RI for AMI (93.2 vs. 96.1, respectively), ACS (93.1 vs. 96.1, respectively) and SCE (93.3 vs. 96.3, respectively); and lower PPV for AMI (35.7 vs. 46.5, respectively), ACS (42.0 vs. 53.4, respectively) and SCE (38.5 vs. 50.5, respectively). The negative predictive values were similar for all outcomes. We conclude that the risk stratification of ED chest pain patients by absolute CK-MB has higher sensitivity, similar NPV, but a lower specificity and PPV than CK-MB relative index for detection of AMI, ACS, and SCE. The optimal test depends upon the relative importance of the sensitivity or specificity for clinical decision-making in an individual patient.     

AMI患者早期CK同工酶亚型的高压电泳图谱分析

目的探讨CK同工酶亚型在AMI胸痛发作后24h内的变化规律,为AMI患者的早期诊断提供依据。方法采用REP全自动高压电泳仪检测AMI胸痛发作后不同时间以及对照组的CK-MM1、CK-MM2、CK-MM3、CK-MB1、CK-MB2等指标并进行荧光扫描,同时在Olympus2700全自动生化分析仪上测定CK、CK-MB的总活性,对所得数据进行恰当的统计分析。结果在AMI患者胸痛发作24h内,CK同工酶亚型有一特殊的变化规律:4~6h内,CK-MB2、CK-MM3开始升高,8~12h达高峰,92%的病人CK-MB2/CK-MB1>1.5,同时91%的病人CK-MM3/CK-MM1>0.5。结论CK同工酶亚型CK-MM3/CK-MM1、CK-MB2/CK-MB1的检测可作为AMI早期诊断的指标。     

缺血修饰清蛋白诊断急性冠脉综合征临床应用实验研究

目的评价缺血修饰清蛋白(IMA)对急性冠脉综合征(ACS)具有早期辅助诊断的意义。疾病类型不同其诊断意义亦不同。方法选择急性胸痛入院患者120例,其中急性心梗44例,心绞痛46例,非心源性胸痛30例。在胸痛发作5 h内采血做IMA实验,测定结果用ACB值(清蛋白钴结合能力,单位:U/ml)表示,观察IMA对各组疾病的诊断价值。另选30例急性心梗入院需溶栓治疗的患者,分别于溶栓前、溶栓开始后2,4,6,8,10,16,24 h采血做IMA实验,测定血清ACB值观察IMA对溶栓监测的意义。结果急性心梗组、心绞痛组患者血清IMA实验ACB值与正常对照组比较差异均有统计学意义(P<0.01),且心梗组患者血清IMA实验ACB值与心绞痛组比较差异有显著性(P<0.05)。在溶栓监测中各时间段的IMA实验ACB值比较差异无显著性(P>0.05)。结论IMA是诊断心肌缺血的早期指标,可用于ACS的早期诊断,且可明显提高对心绞痛早期诊断的灵敏性,但用于溶栓监测意义不大。     

The role of cardiac markers in the emergency department.

The emergency department (ED) evaluation of patients with potential acute coronary syndromes (ACS) has traditionally included initial cardiac marker testing for suspected acute myocardial infarction (AMI). While ED management decisions for patients with ACS have largely been based on history, physical examination, and a presenting 12-lead electrocardiogram (ECG), there is ample evidence that markers impact treatment decisions and provide risk stratification. Newer, more sensitive markers of myocardial necrosis have blurred the distinction between patients with and without classically defined AMI, and have focused attention on the continuum of ACS from angina to transmural Q-wave MI. Newer antiplatelet agents, the glycoprotein IIb/IIIa receptor blockers, are likely to receive increased ED utilization. This use will be partially driven by ED cardiac marker determination. Bedside, point-of-care testing is reliable technology that may shorten time to diagnosis and treatment of ACS in the emergency setting. The ED-based chest pain center (CPC) has become a popular tool to evaluate patients at low- to moderate-risk for ACS and a non-diagnostic ECG. Such centers use serial cardiac marker testing as a mainstay for evaluation and risk stratification. Cost issues have driven many diagnostic patient evaluations from the inpatient setting to such ED observation units. As this becomes more common for low- to moderate-risk patients with chest pain, serial assessment of cardiac markers, and their interpretation by emergency physicians, will become essential.     

