Combined use of the high heparin step and optical density to optimize diagnostic sensitivity and specificity of an anti-PF4/heparin enzyme-immunoassay.
Thromb Res
; 128(3): 256-60, 2011 Sep.
Article
em En
| MEDLINE
| ID: mdl-21620439
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.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.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.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.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.
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Base de dados:
MEDLINE
Assunto principal:
Trombocitopenia
/
Imunoglobulina G
/
Fator Plaquetário 4
/
Heparina
/
Técnicas Imunoenzimáticas
Tipo de estudo:
Diagnostic_studies
/
Prognostic_studies
Limite:
Humans
Idioma:
En
Ano de publicação:
2011
Tipo de documento:
Article