Validation of NACB and IFCC guidelines for the use of cardiac markers for early diagnosis and risk assessment in patients with acute coronary syndromes

Rapid and Sensitive Detection of Cardiac Troponin I for Point-of-Care Tests Based on Red Fluorescent Microspheres

A reliable lateral flow immunoassay (LFIA) based on a facile one-step synthesis of single microspheres in combining with immunochromatography technique was developed to establish a new point-of-care test (POCT) for the rapid and early detection of cardiac troponin I (cTnI), a kind of cardiac specific biomarker for acute myocardial infarction (AMI). The double layered microspheres with clear core-shell structures were produced using soap-free emulsion polymerization method with inexpensive compounds (styrene and acrylic acid). The synthetic process was simple, rapid and easy to control due to one-step synthesis without any complicated procedures. The microspheres are nanostructure with high surface area, which have numerous carboxyl groups on the out layer, resulting in high-efficiency coupling between the carrier and antibody via amide bond. Meanwhile, the red fluorescent dye, Nile-red (NR), was wrapped inside the microspheres to improve its stability, as well to reduce the background noise, because of its higher emission wavelength than interference from real plasma samples. The core-shell structures provided different functional areas to separate antibody and dyes, so the immunoassay has highly sensitive, wide working curves in the range of 0–40 ng/mL, low limits of detection (LOD) at 0.016 ng/mL, and limits of quantification (LOQ) at 0.087 ng/mL with coefficient of variations (CV) of 10%. This strategy suggested an outstanding platform for LFIA, with good reproducibility and stability to straightforwardly analyze the plasma samples without washing steps, thereby reducing the operating procedures for non-professionals and promoting detection efficiency. The whole detection process can be completed in less than 15 min. This novel immunoassay offers a reliable and favorable analytical result by detecting the real samples, indicating that it holds great potential as a new alternative for biomolecule detection in complex samples, for the early detection of cardiac specific biomarkers.

Cardiac biomarkers - the old and the new: a review

Biomarkers are biological parameters that can be objectively measured and quantified as indicators of normal biologic processes, pathogenic processes, or responses to a therapeutic intervention. Typically thought of as disease process screening, diagnosing, or monitoring tools, biomarkers may also be used to determine disease susceptibility and eligibility for specific therapies. Cardiac biomarkers are protein components of cell structures that are released into circulation when myocardial injury occurs. They play a pivotal role in the diagnosis, risk stratification, and treatment of patients with chest pain and suspected acute coronary syndrome and those with acute exacerbations of heart failure. Cardiac markers are central to the new definition of acute myocardial infarction put forward by the American College of Cardiology and the European Society of Cardiology. Active investigation has brought forward an increasingly large number of novel candidate markers but few have withstood the test of time and become integrated into contemporary clinical care because of their readily apparent diagnostic, prognostic, or therapeutic utility.

Diagnostic potential of phosphorylated cardiac troponin I as a sensitive, cardiac-specific marker for early acute coronary syndrome: Preliminary report

BACKGROUND

Cardiac troponin I (cTnI) has low sensitivity in the early hours of acute coronary syndrome (ACS). For patients with early ACS symptoms, we determined the diagnostic potential of an immunoassay for phosphorylated cTnI (PO(4)-cTnI).

METHODS

In a prospective study of 61 emergency department patients with suspected ACS, we compared a novel plasma immunoassay for PO(4)-cTnI to cTnI overall and in a subgroup with symptoms < or =4 h duration (n = 31). Admission PO(4)-cTnI and cTnI assays (thresholds determined by ROC curve) were analyzed in a blinded fashion against the clinical, ECG and coronary angiographic diagnosis of ACS.

RESULTS

Overall, PO(4)-cTnI sensitivity was significantly higher than cTnI (82% vs. 50%, respectively, P < 0.05) and PO(4)-cTnI specificity was 81% (n = 61). Addition of PO(4)-cTnI to cTnI improved sensitivity to 91% vs. 50% for cTnI alone (P < 0.001). In the < or =4 h subgroup (n = 31), PO(4)-cTnI sensitivity was significantly higher than cTnI (79% vs. 26%, respectively, P < 0.01) and PO(4)-cTnI specificity was 75%. In the same < or =4 h subgroup, addition of PO(4)-cTnI to cTnI improved sensitivity to 84% vs. 26% for cTnI alone (P = 0.001).

CONCLUSIONS

The results suggest that PO(4)-cTnI, alone or in combination with cTnI, warrants further investigation as a sensitive, cardiac-specific diagnostic tool for early ACS.

