title: Plasma exchange to remove HIT antibodies: dissociation between enzyme-immunoassay and platelet activation test reactivities.
abstract: Repeated therapeutic plasma exchange (TPE) has been advocated to remove heparin-induced thrombocytopenia (HIT) IgG antibodies before cardiac/vascular surgery in patients who have serologically-confirmed acute or subacute HIT; for this situation, a negative platelet activation assay (eg, platelet serotonin-release assay [SRA]) has been recommended as the target serological end point to permit safe surgery. We compared reactivities in the SRA and an anti-PF4/heparin IgG-specific enzyme immunoassay (EIA), testing serial serum samples in a patient with recent (subacute) HIT who underwent serial TPE precardiac surgery, as well as for 15 other serially-diluted HIT sera. We observed that post-TPE/diluted HIT sera-when first testing SRA-negative-continue to test strongly positive by EIA-IgG. This dissociation between the platelet activation assay and a PF4-dependent immunoassay for HIT antibodies indicates that patients with subacute HIT undergoing repeated TPE before heparin reexposure should be tested by serial platelet activation assays even when their EIAs remain strongly positive.
authors.affiliation: Department of Pathology and Molecular Medicine, Department of Medicine, and.
authors.forename: Theodore E
authors.initials: TE
authors.lastname: Warkentin
authors.affiliation: Department of Pathology and Molecular Medicine.
authors.forename: Jo-Ann I
authors.initials: JA
authors.lastname: Sheppard
authors.affiliation: Department of Surgery, McMaster University, Hamilton, ON, Canada.
authors.forename: F Victor
authors.initials: FV
authors.lastname: Chu
authors.affiliation: Department of Surgery, McMaster University, Hamilton, ON, Canada.
authors.forename: Anil
authors.initials: A
authors.lastname: Kapoor
authors.affiliation: Department of Pathology and Molecular Medicine, Department of Medicine, and.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Crowther
authors.affiliation: Department of Medicine, and.
authors.forename: Azim
authors.initials: A
authors.lastname: Gangji
mesh_terms: D000368:Aged; D001792:Blood Platelets / Q000378:metabolism*; D002277:Carcinoma / Q000150:complications; D005260:Female; D006470:Hemorrhage; D006493:Heparin / Q000009:adverse effects*; D006801:Humans; D007124:Immunoenzyme Techniques / Q000379:methods*; D007074:Immunoglobulin G / Q000737:chemistry; D007680:Kidney Neoplasms / Q000150:complications; D010951:Plasma Exchange / Q000379:methods*; D015539:Platelet Activation / Q000187:drug effects; D010978:Platelet Factor 4 / Q000378:metabolism; D013921:Thrombocytopenia / Q000139:chemically induced*; D013927:Thrombosis / Q000628:therapy; D016896:Treatment Outcome; D014682:Vena Cava, Inferior / Q000473:pathology
chemical_list: D007074:Immunoglobulin G; D010978:Platelet Factor 4; D006493:Heparin