Aptamer-Based Gold Nanoparticle Lateral Flow Assay for Rapid Detection of Cardiac Troponin I

MAJOR perioperative cardiac events in patients undergoing noncardiac surgery continue to be a significant source of perioperative morbidity with ranges from 1.4% in relatively unselected patients1to 6% in patients older than 70 yr with cardiac disease.2Moreover, perioperative myocardial infarction (PMI) is one of the most important predictors of short- and long-term morbidity and mortality associated with noncardiac surgery.3–6The actual rate of PMI varies between studies in part because of the definition used and the method of surveillance. Part of the definition depends on the biomarkers (e.g. , creatine kinase [CK], lactate dehydrogenase, and troponin) used to define PMI. This article will review the evolution in the use of biomarkers and how more specific biomarkers have increased the rate of PMI detected.7According to the traditional definition, at least two of the three criteria must be fulfilled to diagnose myocardial infarction (MI): (i) typical ischemic chest pain; (ii) increased serum concentration of CK-MB (myocardial band) isoenzyme; and (iii) typical electrocardiographic findings, including development of pathologic Q waves. The advent of sensitive and specific serologic biomarkers has resulted in a major shift in the classic paradigms for diagnosing infarction.Devereaux et al. 8suggest that only 14% of patients experiencing a PMI will have chest pain and only 53% will have a clinical sign or symptom that may trigger a physician to consider an MI. The large proportion of clinically unrecognized MIs can be explained by several factors present in the immediate postoperative period: analgesics, intubation and sedation, and a host of more common explanations for potential signs and symptoms, such as atelectasis, pneumonia, hypovolemia, and bleeding.Electrocardiography plays a key role in the diagnostic workup of suspected MI. The changes in the ST-T waveforms and the Q waves potentially allow the clinician to date the event, to suggest the infarct-related artery, and to estimate the amount of myocardium at risk. Electrocardiography criteria for diagnosis of acute MI in the absence of left ventricular hypertrophy and left bundle branch block are ST elevation MI—new ST elevation at the J-point in two contiguous leads with the cutoff points: more than or equal to 0.2 mV in men or more than or equal to 0.15 mV in women in leads V2–V3and/or more than or equal to 0.1 mV in other leads; non-ST elevation MI (ST depression and T-wave changes)—new horizontal or down-sloping ST depression more than or equal to 0.05 mV in two contiguous leads; and/or T inversion more than or equal to 0.1 mV in two contiguous leads with prominent R wave or R/S ratio more than 1.However, the electrocardiogram by itself is often insufficient to diagnose acute myocardial ischemia or infarction because ST deviation may be observed in other conditions such as acute pericarditis, left ventricular hypertrophy, left bundle branch block, Brugada syndrome, and early repolarization patterns. Furthermore, in cardiomyopathy, for example, Q waves may occur due to myocardial fibrosis.9A more complete review can be found elsewhere.10Measurement of cardiac markers in blood has been the mainstay for diagnosis of acute MI for nearly 50 yr.A loss of cellular integrity of the sarcolemma results in the release of a number of proteins into the circulation that can be used as biochemical markers of acute myocardial necrosis. CK, SGOT (more recently known as AST), lactate dehydrogenase, myoglobin, and troponins are some of these markers. The timing of their appearance and disappearance in blood is mainly dependent on quantity of release, molecular size, and solubility (fig. 1). The first practical test used for biochemical detection of myocardial damage was the measurement of transaminases described in 1954.11Having wide tissue distribution, AST and lactate dehydrogenase are less specific for myocardial necrosis and offer no advantage over CK isoenzymes. Myoglobin, a heme-related protein abundant in cardiac and skeletal muscle, is an early marker of myocardial necrosis. It is detectable in the plasma 1–2 h after the onset of chest pain, with a peak at 3–8 h. With the availability of assays for CK isoenzymes, these tests were gradually abandoned, at least for an early diagnosis of MI.CK is the enzyme responsible for catalyzing the transfer of high-energy phosphate from creatine phosphate to adenosine triphosphate. CK is known to rise within 4–8 h after an acute MI and to decline to normal levels within 3–4 days. In 1960, Dreyfus et al. 12demonstrated markedly increased plasma CK activity in patients with MI. Total CK found in the normal circulation varies tremendously, and CK is a well-recognized marker of rhabdomyolysis. The problem of multiple etiologies makes interpretation of CK release more difficult in the surgical population.In 1966, van der Veen and Willebrands13demonstrated that CK-MB is a highly specific marker of MI. In the 1970s, it became evident that CK-MB was to be the standard for the diagnostic and quantitative assessment of MI. CK isoenzyme analysis substantially increased the sensitivity of this test for the diagnosis of acute MI. However, other types of myocardial injury, such as myocarditis, trauma, and cardiac surgery, also cause the release of CK-MB.14A variety of techniques were developed to further improve the sensitivity and rapidity of assaying for CK-MB. In the mid-1980s, the