心肌型脂肪酸结合蛋白对早期诊断心肌损伤的意义探讨

目的 探讨血清心肌型脂肪酸结合蛋白(H-FABP)在早期急性冠脉综合征(ACS)中的临床诊断价值.方法 应用全自动化学发光、生化分析仪检测46例ACS患者入院3～6h及6～12h两个时间段的血清中的H-FABP、肌钙蛋白I(cTnI)、肌红蛋白(MYO)、肌酸激酶同工酶(CK-MB).结果 H-FABP表现出了很好的检测早期(3～6 h)ACS的效果,比MYO、cTnI和CK-MB效果均要好(P＜0.05),单独检测的灵敏度达到了82.61％,而MYO、肌钙蛋白和CK-MB的诊断效果在6～12h段有明显提高.结论 H-FABP具有很好的早期诊断ACS价值,可以将H-FABP作为更早期诊断ACS的心肌损伤标志物应用于临床检测中.     

Emergency-department Diagnosis of Acute Myocardial Infarction and Ischemia: A Cost Analysis of Two Diagnostic Protocols

Objective:To assess the potential cost savings of the emergency-department (ED) diagnosis of acute myocardial infarction (AMI) and other myocardial ischemia using a nine-hour ED evaluation protocol.
Methods:This one-year study of chest-pain evaluation unit (CPEU) patient charges was undertaken at two midwestern urban university hospital EDs. Included in the study were 447 patients presenting to the EDs with chest pain consistent with myocardial ischemia, nondiagnostic electrocardiograms (ECGs), and stable vital signs. Following initial ED evaluation, CPEU patients underwent nine hours of continuous ECG ST-segment monitoring with serum CK-MB levels determined at zero, three, six, and nine hours. Nonrandomized concurrent chest pain patients with routine ED evaluation and hospital admission without CPEU workup served as controls. At Center 1, patients with negative CPEU evaluations underwent immediate echocardiography (echo) and graded exercise testing (GXT) followed by ED release (CPEU;REL). At Center 2, CPEU patients were released from the ED for outpatient stress thallium testing (CPEU; REL). At Center 2, CPEU patients with positive workups as indicated by elevated CK-MB levels, ischemia by ST-segment monitoring, or positive echo/GXT/stress thallium testing were admitted to the hospital for further testing. Control patients were admitted directly to the hospital to evaluate for AMI. Hospital charges for CPEU and control groups were compared.
Results:(Total charges in dollars, mean ± SD, Student's t-test):
Conclusion:At both centers, hospital charges related to the acute evaluation of chest pain were significantly lower with this ED diagnostic protocol for AMI and myocardial ischemia.     

Evaluation of a new automated system for the determination of ck-mb isoforms

We evaluated a new analyzer (Cardio REP) specifically designed for cardiac CK-MB isoenzyme and isoforms activity, with a performance time of 24 minutes. Ten AMI patients, with times elapsed between the onset of chest pain and admission to hospital ranging from 30 minutes to 4 hours, were monitored every 3–4 hours until the 16th hour of hospitalization. In each serum sample, in addition to total CK-MB and CK-MB isoforms measured by the Cardio REP analyzer, we also assayed total CK activity, CK-MB activity by immunoinhibition method, CK-MB mass concentration, CK-MB isoforms by REP method, troponin T, and myoglobin. The precision study demonstrated acceptable within assay and between assay CVs% for total CK-MB (8.1 and 10.4), MB₁ (9.1 and 14.2), and MB₂ (9.1 and 8.2) isoforms. The method was found to be linear up to 371 U/L for MB₂ isoform fraction and up to 516 U/L for total CK-MB. Results for CK-MB obtained with the Cardio REP correlated well with those for CK-MB activity obtained with the immunoinhibition method (r = 0.869) and those of CK-MB mass concentration (r = 0.923). The sensitivity of the Cardio REP CK isoforms method was found to be greater than that of the REP CK isoforms method. Time to first increased value of MB₂/MB₁ ratio and MB₂ isoform was earlier in comparison to that for CK-MB mass concentrations and similar to that for myoglobin, a marker that, however, lacks specificity. The diagnostic efficiency of CK-MB isoforms and the availability of a real-time, fully automated method for their measurement suggest the utilization of this biochemical marker in emergency for the early diagnosis of AMI.     

