title: Timely diagnosis and management of heparin-induced thrombocytopenia in a frequent request, low incidence single centre using clinical 4T's score and particle gel immunoassay.
abstract: Clinicians must promptly decide which patients suspected of having heparin-induced thrombocytopenia (HIT) warrant a change in anticoagulation. This single-centre series of 246 HIT testing referrals assessed the combination of clinical score (thrombocytopenia, timing, thrombosis, other causes of thrombocytopenia not evident; 4T's), Diamed ID-Heparin-PF4 immunoassay (PaGIA) and 14C Serotonin Release Assay (SRA) to develop a practical and safe diagnostic strategy for HIT. A total of 142/256 (58%) referrals were in patients with a low 4T's score, with 12/246 (5%) in the high scoring group. PaGIA was positive in 24/246 (9.7%) patients, whilst SRA was positive in 9/246 (3.6%). The overall positive predictive value of a positive PaGIA test alone was 37.5%, however this reached 80% for the high scoring group. Both negative PaGIA and low clinical score independently had negative predictive values of 100%. We subsequently developed an algorithm that, when applied to this cohort, would have resulted in 18/246 patients (7%) definitely requiring alternative anticoagulation, whilst a further 7/246 (2.8%) patients would have been considered on an individual basis. Ultimately (based on SRA) this would have resulted in 16/246 (6.5%) patients unnecessarily having a change in their anticoagulation, with 9/246 (3.6%) patients being 'correctly treated'. The combination of 4T's scoring and PaGIA permitted a practical and safe approach to rapid HIT diagnosis and management.
authors.affiliation: Department of Haematology, St Vincent's Hospital, Sydney, NSW, Australia.
authors.forename: Adam
authors.initials: A
authors.lastname: Bryant
authors.forename: Joyce
authors.initials: J
authors.lastname: Low
authors.forename: Steven
authors.initials: S
authors.lastname: Austin
authors.forename: Joanne E
authors.initials: JE
authors.lastname: Joseph
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D000925:Anticoagulants / Q000009:adverse effects*; D001323:Autoantibodies / Q000097:blood; D001792:Blood Platelets / Q000378:metabolism; D005260:Female; D006495:Heparin, Low-Molecular-Weight / Q000009:adverse effects*; D006801:Humans; D007118:Immunoassay / Q000379:methods; D008297:Male; D008875:Middle Aged; D010976:Platelet Count; D010978:Platelet Factor 4 / Q000276:immunology; D012701:Serotonin / Q000378:metabolism; D013921:Thrombocytopenia / Q000139:chemically induced* / Q000175:diagnosis* / Q000188:drug therapy; D013927:Thrombosis / Q000097:blood / Q000188:drug therapy / Q000276:immunology; D055815:Young Adult
chemical_list: D000925:Anticoagulants; D001323:Autoantibodies; D006495:Heparin, Low-Molecular-Weight; D012701:Serotonin; D010978:Platelet Factor 4