Combination of 4Ts score and PF4/H-PaGIA for diagnosis and management of heparin-induced thrombocytopenia: prospective cohort study.
Rapid exclusion of heparin-induced thrombocytopenia (HIT) is needed to determine which patients can continue to receive heparin. In this prospective management study, 526 participants had a 4Ts score, rapid particle gel immunoassay (platelet factor 4/heparin [PF4/H]-PaGIA), and serotonin-release assay (SRA) performed. While awaiting SRA results, participants with a low 4Ts score (irrespective of PF4/H-PaGIA result) or intermediate 4Ts score plus a negative PF4/H-PaGIA result received prophylactic doses of danaparoid or fondaparinux; all others received therapeutic doses of nonheparin anticoagulants. The primary outcome was the frequency of management failures defined as HIT-positive participants with a low 4Ts score (irrespective of PF4/H-PaGIA result) or intermediate 4Ts score plus negative PF4/H-PaGIA result. Six participants (1.1%; 95% confidence interval [CI], 0.2-2.1%) were management failures. A negative PF4/H-PaGIA result reduced the pretest probability of HIT from 1.9% to 0% (95% CI, 0-1.3%), 6.7% to 0% (95% CI, 0-2.7%), and 36.6% to 0% (95% CI, 0-14.3%) in the low, intermediate, and high score groups, respectively. A positive PF4/H-PaGIA result increased the probability of HIT in the low score group to 15.4% (95% CI, 5.9-30.5). Thus, a low or intermediate 4Ts score plus negative PaGIA result excluded HIT, whereas any other combination of results justified the use of alternative anticoagulants until HIT could be excluded. This trial was registered at www.clinicaltrials.gov as #NCT00489437.
Department of Medicine, McMaster University, Hamilton, ON, Canada; Thrombosis & Atherosclerosis Research Institute, Hamilton, ON, Canada;
Lori-Ann
LA
Linkins
Department of Medicine, McMaster University, Hamilton, ON, Canada; Thrombosis & Atherosclerosis Research Institute, Hamilton, ON, Canada;
Shannon M
SM
Bates
Division of Hematology, University of British Columbia, Vancouver, BC, Canada; and.
Agnes Y Y
AY
Lee
Department of Medicine, McMaster University, Hamilton, ON, Canada;
Nancy M
NM
Heddle
Department of Medicine, McMaster University, Hamilton, ON, Canada;
Grace
G
Wang
Department of Pathology and Molecular Medicine, Michael G. DeGroote School of Medicine, McMaster University, Hamilton, ON, Canada.
Theodore E
TE
Warkentin
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D000925:Anticoagulants / Q000009:adverse effects / Q000276:immunology / Q000627:therapeutic use; D015331:Cohort Studies; D005260:Female; D006493:Heparin / Q000009:adverse effects* / Q000276:immunology; D006801:Humans; D007118:Immunoassay / Q000379:methods; D007074:Immunoglobulin G / Q000097:blood; D008297:Male; D008875:Middle Aged; D010978:Platelet Factor 4 / Q000276:immunology; D011446:Prospective Studies; D012701:Serotonin / Q000378:metabolism; D013921:Thrombocytopenia / Q000139:chemically induced* / Q000175:diagnosis* / Q000628:therapy; D016896:Treatment Outcome
D000925:Anticoagulants; D007074:Immunoglobulin G; D012701:Serotonin; D010978:Platelet Factor 4; D006493:Heparin