development of an antibody specific for CK-MB15marked the beginning of the era of immunologic detection of biomarkers. This technique of mass assay offered the advantage of measuring protein concentration over enzymatic activity. With direct analysis of CK-MB irrespective of total activity, it was quickly recognized that the myocardium is not the only tissue containing large amounts of CK-MB as initially believed.16CK-MB has been found in the small intestine, tongue, diaphragm, uterus, and prostate. Skeletal muscles also contain CK-MB in small amounts. In the surgical setting, the use of the CK-MB fraction is complicated by increased levels of both total CK and noncardiac CK-MB.The shift from transaminases and dehydrogenases to isoenzymes of the latter and then to CK, CK-MB, and CK-MB mass improved test precision, resulting in greater sensitivity and specificity in the diagnosis of MI over time and better case classifications. However, these tests still did not allow the definite distinction of skeletal and cardiac muscle injuries. This lack of cardiospecificity accelerated the desire for a more specific test than CK-MB.CK-MB was considered the benchmark for MI diagnosis from the 1980s through the late 1990s. The diagnostic sensitivity of both CK-MB (activity or mass) and the troponins markedly increases with time. Sampling to at least 10 h yields approximately 90% diagnostic sensitivity with either biomarker.17In a meta-analysis by Balk et al. ,18CK-MB showed a rather low cumulative sensitivity of 79% and a cumulative specificity of 96% in emergency department patients. It could be argued, however, that inclusion of studies that mixed results of assays, different cutoff strategies, and less than ideal sampling almost certainly led to underestimation of diagnostic sensitivity. Wu and Lane19limited inclusion to studies that used CK-MB mass assays in samples collected over the appropriate timeframe of 12–24 h after the onset of symptoms. Their meta-analysis reported a cumulative sensitivity of 97% and cumulative specificity of 90%.The cardiac troponins are regulatory proteins with both cytosolic and structural pools that are released because of necrosis. The troponin complex is located on the thin filament of striated muscle and consists of three subunits: troponin T, a binding protein that attaches the troponin complex to tropomyosin; troponin I, which modulates the interaction of actin and myosin by acting as an inhibitor of actomyosin adenosine triphosphatase activity; and troponin C, the calcium-binding subunit of the troponin complex. The cardiac forms are designated cardiac troponin I (cTnI) and cardiac troponin T (cTnT). Cardiac troponin has nearly absolute myocardial tissue specificity and high clinical sensitivity.20Several large studies of patients with acute coronary syndrome support the clinical efficacy of troponin over the previous gold standard: the CK and its MB fraction.Although there is only one assay for cTnT, there is a multiplicity of assays for cTnI with substantial heterogeneity of assay sensitivities.21Manufacturers are now developing a new generation of high-sensitivity cTn assays that are more precise at low concentrations and measure cTn concentration at less than 1 ng/l. Of note, cTn assays are neither standardized nor harmonized. Different assays are composed of different antibody configurations recognizing different epitopes of cTnI, suggesting that specific assays may detect slightly different groups of patients, depending on the nature and timing of cTn release.22The performance of assays and the release kinetics and plasma clearance of both troponin T and I have been described elsewhere.23–25An increased value for cardiac troponin is defined as a measurement exceeding the 99th percentile of a normal reference population (upper reference limit). Detection of a rise and/or fall of troponin is essential to the diagnosis of acute MI. Blood samples for measurement of troponin should be drawn on first assessment and 6–9 h later. The above-mentioned discriminatory percentile is designated as the decision level for the diagnosis of MI and must be determined for each specific assay with appropriate quality control. It has also been recommended that optimal test reproducibility should be defined as less than or equal to 10% imprecision at the 99th percentile upper reference limit for each assay.One of the biggest issues apart from the problem of selecting relevant reference subjects is the current practice of the Food and Drug Administration of approving assays based on higher receiver-operating characteristic-optimized cutoffs. In a recent issue of clinical chemistry, Apple26introduced his concept of a scorecard approach to decide which assays are acceptable for use in clinical practice. He proposed a two-tier system using both the 99th percentiles and imprecision values at the 99th percentile based on a young, healthy reference population that is diversified by sex, race, and ethnicity.The first major study to evaluate the perioperative use of cTnI was conducted by Adams et al. 27The authors compared electrocardiogram, total CK, CK-MB, and cTnI with the gold standard (new akinesia or dyskinesia on postoperative transthoracic echocardiography) for detection of perioperative infarction in 108 patients undergoing vascular or spine surgery. Blood samples were obtained every 6 h for a least the first 36 h after surgery. In this population, a PMI as defined by new abnormalities of wall motion was diagnosed in 8 patients (8%). The