title: A Novel PF4-Dependent Platelet Activation Assay Identifies Patients Likely to Have Heparin-Induced Thrombocytopenia/Thrombosis.
abstract: Almost without exception, patients with heparin-induced thrombocytopenia/thrombosis (HIT) have antibodies that recognize platelet factor 4 (PF4) in a complex with heparin; however, many heparin-treated patients without HIT are also antibody-positive. A platelet activation test, the serotonin release assay (SRA), is useful for identifying a subset of antibodies that are platelet-activating and most likely to cause HIT. However, this "gold standard" assay for HIT diagnosis is technically demanding and is routinely available only through referral laboratories, limiting its availability for timely diagnosis and management.
  
  
  
  We compared the diagnostic performance of the SRA with that of a technically simple platelet activation assay, the PF4-dependent P-selectin expression assay (PEA), which uses platelets pretreated with PF4 as targets for antibody detection. Archived serum samples from 91 patients for whom clinical information (HIT 4Ts [thrombocytopenia, timing of platelet count fall, thrombosis, and other causes of thrombocytopenia] score) was available were used. Patients with an intermediate 4Ts score and a PF4 ELISA (enzyme-linked immunosorbent assay) optical density ≥ 2.0, or a high 4Ts score and a PF4 ELISA optical density ≥ 1.0, were considered HIT positive; others were designated HIT negative.
  
  
  
  The PEA had higher diagnostic accuracy (area under the curve, 0.92 vs 0.82; P = .02) than the SRA, using this definition of HIT. Eleven of 16 serum samples that were PEA positive and SRA negative were HIT positive. Studies done with identical target platelets and serially diluted samples from patients with HIT showed that the PEA is inherently more sensitive than the SRA for the detection of platelet-activating antibodies.
  
  
  
  The PEA is technically less demanding than the SRA and may be more accurate for the diagnosis of HIT.
authors.affiliation: Medical Sciences Institute, BloodCenter of Wisconsin, Milwaukee, WI; Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, WI; Department of Pathology, Medical College of Wisconsin, Milwaukee, WI. Electronic address: anand.padmanabhan@bcw.edu.
authors.forename: Anand
authors.initials: A
authors.lastname: Padmanabhan
authors.affiliation: Medical Sciences Institute, BloodCenter of Wisconsin, Milwaukee, WI.
authors.forename: Curtis G
authors.initials: CG
authors.lastname: Jones
authors.affiliation: Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, WI; Platelet and Neutrophil Immunology Laboratory, BloodCenter of Wisconsin, Milwaukee, WI.
authors.forename: Brian R
authors.initials: BR
authors.lastname: Curtis
authors.affiliation: Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, WI.
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Bougie
authors.affiliation: Platelet and Neutrophil Immunology Laboratory, BloodCenter of Wisconsin, Milwaukee, WI.
authors.forename: Mia J
authors.initials: MJ
authors.lastname: Sullivan
authors.affiliation: Department of Medicine, Medical College of Wisconsin, Milwaukee, WI.
authors.forename: Namrata
authors.initials: N
authors.lastname: Peswani
authors.affiliation: Platelet and Neutrophil Immunology Laboratory, BloodCenter of Wisconsin, Milwaukee, WI; Department of Medicine, Medical College of Wisconsin, Milwaukee, WI.
authors.forename: Janice G
authors.initials: JG
authors.lastname: McFarland
authors.affiliation: Department of Biostatistics, Medical College of Wisconsin, Milwaukee, WI.
authors.forename: Daniel
authors.initials: D
authors.lastname: Eastwood
authors.affiliation: Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, WI; Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, WI.
authors.forename: Demin
authors.initials: D
authors.lastname: Wang
authors.affiliation: Blood Research Institute, BloodCenter of Wisconsin, Milwaukee, WI; Department of Medicine, Medical College of Wisconsin, Milwaukee, WI.
authors.forename: Richard H
authors.initials: RH
authors.lastname: Aster
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000009:adverse effects*; D001323:Autoantibodies / Q000276:immunology; D016022:Case-Control Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006493:Heparin / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D019007:P-Selectin / Q000378:metabolism; D015539:Platelet Activation; D010978:Platelet Factor 4 / Q000276:immunology; D013921:Thrombocytopenia / Q000139:chemically induced* / Q000175:diagnosis / Q000276:immunology; D013927:Thrombosis / Q000139:chemically induced* / Q000175:diagnosis / Q000276:immunology
chemical_list: D000925:Anticoagulants; D001323:Autoantibodies; D019007:P-Selectin; C546937:SELP protein, human; D010978:Platelet Factor 4; D006493:Heparin
keywords: heparin; thrombocytopenia; thrombosis