PB0144 - Use of an FVIIa antithrombin activity assay to determine the incidence of antithrombin deficiency in a high-risk population.

Background: A newly identified genetic variant that causes functional antithrombin deficiency associated with a prothrombotic tendency has been reported. This variant, resulting in an altered glycosylation profile of antithrombin cannot be identified using routinely employed FXa or FIIa based antithrombin activity (AT:Act) assays , however it has been demonstrated that a FVIIa based AT:Act would identify this type of antithrombin deficiency.

Aims: Local practice is to perform inherited thrombophilia testing in those with an unprovoked venous thromboembolic event and a strong family history. The aim of this study is to validate a FVIIa based AT:Act assay and utilise it alongside FXa and FIIa based AT:Act methods in local inherited thrombophilia testing. Information obtained will be assessed regarding prevalence of this antithrombin deficiency in a UK population.

Methods: Requests received for inherited thrombophilia testing will be assayed for AT:Act by three methods; FIIa based (Berichrom® Antithrombin III (A), Siemens, Germany) and FXa based (BIOPHEN™ AT anti-(h)-Xa LRT, HYPHEN BioMed, France) AT:Act using a CN series coagulometer (Sysmex, Japan) and FVIIa based (Asserachrom® VIIa-AT, Stago, France) AT:Act using a Dynex DS2 automated ELISA analyser (Werfen, US). Patients identified with reduced AT:Act by any method will be clinically reviewed and referred for genetic testing.

Results: An interim review of data from the use of three AT:Act methodologies will be reported, half way through this one year study.

Conclusion(s): We will present interim results of rates of antithrombin deficiency using multiple methods of AT:Act testing in those with an unprovoked venous thromboembolic event and a family history at the conference.