sensitivity of cTnI was 100% and that of CK-MB was 75%. The difference between the specificity of cTnI (99%) and that of CK-MB (81%) was significant (P < 0.005). Thus, these data did not establish the superior sensitivity of cTnI compared with CK-MB, only its superior specificity for the detection of perioperative infarction.Lee et al. 28evaluated the diagnostic performance of cTnT as a marker for myocardial injury in 1,175 patients aged 50 yr or older and undergoing major noncardiac surgery. CK-MB and electrocardiographic criteria were used to define acute MI. cTnT was measured in the recovery room after surgery and on the next two postoperative mornings. Acute MI was diagnosed in 17 patients (1.4%). cTnT increases occurred in 87% of patients with MI and in 16% of patients without MI, yielding a sensitivity of 87% and a specificity of 84%. The receiver-operating characteristic curves indicated that the two tests had similar diagnostic performance in detecting MI but that cTnT was superior for prediction of complications.Metzler et al. 29conducted a study with the aim of examining the perioperative pattern of changes in troponin. Blood sampling was performed daily from the day before surgery until the fifth postoperative day (POD) in 67 patients with cardiac risk undergoing elective noncardiac surgery. Eight of the 13 patients (12%) with increased cTnT concentrations had an adverse outcome. In seven patients, CK-MB and troponin increases were discordant. With a cTnT cutoff at 0.2 ng/ml, the positive and negative predictive values for adverse outcome were only 62% and 100%, respectively. By choosing a higher cutoff of 0.6 ng/ml, the positive and negative predictive values for adverse outcome were 88% and 98%.Haggart et al. 30compared the value of cTnI and CK/CK-MB ratios for detection of myocardial injury in 59 patients undergoing either emergency (24) or elective aortic surgery. More than half the patients undergoing emergency surgery and more than a quarter of those having elective surgery suffered myocardial necrosis as determined by detectable cTnI levels. This was accompanied by an increased CK-MB/CK ratio in less than one-fifth of patients.The use of cTnI in diagnosing PMI in the setting of orthopedic surgery was evaluated by Jules-Elysee et al. 31in 85 patients with risk factors for coronary artery disease. In this population, cTnI seemed to be as sensitive as and more specific than the CK-MB index.Martinez et al. 32evaluated surveillance strategies for the diagnosis of PMI using TnI in a cohort of 467 patients at high risk who required noncardiac surgery, with the goal of identifying the highest diagnostic yield. The diagnosis of myocardial injury was determined by biomarkers combined with either postoperative changes on 12-lead electrocardiogram or one of three clinical symptoms consistent with MI (chest pain, dyspnea, or requirement for hemodynamic support). The incidence of MI was 9.0% by the criterion of cTnI greater than or equal to 2.6 ng/ml, 19% by TnI greater than or equal to 1.5 ng/ml, 13% by CK-MB mass, and 2.8% by CK-MB ratio. The specificity of TnI greater than or equal to 2.6 ng/ml as an indicator of MI was 98%, and its positive predictive value was 85%. Using this cutoff, the strategy with the highest diagnostic yield was surveillance on PODs 1, 2, and 3.Le Manach et al. 33used cTnI surveillance after abdominal aortic surgery in 1,136 patients to better evaluate the incidence and timing of PMI (TnI ≥ 1.5 ng/ml) or myocardial damage (abnormal cTnI < 1.5 ng/ml). Abnormal cTnI concentrations were noted in 163 patients (14%), of whom 106 (9%) had myocardial damage and 57 (5%) had PMI. In 34 patients (3%), PMI was preceded by a prolonged (>24 h) period of increased cTnI, and in 21 patients (2%) the increase in cTnI lasted less than 24 h. Abnormal but low postoperative cTnI was associated with increased mortality and could lead to MI. The authors concluded that they had identified two different types of PMI, early and delayed (fig. 2).The fact that, in the cohort studied by Lee et al. ,2890% of patients with cTnT increases did not have clinical complications during the perioperative follow-up raised the question whether these values were false-positive results or evidence of subclinical myocardial injury. To address this issue, Lopez-Jimenez et al. 34collected 6-month follow-up data on a subcohort of 772 patients from the previous study. During the follow-up period, there were 19 (2.5%) major cardiac complications. A cTnT value more than 0.1 ng/ml was an independent correlate of cardiac events, whereas CK-MB was not correlated with postdischarge cardiac events.Badner et al. 35intensively monitored isoenzyme and electric activity of the heart for the first 7 postoperative days in 323 patients with ischemic heart disease, aged 50 yr or older, and undergoing noncardiac surgery. After surgery, patients had daily clinical assessments, electrocardiograms, and measurements of CK, CK-MB, and cTnT (not used in the first 92 patients) on the operative night, twice daily on PODs 1–4, and then daily on days 5–7. The criteria for PMI diagnosis were designed to require the presence of an indicator of high sensitivity (increased total CK) and at least two indicators of high specificity (increased CK-MB, increased cTnT, Q waves, or a positive result of a pyrophosphate scan). The authors observed a 6% incidence for PMI using these criteria. With 14 of 18 events occurring during the first postoperative night, they corroborated the finding that PMI is an early