Determination of myoglobin based on its enzymatic activity by stopped-flow spectrophotometry

A new method has been developed for the determination of myoglobin (Mb) based on its enzymatic activity for the oxidation of o-phenylenediamine (OPDA) with hydrogen peroxide. Stopped-flow spectrophotometry was used to study the kinetic behavior of the oxidation reaction. The catalytic activity of Mb was compared to other three kinds of catalyst. The time dependent absorbance of the reaction product, 2,3-diamimophenazine (DAPN), at a wavelength of 426 nm was recorded. The initial reaction rate obtained at 40 degrees C was found to be proportional to the concentration of Mb in the range of 1.0 x 10(-6) to 4.0 x 10(-9)mol L(-1). The detection limit of Mb was found to be 9.93 x 10(-10)mol L(-1). The relative standard deviations were within 5% for the determination of different concentrations of Mb. Excess of bovine serum albumin (BSA), Ca(II), Mg(II), Cu(II), glucose, caffeine, lactose and uric acid did not interfere.

Prognostic implications of elevated whole blood choline levels in acute coronary syndromes

Troponins I and T represent the current biomarker standard for diagnosis of myocardial infarction. Even small increases of cardiac troponins have prognostic implications, but not all patients at risk are correctly classified, particularly at admission. We identified elevated whole-blood choline as a promising marker and performed a prospective study of 327 patients with a suspected acute coronary syndrome that focused on the analysis of troponin-negative patients. Diagnostic classification of patients and the definition of troponin cutoffs were performed according to the new European Society of Cardiology/American College of Cardiology criteria. Blood was sampled serially and choline was measured using high-performance liquid chromatography mass spectrometry in whole blood. Patients were followed for 30 days. In patients with negative troponin I test results at admission (n = 250), choline was a predictor of cardiac death and nonfatal cardiac arrest (hazard ratio 6.0, p = 0.003), life-threatening arrhythmias (hazard ratio 3.75, p = 0.004), heart failure (hazard ratio 2.87, p = 0.002), and coronary angioplasty (hazard ratio 2.57, p = 0.001). In multivariate analysis of troponin-negative patients, choline was the strongest predictor of cardiac death or arrest (odds ratio 6.05, p = 0.01). Choline was not a marker for myocardial necrosis but indicated high-risk unstable angina in patients without acute myocardial infarction (sensitivity 86.4%, specificity 86.2%). Thus, an increased concentration of choline at hospital admission is a predictor of adverse cardiac events in patients with suspected acute coronary syndromes. Whole blood choline may be useful for early risk stratification of these patients, particularly if troponin results are negative on admission.

Acute coronary syndrome: biochemical strategies in the troponin era

New biomarkers, such as cardiac troponins, have a major role to play for cost-effective management of individuals with acute chest pain and suspected coronary syndrome, and the laboratory is now poised to assume a vital role in assessing damage and determining prognosis. The redefined biochemical criterion proposed to classify acute coronary syndrome patients presenting with ischemic symptoms as patients with myocardial infarction is heavily predicated on an increased troponin concentration in blood. In an era of evidence-based medicine, we can no longer overlook the diagnostic and prognostic benefits provided by the measurement of these highly sensitive and specific proteins.

Guidelines and Algorithms: Perceptions of Why and When They Are Successful and How to Improve Them

Medicine is increasingly complex, a reality created by the explosion of knowledge during the last 50 years. The cost of applying this knowledge creates a daunting economic challenge. As a result, there has been a profusion of guidelines intended to influence medical practice. This report explores the interrelated issues and concepts that impact the value and success of guidelines. These include medical quality and error, compliance, and the impact on outcomes in an evidence-based medicine context. Lessons learned from previous guidelines must be understood in relation to human behavior. Legal implications of the guidelines must be considered because both an increase and a decrease in liability can be anticipated. Many products have been labeled “advocacy guidelines” with a negative context. They are believed to express motivation rather than optimizing care. The ideal of professionalism is challenged, and there is potential for the growing use of guidelines in enforcing punitive actions. Constructive experience has emphasized the appropriate required elements for practice guidelines: a systematic review of the literature, an assessment of the volume and level of the evidence, and development of a review process by an appropriate multidisciplinary group for consistency, clinical impact, and resource implications leading to clearly stated and reasonable recommendations. The dissemination of guidelines, beyond conventional publication in a journal, will impact the success of the intended outcomes. The exploitation of electronic avenues, including the Internet and the evolving interactive electronic medical record, seems to be essential for future success in these endeavors.