PB1098 - Results in Patients with Heparin Induced Thrombocytopenia or Vaccine Induced Thrombocytopenia with Thrombosis Confirm the Unsuitability of Using APTT Ratio to Monitor Argatroban Therapy

Tuesday, July 12, 2022

6:30 PM – 7:30 PM

Location: Exhibition

Presentation Format: In-Person

Presenting Author(s)

Sean Platton, MSc CSci FIBMS

Consultant Biomedical Scientist
Royal London Hospital Haemophilia Centre, Barts Health NHS Trust
London, England, United Kingdom

Co-Author(s)

CD

Chris Dale

Senior Specialist Biomedical Scientist
Haemostasis Laboratory, Royal London Hospital, Barts Health NHS Trust
London, England, United Kingdom
MD

Minal Dave

Haematology and Coagulation Operational Lead
Haemostasis Laboratory, Royal London Hospital, Barts Health NHS Trust
London, England, United Kingdom
NY

Nada Yartey

Senior Specialist Biomedical Scientist
Haemostasis Laboratory, Royal London Hospital, Barts Health NHS Trust
London, England, United Kingdom
Peter MacCallum, MD, FRCP, FRCPath

Consultant Haematologist
Department of Haematology, Royal London Hospital, Barts Health NHS Trust
London, England, United Kingdom

Background: The Summary of Product Characteristics for the direct thrombin inhibitor argatroban states monitoring should be by activated partial thromboplastin time (APTT), with a target range of 1.5-3.0 times the patient’s baseline APTT. APTT may be influenced by coagulopathies, lupus anticoagulant and raised FVIII levels.

Aims: We investigated the APTT ratio in patients receiving argatroban for the treatment of Vaccine Induced Thrombocytopenia with Thrombosis (VITT) in April and May 2021 and compared it to the APTT ratio for those being treated for Heparin Induced Thrombocytopenia (HIT) from June 2020 to May 2021.

Methods: 146 samples from 5 patients with VITT and 165 samples from patients with HIT were analysed on Sysmex CS-series analysers for APTT using Actin FS, and had argatrobran levels analysed using the Hyphen Biomed Hemoclot Thrombin Inhibitor reagents and Hyphen Biomed argatroban calibrators and controls.

Results: The APTT ratio was significantly shorter in VITT patients than in HIT patients, with a therapeutic level of argatroban (0.4–1.2 µg/mL) being equivalent to a median APTT ratio of 1.80 (95% confidence interval 1.31–2.60) in 106 HIT samples compared to 1.52 (1.07–2.86) in 67 VITT samples. An APTT ratio of 1.5–3.0 was equivalent to argatroban levels of 0.25–1.93 µg/mL in 125 HIT patients and 0.28–4.60 µg/mL in 82 VITT samples.

Conclusion(s): This study confirms the unsuitability of monitoring argatroban therapy by APTT ratio in either HIT or VITT.