Proposals from the IFCC Committee on Standardization of Markers of Cardiac Damage (C-SMCD): Strategies and concepts on standardization of cardiac marker assays

Serum biochemical evaluation following administration of imidazolyl thiazolidinedione in streptozotocin-induced diabetic rats

BACKGROUND

Diabetes mellitus represents a prominent global health concern, characterized by a rising prevalence rate. Type 2 Diabetes Mellitus (T2DM) is purported to be associated with an intricate interplay of genetic, environmental, and lifestyle factors. While some progress have been made in T2DM management, controlling associated complications remains a great challenge in medicine.

OBJECTIVES

This study investigated a synthesized Imidazolyl Thiazolidinedione antidiabetic agent (PA9), focusing on serum parameters.

METHODS

Streptozotocin-induced diabetic rats (n = 6) were subjected to orally treatment with PA9 (synthesized by Shakour et al. in an equal dose of a standard drug, 0.011 mmol/kg). The study conducted to measure some specific serum factors, including lipid profiles, liver and kidney enzymes, cardiac enzymes, and oxidative stress markers, both before and after treatment.

RESULTS

The study findings indicated that PA9 effectively ameliorates hyperlipidemia by significantly reducing total cholesterol and triglyceride levels in serum. Additionally, PA9 demonstrated hepatoprotective effects against TZD-induced injuries, as evidenced by decreased levels of alanine transaminase and, alkaline phosphatase. In addition, PA9 also exhibited a modulatory effect on a cardiac injury marker, creatine kinase MB. Moreover, PA9 demonstrated antioxidant properties by reducing oxidative stress markers and enhancing the activities of catalase, thiol, and superoxide dismutase.

CONCLUSIONS

The synthesized TZD compound (PA9) stands out as a highly promising agent for the management of diabetes. Its significant antihyperlipidemic effects, preventive influences on organ injuries, and demonstrated efficacy in reducing oxidative stress marker (SOD) make it therapeutic agent in diabetes management. This study lays the groundwork for innovative strategies in diabetes management.

Electrochemical Immunosensor for Cardiac Troponin I Detection Based on Covalent Organic Framework and Enzyme-Catalyzed Signal Amplification

Herein, a highly sensitive electrochemical immunosensor was presented for the cardiac troponin I (cTnI) determination using a multifunctional covalent organic framework-based nanocomposite (HRP-Ab2-Au-COF) as the signal amplification probe. The spherical COF with a large surface area was synthesized in a short time by a simple solution-based method at room temperature. The good biocompatibility, low toxicity, and high stability in water of the COF guarantee its application in biosensing. Besides, its high porosity makes it an excellent carrier for loading abundant horseradish peroxidase (HRP). The modified gold nanoparticles on the surface of COF not only provide a load platform for secondary antibody (Ab2) but also improve the conductivity of COF. Under the synergistic effect of the hydrogen peroxide (H₂O₂) and HRP, hydroquinone (HQ) in the solution is catalytically oxidized to benzoquinone (BQ), which is then reduced on the electrode surface to generate the electrochemical signal. The designed probes not only show the specific recognition behavior of Ab2 to cTnI but also improve the sensitivity of the biosensing system due to the signal amplification caused by the excellent enzyme catalytic performance of HRP. Based on the H₂O₂-HRP-HQ signal amplification system, the biosensor for cTnI was fabricated and exhibited a linear response as a function of logarithmic cTnI concentration ranging from 5 pg/mL to 10 ng/mL, and the detection limit was 1.7 pg/mL. Moreover, the biosensor exhibited excellent recovery and reproducibility in the actual sample testing. This work provided a simple approach to determine cTnI quantitatively in practical samples and broadened the utilization scope of the COF-based nanocomposite in the electrochemical immunosensor.

Commutability of reference and control materials: an essential factor for assuring the quality of measurements in Laboratory Medicine

Traceability to a common reference ensures equivalence of results obtained by different assays. Traceability is achieved by an unbroken sequence of calibrations, using reference materials (RMs) that must be commutable. Using non-commutable RMs for calibration will introduce a bias in the calibrated method producing incorrect results for clinical samples (CS). Commutability was defined in 1973 as “the ability of an enzyme material to show inter-assay activity changes comparable to those of the same enzyme in human serum” and later extended as a characteristic of all RMs. However, the concept is still poorly understood and appreciated. Commutability assessment has been covered in CLSI guidelines and requires: (a) selection of 20 CS spanning the relevant concentration range; (b) analysis of both RM and CS with the pair of procedures; (c) data elaboration using regression analysis and calculation if RM fall within the 95% prediction interval defined by CS. This approach has been criticized and to improve it The International Federation of Clinical Chemistry and Laboratory Medicine established a working group that recently finalized recommendations. Commutability is also a requirement for the applicability of external quality assessment (EQA) results in the evaluation of the performance of participating laboratories in terms of standardization of their measurements. Unfortunately, EQA materials are usually not validated for commutability.

