PO0012 - A frequency of anti-PF4/heparin antibodies and LA in patients with COVID-19

Background: As COVID-19 is associated with a prothrombotic condition and some critically ill patients may even undergo extracorporeal oxygenation treatment, heparin is the essential for treatment in these situations. The prevalence of anti-platelet factor 4 (PF4)/heparin antibodies associated with thrombotic tendency may be present in patients hospitalized for COVID-19 without heparin therapy. Lupus anticoagulant (LA) included in the diagnostic criteria for antiphospholipid syndrome, which is one of the common causes of thrombophilia, is also commonly detected during SARS-CoV-2 infection. Most patients hospitalized for COVID-19 showed elevated D-dimer and prolonged activated partial thromboplastin time (aPTT), However, there were no studies on the association of SARS-CoV-2 infection with LA and anti-PF4/heparin antibodies.

Aims: The purpose of this study was to analyze the expression of LA and anti-PF4/heparin antibodies associated with thrombotic tendency in COVID-19 patients.

Methods: We performed LA test (Instrumentation Laboratory, Bedford, MA) and LIFECODES PF4 IgG assay (Immucor, Norcross, GA) on 46 COVID-19 patients admitted to Asan Medical Center and analyzed their frequency.

Results: Of a total of 46 COVID-19 patients, 26 patients (56.5%) were positive for LA test, 3 patients (6.5%) for anti-PF4/heparin antibodies. In particular, anti-PF4/heparin antibodies was detected only in LA-negative patients and showed low optical density values (3 out of 20 LA-negative patients, 15.0%). All three patients positive for anti-PF4/heparin antibodies had no history of heparin treatment.

Conclusion(s): In COVID- 19- patients, anti- PF4/heparin antibody test does not predict clinically relevant HIT antibodies. Anti-PF4/heparin antibodies appear in LA-negative COVID-19 patients, so they are carefully expected to serve as LA-independent indicators.