title: Serological investigation of patients with a previous history of heparin-induced thrombocytopenia who are reexposed to heparin.
abstract: Heparin reexposure despite a history of previous heparin-induced thrombocytopenia (HIT) can be appropriate if platelet-activating antibodies are no longer detectable. We determined the frequency, timing, and magnitude of the antiplatelet factor 4 (anti-PF4)/heparin immune response (by serotonin-release assay [SRA] and enzyme-immunoassay [EIA]), and the frequency of recurrent HIT in 20 patients with previous HIT reexposed to heparin 4.4 years (mean) post-HIT; 17 patients were given heparin intraoperatively (without postoperative heparin) for cardiac/vascular surgery. One patient developed recurrent HIT beginning 7 days after cardiac surgery, with newly regenerated HIT antibodies exhibiting strong heparin-independent platelet-activating properties. Intraoperative heparin induced EIA seroconversion in 11/17 (65%) patients (immunoglobulin G [IgG]>IgA>IgM) and SRA seroconversion in 8/17 (47%), whereas none of 3 medical patients reexposed to heparin developed seroconversion. Anti-PF4/heparin IgG became detectable at day 7 (median), ie, no sooner than observed in typical-onset HIT. The high proportion of SRA positivity among EIA-seroconverting patients (8/11 [73%]) suggests that patients with previous HIT may be especially predisposed to forming recurrent antibodies with platelet-activating properties. We conclude that among patients with a previous history of HIT who are reexposed to intraoperative (but not postoperative) heparin, the risk of recurrent HIT appears to be low, but is possible if antibodies with strong heparin-independent platelet-activating properties are formed.
authors: Department of Pathology and Molecular Medicine and.
authors: Theodore E
authors: TE
authors: Warkentin
authors: Jo-Ann I
authors: JA
authors: Sheppard
mesh_terms: D000368:Aged; D006348:Cardiac Surgical Procedures; D018890:Chemoprevention; D005260:Female; D006493:Heparin / Q000008:administration & dosage / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012008:Recurrence; D019233:Retreatment; D012189:Retrospective Studies; D012698:Serologic Tests; D013921:Thrombocytopenia / Q000175:diagnosis* / Q000209:etiology / Q000276:immunology; D013927:Thrombosis / Q000517:prevention & control*
chemical_list: D006493:Heparin