The quest for equivalence of test results: the pilgrimage of the Dutch Calibration 2.000 program for metrological traceability

Calibration 2.000 was initiated 20 years ago for standardization and harmonization of medical tests. The program also intended to evaluate adequate implementation of the In Vitro Diagnostics (IVD) 98/79/EC directive, in order to ensure that medical tests are fit-for-clinical purpose. The Calibration 2.000 initiative led to ongoing verification of test standardization and harmonization in the Netherlands using commutable external quality assessment (EQA)-tools and a type 1 EQA-design, where feasible. National support was guaranteed by involving all laboratory professionals as well as laboratory technicians responsible for EQA and quality officers. A category 1 EQA-system for general chemistry analytes, harmonizers for specific analytes like hGH and IGF-1, and commutable materials for other EQA-sections have been developed and structurally introduced in the EQA-schemes. The type 1 EQA-design facilitates the dialogue between individual specialists in laboratory medicine and the IVD-industry to reduce lot-to-lot variation and to improve standardization. In such a way, Calibration 2.000 sheds light on the metrological traceability challenges that we are facing and helps the laboratory community to get the issues on the table and resolved. The need for commutable trueness verifiers and/or harmonizers for other medical tests is now seen as paramount. Much knowledge is present in the Netherlands and for general chemistry, humoral immunology and protein chemistry, a few endocrinology tests, and various therapeutic drug monitoring (TDM) tests, commutable materials are available. Also the multi sample evaluation scoring system (MUSE) and the category 1 EQA-design offer many possibilities for permanent education of laboratory professionals to further improve the between and within laboratory variation and the test equivalence.

Assessment of myocardial involvement using cardiac troponin-I and echocardiography in rheumatic carditis in Izmir, Turkey

BACKGROUND

Acute rheumatic carditis is still a major problem in developing countries. Cardiac troponin-I (cTnI) has been identified as a sensitive and specific marker in the diagnosis of myocarditis in children and adults.

METHODS

A prospective study was performed using Doppler echocardiography and cTnI in order to detect myocardial involvement in 26 consecutive patients with acute rheumatic valvular disease. Patients were divided into two groups: group 1, rheumatic fever with carditis (n > 16); group 2, rheumatic fever without carditis (n > 10).

RESULTS

Clinically age, gender, body temperature, heart rate and white blood count did not differ significantly between the groups and the age-matched control group. C-reactive protein, erythrocyte sedimentation rate, anti-streptolysin-O were significantly different. Left ventricular fractional shortening was normal in all patients (group 1, 37 +/- 10%; group 2, 34 +/- 5%; NS). Left ventricular dimensions were larger in group 1, in which all patients except two had moderate to severe mitral and/or aortic valvular regurgitation (5.05 +/- 0.75 cm/m(2)) compared to group 2, in which none had valvular regurgitation (3.27 +/- 0.26 cm/m(2), P < 0.05). None of the patients in either group presented with or developed pericarditis. Mean cTnI was 0.12 +/- 0.034 ng/mL in group 2 and 0.077 +/- 0.02 in group 1, the difference of which was not statistically significant. Neither significant cTnI elevations nor echocardiographic systolic function abnormalities were found in the present patients with rheumatic carditis.

CONCLUSIONS

The present results indicate the absence of myocardial involvement in acute rheumatic carditis without congestive heart failure.

Beckman Access versus the Bayer ACS:180 and the Abbott AxSYM cardiac Troponin-I real-time immunoassays: an observational prospective study

Background

Reliability of cardiac troponin-I assays under real-time conditions has not been previously well studied. Most large published cTnI trials have utilized protocols which required the freezing of serum (or plasma) for delayed batch cTnI analysis. We sought to correlate the presence of the acute ischemic coronary syndrome (AICS) to troponin-I values obtained in real-time by three random-mode analyzer immunoassay systems: the Beckman ACCESS (BA), the Bayer ACS:180 (CC) and the Abbott AxSYM (AX).

Methods

This was an observational prospective study at a university tertiary referral center. Serum from a convenience sampling of telemetry patients was analyzed in real-time for troponin-I by either the BA-CC (Arm-1) or BA-AX (Arm-2) assay pairs. Presence of the AICS was determined retrospectively and then correlated with troponin-I results.

Results

100 patients were enrolled in Arm-1 (38 with AICS) and 94 in Arm-2 (48 with AICS). The BA system produced 51% false positives in Arm-1, 44% in Arm-2, with negative predictive values of 92% and 100% respectively. In Arm-1, the BA and the CC assays had sensitivities of 97% and 63% and specificities of 18% and 87%. In Arm-2, the BA and the AX assays had sensitivities of 100% and 83% and specificities of 11% and 78%.

Conclusions

In real-time analysis, the performance of the AxSYM and ACS:180 assay systems produced more accurate troponin-I results than the ACCESS system.

The measurement of cardiac markers: where should we focus?

