Circulating cardiac troponin-I autoantibodies in human plasma and serum.
ABSTRACT We identified IgG reactive with human cardiac troponin-I (cTnI) in plasma and serum samples (N = 1930) from normal blood donors, and in sample cohorts characterized on the basis of clinical biomarkers associated with cardiac, infectious, and autoimmune diseases. cTnI and brain natriuretic peptide were the biomarkers chosen to reflect myocyte damage or left ventricular dysfunction, respectively. The infectious disease cohorts were serologically positive for antibodies to hepatitis B (natural infection), hepatitis C virus, and Chagas (i.e., T.cruzi). The autoimmune cohorts were represented by samples from diagnosed systemic lupus erythematosus (biomarker: dsDNA) and rheumatoid arthritis (biomarker: rheumatoid factor) subjects. The prevalence of IgG autoantibodies reactive with cTnI was high in the normal donor cohort (95/750, 12.7%). The prevalence in the other sample cohorts was not significantly different from that in the normal blood donors, with the exception of a slight increase in the rheumatoid factor cohort (28/137, 20.4%). The presence of anti-cTnI IgG in highly reactive samples was confirmed by inhibition with the antigen and further by screening with a library of peptides derived from the human cTnI amino acid sequence. Our data suggest that these autoantibodies are polyspecific, encompassing epitopes across the entire cTnI sequence, including the cardiac-specific amino terminal region.
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ABSTRACT: The laboratory measurement of cardiac troponin (cTn) concentration is a critical tool in the diagnosis of acute myocardial infarction (MI). Current cTnI assays produce different absolute troponin numbers and use different clinical cut-off values; hence cTnI values cannot be interchanged, with consequent confusion for clinicians. A recent Australian study compared patient results for seven cTnI assays and showed that between-method variation was approximately 2- to 5-fold. A major reason for poor method agreement is the lack of a suitable common reference material for the calibration of cTnI assays by manufacturers. Purified complexed troponin material lacks adequate commutability for all assays; hence a serum-based secondary reference material is required for cTnI with value assignment by a higher order reference measurement procedure. There is considerable debate about how best to achieve comparability of results for heterogeneous analytes such as cTnI, whether it should be via the harmonisation or the standardisation process. Whereas harmonisation depends upon consensus value assignment and uses those commercial methods which give the closest agreement at the time, standardisation comes closer to the true value through a reference measurement system that is based upon long-term calibration traceability. The current paper describes standardisation efforts by the International Federation of Clinical Chemistry and Laboratory Medicine Working Group on Standardization of cTnI (IFCC WG-TNI) to establish a reference immunoassay measurement procedure for cTnI of a higher order than current commercial immunoassay methods and a commutable secondary reference material for cTnI to which companies can reference their calibration materials.Pathology 01/2010; 42(5):402-8. · 2.38 Impact Factor
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ABSTRACT: Autoantibody against interferon is associated in many viral and non-viral diseases. This study aimed to determine the prevalence of anti-IFN-alpha autoantibodies in healthy Egyptian blood donors. The study included 558 (100 females (17.92%) and 458 males (82.08%)) Egyptian healthy blood donors who showed normal levels of liver enzymes and kidney tests and were conformed negative for hepatitis B surface antigen (HBsAg), hepatitis C virus (HCV) antibodies (Abs), HIV-1/2 Abs, anti-HBc and Treponema Abs. Autoantibody against IFN-alpha-1a and IFN-alpha-2b were screened using ELISA. Anti-IFN-alpha-1a positive cases were found to be 43 subject (7.76%; 6 females (1.08%); 37 males (6.68%)) and anti-IFN-alpha-2b positive cases were found to be 3 (0.54%; all males). Combined positivity against both IFN-alpha-1a and IFN-alpha-2b was 38 (6.86%; 7 females (1.26%) and 31 males (6.60%)). From these findings we can conclude that antibodies against IFN-alpha are present in considerable number at low titer in accepted blood donors.Cellular Immunology 08/2011; 271(2):365-70. · 1.97 Impact Factor