PB1357 - Addition of platelet factor 4 in the heparin-induced platelet activation (HIPA) test for the diagnosis of Heparin Induced Thrombocytopenia (HIT) : results from a restrospective monocentric study

Tuesday, June 27, 2023

18:30 – 19:30 ET

Room: Exhibition

Co-Author(s)

FP

Fanny PEREZ

Intern
Bichat Hospital, Paris, France
PARIS, Ile-de-France, France
Marie-Charlotte BOURRIENNE, PharmD (she/her/hers)

Assistant
Laboratoire d'Hématologie, AP-HP, Hôpital Bichat Claude-Bernard, Paris, France.
PARIS, Ile-de-France, France
YB

Yaël BAUDOUIN

Technician
Bichat Hospital, Paris, France
PARIS, Ile-de-France, France
CC

Cécile CLEMENT

Technician
Bichat Hospital, Paris, France
PARIS, Ile-de-France, France
IF

Inès FERREIRA

Technician
Bichat Hospital, Paris, France
PARIS, Ile-de-France, France
LU

Laureen URRUTY

Technician
Bichat Hospital, Paris, France
PARIS, Ile-de-France, France
AP

Andreas PERRIER-CORNET

Hospital practitioner
Bichat Hospital, Paris, France
PARIS, Ile-de-France, France
JG

Juliette GAY

Assistant
Bichat Hospital, Paris, France
PARIS, Ile-de-France, France
NA

Nadine Ajzenberg

MD, PhD
Laboratoire d'Hématologie, AP-HP, Hôpital Bichat Claude-Bernard, Paris, France.
Paris, Ile-de-France, France

Presenting Author(s)

Dorothée FAILLE, PharmD, PhD (she/her/hers)

Associate professor
1. Université Paris Cité, INSERM, U1148 LVTS, F-75018 Paris. 2. Laboratoire d'Hématologie, AP-HP, Hôpital Bichat Claude-Bernard, F-75018 Paris.
PARIS CEDEX 18, Ile-de-France, France

Background: Heparin-induced thrombocytopenia (HIT) is a rare but severe complication of heparin therapy. Its biological diagnosis relies on functional tests detecting pathogenic anti-PF4/heparin antibodies able to activate platelets in the presence of heparin. Functional tests using washed platelets, including Heparin-Induced Platelet Activation Assay (HIPA), have a good specificity (>99%). The addition of exogenous PF4 in washed platelet suspension may improve its ability to detect low levels of pathogenic HIT antibodies and thus increase their sensitivity.

Aims: 1/To determine whether PF4 supplementation increases HIPA sensitivity 2/To better characterize patients for whom PF4 addition would be beneficial

Methods: HIPA results from patients with a clinical suspicion of HIT and positive anti-PF4/heparin antibodies (Zymutest HIA IgG) were reviewed restrospectively. HIPA was performed with or without 10μg/ml recombinant human PF4 to the reaction mixture containing 0.2 or 50UI/mL unfractionated heparin.

Results: Between 2019 and 2021, 131 patients, including 59 (45%) post cardiac surgery, were included. Considering that patient plasma were tested on ≥2 platelet donors, results from 546 conditions with or without PF4 could be compared. Among 265 negative HIPA results, 30 (11.3%) became positive after PF4 addition (table 1). Regarding global HIT conclusion, among 48 patients for whom HIT could not be confirmed by conventional HIPA, PF4 supplementation enabled to reconsider HIT diagnosis as positive in 5 (10.4%) patients (table 2), including 3 (60%) cardiac surgery patients. Importantly, those patients had significantly lower anti-PF4/heparin antibody plasma levels than patients positive with the conventional HIPA (mean OD 1536±317 vs 2174±562, p=0.02). Conversely, 29/257 positive HIPA results became negative which could have lead to missclassify 3/68 HIT positive patients as negative if only the HIPA with PF4 was considered.

Conclusion(s): Exogenous PF4 should not be added systematically in the HIPA test but should be restricted to patients with intermediate anti-PF4/heparin IgG levels, strong clinical HIT suspicion but negative conventional HIPA.