postoperative event in patients with known ischemic heart disease. Use of TnT increase as a sole criterion for the diagnosis of PMI would have nearly doubled the incidence and moved the peak of event occurrence to the first POD. Interestingly, 1-year follow-up suggested that patients with silent PMIs have similar short-term outcomes as those with symptomatic PMIs.Neill et al. 36evaluated the changes in cardiac protein concentrations (CK-MB, cTnT, and cTnI) after vascular or major orthopedic surgery in 80 patients older than 45 yr. The authors compared these changes as markers of postoperative cardiac complications with the incidence of ambulatory electrocardiographic changes for silent myocardial ischemia. Eight patients (10%) had major and 21 patients (27%) had minor postoperative complications. Both cTnT and cTnI showed high specificity for major complications, 96% and 97% respectively, but sensitivity was only 43% for cTnT and 29% for cTnI. There were no associations between postoperative ischemia and cardiac protein concentrations. At 3-month follow-up, cTnT correlated best with complications.The ideal discrimination value of cTnI between the "complicated and uncomplicated" patient groups was investigated by Godet et al. 37in 329 patients undergoing infrarenal aortic surgery. cTnI was measured at recovery and on PODs 1–3. MI was defined as new Q wave or prolonged ST-T depression for more than 2 days. Thirteen patients (4%) developed 19 relevant cardiac complications (cardiac failure, MI, and cardiac death) in the postoperative period. A cTnI level greater than 0.54 ng/ml was correlated with the occurrence of postoperative cardiac complications in the period until discharge. That cutoff yielded a sensitivity of 75% and a specificity of 89%. Late cardiac complications occurring in the first year after aortic surgery were not correlated with cTnI.Kim et al. 38found that increased cTnI levels were associated with a significantly increased risk of PMI and 6-month mortality in a group of 229 patients after major vascular surgery. They further reported a dose–response relation between cTnI concentration and mortality.According to the new universal definition of MI, any of the following criteria meets the diagnosis for MI: detection of rise or fall of cardiac biomarkers (preferably troponin) with at least one value above the 99th percentile of the upper reference limit together with evidence of myocardial ischemia with at least one of the following: symptoms of ischemia; electrocardiogram changes indicative of new ischemia (new ST-T changes or new left bundle branch block); development of pathologic Q waves in the electrocardiogram; and imaging evidence of new loss of viable myocardium or new regional wall motion abnormality.39However, it is important to keep in mind that nearly all the well-accepted studies of clinical risk stratification are based at least in part on diagnosis of PMI using adaptations of the World Health Organization definition, which requires any two of three criteria: ischemic symptoms, electrocardiographic changes, and increased CK-MB levels.In summary, the available studies highlight the difficulty of using cardiac-specific troponin to distinguish myocardial damage from infarction. Commonly, troponin increase alone is mistakenly equated with the diagnosis of MI. However, many conditions may be associated with increased troponin levels, including neurologic injury, brain death, hemorrhagic shock, cardiac trauma, sepsis, hypotension, renal insufficiency, pulmonary embolism, heart failure, and any other condition with increased ventricular wall stress.40–44Furthermore, although recently any increase in troponin in the appropriate clinical setting had been considered indicative of myocardial necrosis rather than ischemia, results from the Protein Markers of Ischemia using Proteomic Testing—TIMI 35 study showed that transient stress-induced myocardial ischemia is associated with a quantifiable increase in circulating troponin that is detectable with a novel, ultrasensitive cTnI assay.45Another issue that remains to be addressed is use in terms of guiding aggressiveness of care. Even if we believe that there is value in perioperative surveillance looking for troponin leakage in the absence of other criteria for MI, the question remains whether early therapy could affect outcome in terms of morbidity and mortality either in the perioperative period or after discharge.The new generation of hs cTn-assays has been shown to be superior to the standard troponin assays for early diagnosis of MI in two recently published studies.46,47However, these studies did not assess the effect of the sensitive troponin assays on clinical management. Furthermore, it remains to be proven whether the results from a group of patients with a high pretest probability can be translated to postsurgical conditions.Consistently performing better than traditional clinical risk scores and preoperative diagnostic tests, the natriuretic peptides clearly hold promise as a relatively cheap and noninvasive risk stratification tool, perhaps both pre- and postoperatively.48Hs C-reactive protein has been shown to be predictive of both immediate postoperative outcome49and significantly decreased overall survival50in the setting of coronary artery bypass surgery.Another interesting approach may be the simultaneous measurement of multiple biomarkers. Goei et al. recently demonstrated that both hs C-reactive protein and NT-pro-brain natriuretic peptide have additional value in the