VPB0128 - Characteristics of Critically Ill COVID-19 Patients with Positive Heparin-Induced Thrombocytopenia Antibody

Background: COVID-19 triggers a potentially fatal hypercoagulable state. Multiple mechanisms may contribute to this disorder, among which the production of abnormal antibodies, especially Heparin-induced thrombocytopenia (HIT) antibodies. There have been a few single case reports about HIT in COVID-19 patients. Nevertheless, risk factors for HIT in COVID-19 patients are still under investigation.

Aims: We present a case series of critically ill COVID-19 patients with positive HIT antibodies treated at Cho Ray Hospital from July 2021 to December 2021.

Methods: This is a retrospective case series report of critically ill COVID-19 patients who were tested positive for HIT antibodies using an Anti-PF4/Heparin antibody chemiluminescent assay with a cut-off value of 1.0 U/ml. Demographic information, clinical and laboratory characteristics were described.

Results: 17 patients (9 female, 8 male) were included in the case series. Mean age was 59.24 ± 12.95. Mean heparin exposure duration was 13.94 ± 8.26 days for all types and 10.88 ± 7.15 days for unfractionated heparin. Mean HIT antibody titer was 2.45 ± 1.91 U/ml. 2/17 patients were also tested positive for antiphospholipid antibodies. Baseline platelet count was 235.82 ± 76.42 x 10e9/L. Nadir platelet count was 63.35 ± 51.58 x 10e9/L. Baseline D-dimer was 6813.47 ± 15028.00 ng/ml. Peak D-dimer was 14839.71 ± 16436.64 ng/ml. Only 2/17 patients had proven thrombosis. 10/17 patients had secondary infections, most notably with Acinetobacter baumanii (6/17) and Klebsiella pneumoniae (5/17.) 16/17 patients perished in-hospital.

Conclusion(s): From our case series, we suspect that beside long, continuous exposure to heparin, secondary bacterial infections can be an important risk factor for HIT in COVID-19 patients. Furthermore, co-positivity with antiphospholipid antibodies may occur and complicate treatment options. Lastly, critically ill COVID-19 patients with positive HIT antibody seemed to have a very poor survival rate. However, whether this phenomenon is related to HIT remains to be investigated in future studies.