Diagnostic use of CK-MM and CK-MB isoforms for detecting myocardial infarction

Following acute myocardial infarction, total CK and CK-MB levels begin to rise 5 to 6 hours after the onset of chest pain. The serial profile of the rise and fall of both activities is nearly always indicative of AMI. The recent increase in the use of thrombolytic agents in an attempt to attain reperfusion of occluded coronary arteries alters the enzyme profiles observed in blood after AMI. After successful reperfusion a washout phenomenon occurs in which early restoration of blood flow to damaged myocardium causes an early rise in total CK and MB levels above the normal range 2 to 4 hours after AMI, with earlier and higher peak enzyme values. Recently reports have appeared describing numerous serum and plasma CK-MM and CK-MB isoform patterns after AMI. Following release from injured myocardium CK-MM3 and CK-MB2 (designated the tissue isoforms) are converted in the circulation to post-translation products (MM2, MM1, MB1, respectively). Studies have now shown that CK-MM isoform patterns provide a unique means of assessing the time of onset of necrosis and a monitor of the duration of enzyme release from the site of injury. Following AMI, MM3, the MM3/MM1 ratio, or both rises and peaks earlier than either total CK or CK-MB levels. During successful reperfusion, the rate of rise of CK-MM3 is more rapid and the MM3/MM1 ratio peaks earlier than without reperfusion. However, any concomitant release of CK-MM3 from skeletal muscle would decrease the clinical utility of MM isoforms in detecting myocardial damage. Recent advances in technology have shown that CK-MB2 rise parallels the CK-MM increase and also rises earlier than total CK and total MB levels and provides increased specificity for the myocardium. The full potential of the diagnostic utility of MM and MB isoforms will not be realized until a reliable, sensitive, simple, and rapid quantitative assay becomes available.     

Evaluation of a Bedside Whole-blood Rapid Troponin T Assay in the Emergency Department

Objective : To evaluate the performance of a new bedside whole-blood rapid assay for cardiac troponin T (cTnT) in patients presenting to the ED with symptoms consistent with acute coronary ischemia. Methods : A prospective, observational trial was performed in 8 participating medical centers. Serial blood samples were obtained on presentation to the ED and 3 and 6 hours later. The cTnT whole-blood rapid assays were performed immediately at the site. Treating physicians and patients were blinded to the results of the rapid assays. Serum samples were analyzed at the core laboratory for serum cTnT, creatine kinase (CK)-MB, and myoglobin. The sensitivity of the rapid assay for detecting acute myocardial infarction (AMI) was compared with the sensitivities of serum cTnT, CK-MB, and myoglobin assays. Results : Of 721 patients, 102 were diagnosed as having AMI. The median elapsed time from symptom onset to ED arrival was 3 hours. The sensitivities of the rapid assay for detecting AMI were 19.6%, 59.0%, and 69.7% at 0, 3, and 6 hours, respectively. The sensitivities of the serum cTnT assay (p-values for comparison with the rapid assay for cTnT) were 25.0% (p = 0.18), 69.6% (p = 0.04), and 79.8% (p = 0.02) at 0, 3, and 6 hours, respectively. The CK-MB and myoglobin sensitivities were 21.9%, 64.5%, and 81.0%; and 43.8%, 77.4%, and 71.4%, respectively. There were 7 patients with AMI who had negative rapid assay readings and positive serum cTnT levels; 4 of these patients were enrolled at the same site. Twenty patients not diagnosed as having AMI had at least one positive rapid assay. Fourteen of these 20 patients had a diagnosis of clinically relevant cardiac disease. Conclusions : The sensitivity of this whole-blood rapid cTnT assay for detecting AMI is comparable to that of current serum assays and offers the advantage of providing rapid bedside results. Discrepancies between serum and whole-blood assays for cTnT noted in this study may indicate the need for further education for the test reader prior to patient use.     

Value of troponin-T rapid assay, cardiac enzymes, electrocardiogram and history of chest pain in the initial diagnosis of myocardial infarction in the emergency department.

We conducted a prospective study of 152 adult patients presenting to an emergency department with chest pain or symptoms suggestive of acute myocardial infarction (AMI) to evaluate the first electrocardiogram (ECG), creatine kinase (CK)-MB and Troponin-T Rapid Assay (TnT) alone or in combination with chest pain in the initial diagnosis of AMI. A provisional diagnosis was made after the history, physical examination and the first ECG reading. Blood specimens were taken for TnT, CK and CK-MB mass. A final discharge diagnosis of AMI was made according to World Health Organization criteria. Seventy-six (50%) of patients had a final diagnosis of AMI. The sensitivities of the first ECG, first CK-MB mass and first TnT were 76.3% (95% confidence interval (CI), 66.8-85.9), 38.2% (95% CI, 27.2-49.1) and 31.6% (95% CI, 21.2-42.0) respectively. The area under the curve for a combination of ECG, CK-MB mass, TnT and chest pain was the highest at 0.937 when compared with chest pain with varying combinations of tests. A combination of the first ECG, CK-MB mass and TnT had a negative predictive value (NPV) of 87.9% (95% CI, 80.0-95.8). The first ECG was the most sensitive test while the combination of chest pain, ECG, cardiac enzymes and TnT gave the best results in the initial diagnosis of AMI. If the first ECG, CK-MB mass and TnT are all negative, the probability of having an AMI is 12%.