prediction of postoperative cardiac events in vascular surgery patients to cardiac risk factors alone. The integrated use of both NT-pro-brain natriuretic peptide and hs C-reactive protein was able to improve cardiac risk stratification.51Fellahi et al. 52assessed the multiple marker approach in cardiac surgery. Their recently published study showed that simultaneous measurement of cTnI, brain natriuretic peptide, and C-reactive protein improves the risk assessment of long-term adverse cardiac outcome after cardiac surgery.The evidence to guide the rational use of perioperative cardiac monitoring, electrocardiograms, and troponins is limited, and further evaluation regarding the optimal strategy is required. On the basis of the current evidence, in patients without documented coronary artery disease, surveillance should be restricted to those who develop perioperative signs of cardiovascular dysfunction. In patients with high or intermediate clinical risk who have known or suspected coronary artery disease and who are undergoing high- or intermediate-risk surgical procedures, serial 12-lead electrocardiograms should be obtained at baseline, immediately after the surgical procedure and on PODs 1 and 2. Consideration should be given to the use of cardiac-specific troponins for the first 4 days after surgery.In light of all the areas of uncertainty concerning the clinical value of measuring troponin leakage, the 2007 update of the American College of Cardiology/American Heart Association Perioperative Evaluation Guidelines the for postoperative troponin measurement to patients with electrocardiographic changes or chest pain typical of acute coronary syndrome of of Guidelines for preoperative cardiac risk assessment and perioperative cardiac in noncardiac surgery that were published in not sampling to cardiac

Biomarkers in the triage of chest pain: are we making progress?

ecently, the European Society of Cardiology (ESC) and the American College of Cardiology (ACC) convened a conference to discuss refinements in the diagnosis of acute myocardial infarction.The panel on biochemistry considered issues related to the use of marker proteins.We were guided predominantly by the science of the area.We were also cognizant of the impact that changes in the standards would have on epidemiology, clinical trials, education of physicians, and patient care.Our recommendations will be incorporated, with the recommendations of the other panels, into a position paper for the ESC and the ACC.However, the members of the biochemistry group decided to express the opinions we felt were important in this area independently.Our thinking does not represent the position of the ESC, the ACC, or of the conjoint task force.Many modifications of the original World Health Organization criteria for acute myocardial infarction 1 have been accepted and incorporated into the ESC/ACC criteria; some deletions have also occurred.Until recently, most markers were detected using enzymatic activity; detection of the protein concentration now is preferred.Thus, it is more appropriate to refer to molecules released into the circulation as a consequence of cardiac injury as biochemical diagnostic markers or biomarkers.In this editorial, we emphasize issues related to the biochemical diagnosis of acute myocardial infarction.New and improved plasma biomarkers (troponins) with better sensitivity and specificity will be emphasized in preference to markers such as total creatine kinase (CK), CK-MB, lactate dehydrogenase, and aspartate aminotransferase.Rapid assays for the early detection of infarction that may be helpful will be delineated, and the use of the troponin markers to aid in the risk stratification of patients with acute coronary syndromes will be recommended. Specific Recommendations Biomarker IncreasesDetectable increases in the biomarkers of cardiac injury are indicative of injury to the myocardium, but elevations are not synonymous with an ischemic mechanism of injury.Therefore, increases do not now and did not in the past mandate a diagnosis of myocardial infarction. 2,3 Cardiac Troponins Are Preferred MarkersCardiac troponins (I or T) are the preferred markers for the diagnosis of myocardial injury. 4 -6 The improved tissue specificity of the troponins compared with CK-MB and other conventional markers is well established.Initially, because of assay difficulties, some questioned the specificity of cardiac troponin T (cTnT), especially in patients with renal failure. 7However, immunohistochemical and molecular studies on the skeletal muscle from such patients has established that the isoforms of cTnT that are re-expressed in response to injury are not detected with the second and third generation assays for cTnT. 8,9Thus, increased plasma levels of cTnI or cTnT are highly specific for release from the myocardium.This advantage has been established in clinical studies.It is now clear that when conjoint skeletal muscle and cardiac injury is present, the improved specificity of the troponins reduces the number of false-positive results while maintaining high sensitivity. 6,10 -12 This improved specificity is coupled with improved sensitivity. 4 -6,13 This fact, along with the prolonged time window 14,15 during which troponin markers are elevated, allow for the detection of a larger number of patients at risk for subsequent adverse cardiac events. 