High-sensitivity detection of cardiac troponin I with UV LED excitation for use in point-of-care immunoassay.

High-sensitivity cardiac troponin assay development enables determination of biological variation in healthy populations, more accurate interpretation of clinical results and points towards earlier diagnosis and rule-out of acute myocardial infarction. In this paper, we report on preliminary tests of an immunoassay analyzer employing an optimized LED excitation to measure on a standard troponin I and a novel research high-sensitivity troponin I assay. The limit of detection is improved by factor of 5 for standard troponin I and by factor of 3 for a research high-sensitivity troponin I assay, compared to the flash lamp excitation.

Autoantibodies to cardiac troponin associate with higher initial concentrations and longer release of troponin I in acute coronary syndrome patients.

Background: Cardiac troponin (cTn) is an established marker of myocardial infarction. Pronounced heterogeneity and the minute amounts released into the circulation constitute significant challenges for cTn detection. Recently, autoantibody formation to cTn was shown to be common and to interfere with immunoassay performance.

Early markers of myocardial injury: cTnI is enough.

Background: We compared the early diagnostic and prognostic performance of a highly sensitive cardiac troponin I (cTnI) assay with heart-type fatty acid binding protein (H-FABP), in the early hours of acute coronary syndrome.

Methods: Serum samples of 293 patients were studied using the Abbott Architect cTnI assay and the H-FABP assay. Special attention was paid to the diagnostic and prognostic value of admission blood samples taken <24 h after symptom onset.

Clinical significance of troponin I efflux and troponin autoantibodies in patients with dilated cardiomyopathy.

Background: The appearance of circulating autoantibodies against cardiac troponin I (cTnAbs) in patients with heart failure has been reported. We sought to evaluate the role of circulating cardiac troponin I (cTnI) and cTnAbs in the pathophysiology and prognosis of idiopathic dilated cardiomyopathy.

Methods And Results: Circulating concentrations of cTnI and the presence of cTnAbs were determined in 95 patients with idiopathic dilated cardiomyopathy.

Sensitive protein detection via triple-binder proximity ligation assays.

The detection of weakly expressed proteins and protein complexes in biological samples represents a fundamental challenge. We have developed a new proximity-ligation strategy named 3PLA that uses three recognition events for the highly specific and sensitive detection of as little as a hundred molecules of the vascular endothelial growth factor (VEGF), the biomarkers troponin I, and prostate-specific antigen (PSA) alone or in complex with an inhibitor--demonstrating the versatility of 3PLA.

Present and future biochemical markers for detection of acute coronary syndrome.

The use of biochemical markers in the diagnosis and management of patients with acute coronary syndrome has increased continually in recent decades. The development of highly sensitive and cardiac-specific troponin assays has changed the view on diagnosis of myocardial infarction and also extended the role of biochemical markers of necrosis into risk stratification and guidance for treatment. The consensus definition of myocardial infarction places increased emphasis on cardiac marker testing, with cardiac troponin replacing creatine kinase MB as the "gold standard" for diagnosis of myocardial infarction.

Utilization of recombinant Fab fragments in a cTnI immunoassay conducted in spot wells.

Objectives: To evaluate the performance of a new cTnI immunoassay utilizing site-specifically biotinylated recombinant Fab fragments on recently established spot wells.

Design And Methods: Two different cTnI-specific recombinant site-specifically biotinylated Fab fragments were produced. The performance of the new sandwich-type cTnI immunoassay in spot wells was evaluated in terms of binding capacity, assay kinetics and assay sensitivity and compared with a cTnI immunoassay carried out in conventional microtitration wells.

Negative interference in cardiac troponin I immunoassays by circulating troponin autoantibodies.

Background: There are numerous potential sources of interference in immunoassays. Our aim was to identify the blood component that causes negative interference in cardiac troponin I (cTnI) immunoassays based on antibodies against the central part of cTnI.

Methods: We isolated an interfering factor (IF) from a sample with low recovery of added cTnI, using several consecutive purification steps: caprylic acid precipitation, ammonium sulfate precipitation, and purification on Cibacron Blue gel and protein G columns.

Comparison of cardiac troponin I immunoassays variably affected by circulating autoantibodies.

Background: We recently provided evidence that circulating autoantibodies against cardiac troponin I (cTnI) or the troponin complex cause negative interference in cTnI immunoassays. By comparing three cTnI immunoassays, we further explored the phenomenon of circulating autoantibodies and their consequences in patient samples.

Methods: We developed a cTnI immunoassay with a novel assay design using three antibodies, two of which bind epitopes outside the stable, central part of cTnI.

Development of sensitive immunoassays for free and total human glandular kallikrein 2.

Background: Free and total human kallikrein 2 (hK2) might improve the discrimination between prostate cancer and benign prostatic hyperplasia. Concentrations of hK2 are 100-fold lower than concentrations of prostate-specific antigen (PSA); therefore, an hK2 assay must have a low detection limit and good specificity.

Methods: PSA- and hK2-specific monoclonal antibodies were used in solid-phase, two-site immunofluorometric assays to detect free and total hK2.

An interfering component in cardiac troponin I immunoassays-Its nature and inhibiting effect on the binding of antibodies against different epitopes.

Objectives: We recently reported on the occurrence of a common interfering factor (IF) that negatively affects determinations of cardiac troponin I (cTnI). The aim of the present investigation was to extend our initial finding by a detailed epitope-based determination of the location of IF and to reveal the approximate size and characteristics of IF.

Design And Methods: Two-site immunoassays using combinations of 16 monoclonal and 2 polyclonal cTnI antibodies and 1 monoclonal troponin C (TnC) antibody were used to measure the analytical recovery of cTnI or cTnI-TnC in serum samples.

Negative interference in cardiac troponin I immunoassays from a frequently occurring serum and plasma component.

Background: Cardiac troponin I (cTnI) is a sensitive marker of cardiac injury, but cTnI assays, like other immunoassays, are susceptible to interferences. We evaluated the presence of interfering substances by measuring the recovery of cTnI added to samples from volunteers and from patients with acute coronary syndromes (ACS).

Methods: We added a ternary complex of human cardiac troponin (30-500 microg/L) or cTnI from serum to samples from healthy volunteers and ACS patients.

Release patterns of pregnancy associated plasma protein A (PAPP-A) in patients with acute coronary syndromes.

Objective: Pregnancy associated plasma protein A (PAPP-A) has recently been shown to be associated with acute coronary syndromes (ACS). The goal of this study was to investigate its release patterns in patients with ACS.

Design: PAPP-A concentrations in plasma samples serially collected after admissions from 15 patients with ACS were measured.