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Combined use of the high heparin step and optical density to optimize diagnostic sensitivity and specificity of an anti-PF4/heparin enzyme-immunoassay.
- Source :
-
Thrombosis research [Thromb Res] 2011 Sep; Vol. 128 (3), pp. 256-60. Date of Electronic Publication: 2011 May 28. - Publication Year :
- 2011
-
Abstract
- Background: IgG-specific anti-PF4/heparin enzyme-immunoassays (EIAs) are sensitive but not specific for platelet-activating antibodies, the cause of heparin-induced thrombocytopenia (HIT). Two features of EIA reactivity predict for presence of HIT antibodies - the magnitude of a positive result (in optical density [OD] units) and the inhibition of reactivity at high heparin concentrations - but their combined utility remains uncertain.<br />Objective: To determine for an IgG-specific EIA how the OD values of a positive reaction and its inhibition by high heparin can be optimally combined.<br />Methods: We screened 1,000 consecutive patients with suspected HIT using an IgG-specific PF4/heparin in-house EIA with and without high heparin (100 IU/mL); and by the heparin-induced platelet activation test.<br />Results: Platelet-activating antibodies were rarely detected (<0.2%) when the IgG-specific EIA was negative at the conventional cut-off (OD, 0.5). However, an OD cut-off of 1.0 resulted in an unacceptable loss of sensitivity (14/83=17%) for detecting platelet-activating antibodies. The high heparin step increased specificity for platelet-activating antibodies from 72% to 89% without loss of sensitivity when applied to weak-positive sera (OD≤1.0). However, decreased sensitivity was observed with strong-positive sera (OD>1.0): 11/69 such sera (16%) that did not show >40% inhibition by high heparin nevertheless contained platelet-activating antibodies.<br />Conclusion: Specificity of an IgG-specific EIA for detecting platelet-activating antibodies can be optimized by applying the high heparin inhibition step to weak-positive reactions (0.5-≤1.0 OD). However, applying the high heparin inhibition step to strong-positive reactions (>1.0 OD) in our in-house assay risks falsely classifying a serum as negative for platelet-activating antibodies.<br /> (Copyright © 2011 Elsevier Ltd. All rights reserved.)
- Subjects :
- Antibody Specificity
Densitometry methods
Heparin blood
Humans
Immunoenzyme Techniques standards
Immunoglobulin G immunology
Pilot Projects
Platelet Factor 4 blood
Sensitivity and Specificity
Thrombocytopenia blood
Thrombocytopenia immunology
Heparin immunology
Immunoenzyme Techniques methods
Immunoglobulin G blood
Platelet Factor 4 immunology
Thrombocytopenia diagnosis
Subjects
Details
- Language :
- English
- ISSN :
- 1879-2472
- Volume :
- 128
- Issue :
- 3
- Database :
- MEDLINE
- Journal :
- Thrombosis research
- Publication Type :
- Academic Journal
- Accession number :
- 21620439
- Full Text :
- https://doi.org/10.1016/j.thromres.2011.05.003