16 -19 For these reasons, troponins should be the preferred marker for diagnostic use.Laboratories should move as rapidly as feasible to implement cTnI or cTnT as the new standard.For clinical laboratories that cannot move as rapidly as others to implement this new standard, CK-MB values should be used. 20CK-MB has less tissue specificity than the troponins 8,11 ; however, the data documenting its specificity for irreversible injury is more robust. 21Most clinicians and laboratorians prefer to use mass assays.Several markers should no longer be used to evaluate cardiac disease.These include total CK, aspartate aminotransferase, total lactate dehydrogenase, and lactate dehydrogenase isoenzymes.These markers have poor specificity for the detection of cardiac injury because of their wide tissue distribution.Because total CK has served as the gold standard for so many years, some may wish to continue to measure it to allow for comparisons over time.This is a reasonable rationale for those conducting trials and epidemiologists.If used, a high threshold for abnormality (Ն2-fold increase)

The development of rapid, automated, and accurate laboratory testing for creatine kinase MB (CK-MB) revolutionized the treatment of patients with acute cardiac events in the 1970s and 1980s.1 To clinicians, CK-MB values augmented a thorough history, physical, and ECG findings, and elevations rapidly became the gold standard for identifying cardiac injury.1 CK-MB allowed earlier diagnosis of acute myocardial infarction (AMI), and detection of reinfarction, and measurements could be used to provide a facile clinical estimate of infarct size. Elevations of CK-MB were never intended to be synonymous with myocardial infarction, only indicative of cardiac injury.1 However, because of the relative insensitivity of measurements, increased concentrations occurred predominantly with larger insults such those associated with acute ischemic heart disease. For that reason, AMI was rarely diagnosed, assuming appropriate timing of the samples, in the absence of a CK-MB elevation.2,3 CK-MB assays initially relied on the measurement of enzyme activity, but over time, improved accuracy and ease of use were established by the use of mass assays. Mass assays allowed earlier detection of abnormal values and improved both clinical sensitivity and specificity. However, mass assays unmasked an increased frequency of CK-MB elevations due primarily to skeletal muscle injury because of their increased sensitivity.4–6 Clinical use of the percent relative index was then initiated. This approach improved the specificity of elevations for cardiac muscle injury but was insensitive when concurrent cardiac injury and skeletal muscle injury were present because elevations from skeletal muscle often are of a large magnitude.7–10 A large number of analytical confounds such as macrokinases and interfering substances also were substantial problems with these assays.10,11 Attempts to standardize assays12 have been partially successful, but differences still exist between manufacturers and even between the same testing antibodies used on different analytical platforms (ie, …

Background: The early mortality rate from AMI is 30% with about half of them occurring within 1hour of disability. Although the mortality rate after admission for AMI has declined by 30% over the past decades, approximately 1 of every 25 patients who survive the initial hospitalization die in the first year after AMI. The gold standard for diagnosis of MI has been an elevated serum level of creatinine kinase – myocardial band (CK- MB), the cardiac-specific isoenzyme of CK. However, elevated CK-MB may not detect all myocardial necrosis. In patients who die suddenly after severe or silent episodes of ischemia, autopsies frequently reveal micronecrosis that was not reflected in routine CK-MB measurements. The present study was undertaken to know that serum Cardiac Troponin-I is more sensitive marker than serum CPK-MB in early diagnosis of acute myocardial infarction (AMI).Methods: The study was carried out in tertiary care hospital in Gulbarga. The study was undertaken with an aim to study that serum cardiac troponin-I (cTnl) is more sensitive than serum CK-MB in early diagnosis of acute myocardial infarction (AMI). The study was conducted on patients admitted with history of chest pain suggestive of AMI as diagnosed by WHO criteria to medicine ward of Basaveshwar Teaching and General Hospital, Gulbarga. The period of study was from June 2012 to June 2014. The sample size included 100 patients with history of chest pain suggestive of AMI, selected by simple random method.Results: Our results revealed that cardiac troponin I was more sensitive (62%) than CK-MB in overall cases admitted in between 6-24 hrs from the onset of chest pain. Maximum number (41%) of AMI patients were affected on the anterior wall followed by Inferior wall of AMI. 11 percent were affected with Antero lateral wall wereas 5 to 6 percent were affected with anteroseptal and global acute and right ventricular AMI was seen among 2 percent of patients. Anterior wall AMI was the significantly affected site with AMI (ʎ2:12.5, P:0.0004). The maximum number of acute myocardial infarctions were ST elevation myocardial infarctions. 28% of cases where CKMB is normal, the cTnI detects the AMI cases indicating its sensitivity.Conclusions: Cardiac troponin-I (cTnI) was more sensitive serum marker than CKMB in the early diagnosis of acute myocardial infarction (AMI). Anterior wall was the most significantly affected site of AMI. In the future, further improvements in analytical performance may open additional diagnostic windows.