Cardiac markers are presently a hot topic, with active debate on their use. They now have a major role for cost-effective management of acute chest pain and suspected acute coronary syndrome. The laboratory has a pivotal role in proper selection and interpretation of available markers, depending on the creation of evidence-based knowledge about test utilization and sources of variation. This article reviews this knowledge in the field of biomarkers determination and summarizes the major analytic and clinical issues, with reference to various recent recommendations of laboratory medicine and cardiology expert groups.

Cardiac troponin I: its contribution to the diagnosis of perioperative myocardial infarction and various complications of cardiac surgery

OBJECTIVE

To study the value of assaying cardiac troponin I (cTnI) for the early diagnosis of perioperative myocardial infarction (PMI) and various complications of cardiac surgery.

DESIGN

A prospective observational clinical study.

SETTING

Biochemical laboratory, anesthesia, and cardiac surgery department of Hôpital Broussais.

PATIENTS

Two hundred and sixty consecutive patients undergoing cardiac surgery.

INTERVENTIONS

All patients underwent coronary artery bypass grafting and/or valvular surgery under extracorporeal circulation. Per-operative and postoperative follow-up consisted of electrocardiogram, echocardiography (mainly by the transesophageal approach), and serial determinations of biochemical markers such as creatinine kinase-MB isoenzyme (CK-MB) and cTnI. PMI, new ST segment changes, and ventricular arrhythmias were considered postoperative adverse cardiac outcome.

MEASUREMENTS AND MAIN RESULTS

CTnI was measured before cardiopulmonary bypass (T0) and 12 and 24 hrs after (T12, T24). CK-MB was measured on arrival in the intensive care unit and on the first postoperative day (D1). Patients were divided into three groups according to the type of surgery: coronary artery bypass graft (CABG), valvular surgery (VS), or both procedures. The plasma CK-MB and cTnI concentrations were high in all patients after extracorporeal circulation because of aortic clamping or cardioplegia. The CK-MB and cTnI values were higher in the VS group than in the CABG group. Values peaked at T12 and fell by T24, except when PMI occurred. Eight patients developed a PMI. Patients with PMI had significantly higher cTnI levels at T12 and T24, and higher CK-MB values at D1 than patients without PMI. Cutoff values of cTnI for diagnosing PMI were >19 microg/L at T12 with 100% sensitivity and 73% specificity, and >36 microg/L at T24, with 100% sensitivity and 93% specificity. Lower cTnI values were highly suggestive of the absence of PMI after CABG and/or VS. Other complications such as ST segment changes, ventricular arrhythmias and cardiac failure were indicated by high cTnI levels at T12 and T24. Myocardial protective measures were associated with a nonsignificant increase in cTnI values.

CONCLUSIONS

CTnI is more sensitive and specific than CK-MB for diagnosing PMI and other forms of heart failure after cardiac surgery.

Recent approaches to the standardization of cardiac markers

The development of commercial assays for the determination of cardiac proteins has been one of the most important innovations in the field of cardiovascular diagnostics in the last decade. Some assays are, however, inadequately appraised prior to their introduction to clinical use. This paper focuses on some important preanalytical, analytical and interpretative problems, and summarizes the status of the ongoing local and international standardization efforts. The most urgent issue at the moment is the development of international reference materials, which can be used for the calibration of different assays, thus decreasing between-assay biases. In order to achieve comparability of test results, another important item is the standardization of the epitopes of the antibodies used for the assay development. Efforts to improve the precision of cardiac marker assays are also warranted. Finally, the effect of storage time and temperature on apparent marker concentration and the possible influence of different anticoagulants on measured marker values should clearly be evaluated.

Multicenter Evaluation of Five Assays for Myoglobin Determination

Background: Lacking assay standardization, different myoglobin methods may produce results that differ significantly.

Methods: A multicenter study was carried out to compare the analytical performance of five commercially available assays for myoglobin measurement. Linearity, imprecision, interferences, and method comparison were studied according to NCCLS guidelines, whereas reference values were determined following IFCC recommendations.

Results: The BNA and Opus showed relatively high imprecision (all but one total CV &gt;7.4%). Other assays showed lower CVs, but they varied among laboratories, particularly at a normal myoglobin concentration (Access, 6.0–11%; Hitachi, 3.8–5.8%; Stratus, 3.4–6.5%). Results were lower in anticoagulated samples on the Access, in heparin and citrate samples on the Stratus, and in citrate samples on the BNA and Opus, and increased in heparin and EDTA samples on the Hitachi. Use of separator gel produced results significantly lower (P &lt;0.001) on the Hitachi and higher (P = 0.016) on the Opus. Bilirubin, turbidity, and hemoglobin had no effect on evaluated methods, but rheumatoid factor affected the Access. In method comparisons, high correlation coefficients (≥0.98) were obtained. The Stratus gave higher results; however, the Access and BNA gave the lowest. The following upper reference limits (μg/L) for men and women, respectively, were obtained: Access, 70 and 52; BNA, 51 and 49; Hitachi, 67 and 58; Opus, 80 and 50; and Stratus, 86 and 63.

Conclusion: The possibility of high imprecision and marked disagreement among commercial myoglobin assays should be carefully considered in clinical practice.