Objective To explore the value of heart-type fatty acid-binding protein (H-FABP) in the early diagnosis of acute myocardial infarction (AMI). Methods Sixty confirmed AMI patients were observed, the data of H-FABP, cardiac troponin T (cTnT), creatine kinase MB (CK-MB) were detected in 0.05 ). There was no significant difference in the specificity among the three markers (P > 0.05). Conclusions H-FABP has more sensitivity and specificity in the early diagnosis of AMI. It is applicable in the screening of patients who suffered chest pain and the diagnosis of early AMI. Key words: Myocardial infarction; Cardiac markers; Heart-type fatty acid-binding protein

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Rapid and correct diagnosis of acute myocardial infarction (AMI) plays a crucial role in saving patients' life. Although some biomarkers (such as cardiac troponin and creatine kinase) are available for AMI diagnosis so far, there is still a clinical need for novel biomarkers, which can reliably rule in or rule out AMI immediately on admission. Circulating microRNAs (miRNAs) are a potential choice for novel biomarkers in AMI diagnosis and prognosis with high sensitivity and specificity. Circulating microRNAs are endogenous miRNAs that are detectable in whole blood, serum, or plasma in a highly stable form. Until now, around 20 circulating miRNAs were reported to be closely associated with AMI. In this minireview, we summarized recent available data on the correlation between circulating miRNAs and AMI. Some miRNAs, such as miR-208, miR-499, miR-133, and miR-1, were given special attention, since they may have a potential prospect in diagnosis and prognosis of AMI.

Comparing the diagnostic values of circulating microRNAs and cardiac troponin T in patients with acute myocardial infarction

To evaluate the value of cardiac troponin(cTn), myoglobin(Myo) combined with heart-type fatty acid-binding protein(H-FABP) detection in the diagnosis of early acute myocardial infarction(AMI). This study was a clinical comparative study. Eighty patients with AMI hospitalized in Tangshan Workers' Hospital were selected as study group, and another 80 individuals receiving normal physical examination were selected as control group from September 20, 2021 to September 20, 2022. The concentrations of cTn, Myo and H-FABPP, diagnostic indicators, the sensitivity and specificity of combined diagnosis, as well as the diagnostic efficacy for AMI were compared between the two groups. The levels of cTn, Myo and H-FABPP in the study group were significantly higher than those in the control group(P= 0.00). Multivariate logistic regression analysis showed that cTn, Myo and H-FABP were all relevant indicators for AMI. H-FABP alone has better diagnostic efficacy for AMI. The area under the curve of their combined detection, the specificity, and the sensitivity were higher than those of cTn, Myo and H-FABP alone, indicating that their combined application has the best diagnostic efficiency. cTn, Myo and H-FABP levels were positively correlated with Glu, TC, LDL-C and hs-CRP levels(P< 0.01), while negatively correlated with HDL level(P< 0.01). The combined detection of cardiac markers such as cTn, Myo and H-FABP presents higher sensitivity and specificity in the diagnosis of AMI compared with any single detection, and can provide better data support for the definite diagnosis of AMI, with high clinical application value.

Acute myocardial infarction (AMI) is a cardiovascular diseases characterized by myocardial necrosis resulting from acute and persistent obstruction of a coronary artery. AMI accounts for one third of overall cardiovascular diseases deaths, exceeding the mortality of any single tumor. It shows an increasing trend year by year1-2. Cardiac troponin T is the gold standard for diagnosis of AMI, but has insufficient specificity at early times3-4. Herein, we report a three-biomarker strategy, including cardiac troponin I, heart type fatty acid binding protein, and copeptin, for rapid, accurate and early diagnosis of AMI via a multiplex electrochemiluminescence immunoarray coupled with robust machine learning5. In a >200 subject pilot trial, the three-biomarker joint model achieved 100% sensitivity and specificity across a broad patient population with chest pain, including those patients within three hours of symptom onset. This study is very important for the diagnosis, medical treatment and prognoses of AMI, which holds the potential to minimize AMI mortality as well as to lower medical expenditure. Keywords: Acute Myocardial Infarction, Electrochemiluminescence, Sensor, Diagnosis. Reference [1] Reed, G. W.; Rossi, J. E.; Cannon, C. P. Acute myocardial infarction. Lancet 2017, 389, 197-210.[2] Sarkar, K.; Cai, Z. Q.; Gupta, R.; Parajuli, N.; Fox-Talbot, K.; Darshan, M. S.; et al. Hypoxia-inducible factor 1 transcriptional activityin endothelial cells is required for acute phasecardioprotection induced by ischemic preconditioning. Proc. Natl. Acad. Sci. USA. 2012, 109(26), 10504-10509.[3] Mullany, L. K.; Rohira, A. D.; Leach, J. P.; et al. A steroid receptor coactivator stimulator (MCB-613) attenuates adverse remodeling after myocardial infarction. Proc. Natl. Acad. Sci. USA. 2020, 117(49), 31353-31364.[4] Thygesen, K.; Joseph, S. A.; Allan, S. J.; et al. Fourth universal definition of myocardial infarction. Circulation 2018, 13, e618-e651.[5] Guo M., Du D., Wang J., et al. Three-biomarker joint strategy coupled with robust machine learning for early and accurate diagnosis of acute myocardial infarction. Chem. & Biomed. Imaging. 2023, 1,179-185.

How Low Can We Go? The High-Sensitivity Cardiac Troponin Debate

Use of Neutrophil Count in Early Diagnosis and Risk Stratification of AMI

The Third Universal Definition of Myocardial Infarction (MI) requires cardiac myocyte necrosis with an increase and/or a decrease in a patient's plasma of cardiac troponin (cTn) with at least one cTn measurement greater than the 99(th) percentile of the upper normal reference limit during: (1) symptoms of myocardial ischemia; (2) new significant electrocardiogram (ECG) ST-segment/T-wave changes or left bundle branch block; (3) the development of pathological ECG Q waves; (4) new loss of viable myocardium or regional wall motion abnormality identified by an imaging procedure; or (5) identification of intracoronary thrombus by angiography or autopsy. Myocardial infarction, when diagnosed, is now classified into five types. Detection of a rise and a fall of troponin are essential to the diagnosis of acute MI. However, high sensitivity troponin assays can increase the sensitivity but decrease the specificity of MI diagnosis. The ECG remains a cornerstone in the diagnosis of MI and should be frequently repeated, especially if the initial ECG is not diagnostic of MI. There have been significant advances in adjunctive pharmacotherapy, procedural techniques and stent technology in the treatment of patients with MIs. The routine use of antiplatelet agents such as clopidogrel, prasugrel or ticagrelor, in addition to aspirin, reduces patient morbidity and mortality. Percutaneous coronary intervention (PCI) in a timely manner is the primary treatment of patients with acute ST segment elevation MI. Drug eluting coronary stents are safe and beneficial with primary coronary intervention. Treatment with direct thrombin inhibitors during PCI is non-inferior to unfractionated heparin and glycoprotein IIb/IIIa receptor antagonists and is associated with a significant reduction in bleeding. The intra-coronary use of a glycoprotein IIb/IIIa antagonist can reduce infarct size. Pre- and post-conditioning techniques can provide additional cardioprotection. However, the incidence and mortality due to MI continues to be high despite all these recent advances. The initial ten year experience with autologous human bone marrow mononuclear cells (BMCs) in patients with MI showed modest but significant increases in left ventricular (LV) ejection fraction, decreases in LV end-systolic volume and reductions in MI size. These studies established that the intramyocardial or intracoronary administration of stem cells is safe. However, many of these studies consisted of small numbers of patients who were not randomized to BMCs or placebo. The recent LateTime, Time, and Swiss Multicenter Trials in patients with MI did not demonstrate significant improvement in patient LV ejection fraction with BMCs in comparison with placebo. Possible explanations include the early use of PCI in these patients, heterogeneous BMC populations which died prematurely from patients with chronic ischemic disease, red blood cell contamination which decreases BMC renewal, and heparin which decreases BMC migration. In contrast, cardiac stem cells from the right atrial appendage and ventricular septum and apex in the SCIPIO and CADUCEUS Trials appear to reduce patient MI size and increase viable myocardium. Additional clinical studies with cardiac stem cells are in progress.

Cardiac troponin (cTn) is the biomarker of choice for the diagnosis of acute myocardial infarction (MI); use of this biomarker has centered around the 99th percentile upper reference limit (URL) for healthy populations. Recent development and regulatory approval of high-sensitivity cardiac troponin (hs-cTn) assays have required a fresh look at utilization of the 99th percentile URL. This review covers issues regarding the 99th percentile URL and approaches for use of cTn as biomarker for detecting cardiac injury and diagnosis of acute myocardial infarction. Development of hs-cTn assays has allowed determination and use of sex-specific 99th percentile URLs for assessing cardiac injury and increased the utility of cTn values below the 99th percentile URL. This improved analytical performance for hs-cTn assays has allowed for development of accelerated diagnostic protocols (ADPs) for rapid assessment and disposition of patients based on serial sampling of cTn for use in acute MI diagnosis as soon as 0-1h after clinical presentation. The 99th percentile URLs of cTn is essential for detecting cardiac injury; however, use of the 99th percentile URLs in the era of hs-cTn results may be modified. ADPs have the potential to substantially decrease the time many patients spend under evaluation for acute MI, thereby potentiating improvement in patient satisfaction, decreased healthcare costs, and reducing the burden on emergency departments.