Facing Deep Venous Thrombosis (DVT) in University Tertiary Hospital: Role of Conventional Thrombophilia Testing in Idiopathic DVT Treatment
Authors: Suito Milagros , Cerdá Maria , Benítez Olga , Cabirta Alba , Bosch Francesc , Santamaria Amparo 
Published: November 2019

INTRODUCTION: Deep venous thrombosis (DVT) is a frequent cause or morbidity and mortality, and multiple genetic and environmental factors are involved in its etiopathogenesis. According to it, besides investigating about personal and familiar DVT history, thrombophilia testing is often asked by physicians in order to diagnose patients, even if current validated markers can't predict the risk of recurrence of the disease.
METHODS: We developed an observational and prospective study between January 2017 and December 2017, in order to register the patients with DVT that were treated in our DVT unit. As secondary objectives, we wanted to know how many had an idiopathic DVT, if we tested all of them for thrombophilia, which of them stopped treatment and the results after one year of follow up.
RESULTS: We included 172 patients with DVT, 56.9% were men, and the average age was 66.4 years old with an increased incidence above the 50 years old. In our study group we found 43.6% (75) of patients without major risk factors for DVT, classified as idiopathic DVT and we will refer to them in this abstract from now on. Just 36.7% of them had a positive personal history of DVT and 36.7% had familiar history. Almost all were localized in the lower limbs (98.7%) and 17.3% presented in association with pulmonary embolism (PE) at diagnosis. All of them started treatment with LMWH, and after the first clinical visit, 26.7% continued with it, while 51.2% changed to VKA and 22.1% to DOACs. Only 45 (60%) of idiopathic DTVs were tested for thrombophilia (patients younger than 60 years old, with extensive DVT, or personal or familiar history of DVT): 31 had a negative study, 11 had a positive study for hereditary thrombophilia (4 S protein deficiency, 3 C protein deficiency, 2 V Leiden factor mutation + prothrombin mutation, 1 V Leiden factor mutation, 1 prothrombin mutation), and 3 were diagnosed of antiphospholipid syndrome. All these patients with positive study or antiphospholipid syndrome received indefinite anticoagulation. From all the patients with idiopathic DVT, 77.3% received indefinite anticoagulation, 17.3% were treated for 3-6 months, 4% for >6-12 months and 1,3% for 15 months. Only one patient who stopped treatment after 3 months had a recurrent DVT and had to restart it.
CONCLUSIONS: DVT is the most frequent indication for thrombophilia testing and regarding its multifactorial etiology, it must be performed specially in incidental cases. In our incidental DVT study group (with PE associated or not), we found a 31.1% of positive studies, consistent with what is expected in general DVT population, but in contrast with it is described in the literature, we found more cases of S and C deficiency than V Leiden factor and prothrombin mutations. We also had only one patient with recurrence DVT after few months of stopping anticoagulation, no thrombophilia was found. This low rate of recurrence that differs from the latest data published, might be explained by the short time of follow up that we have, so it would be interesting to increase it, as well as the number of patients in the cohort studied. There is a need for investigating new clinical and genetic scores in order to improve the poor predictive role in recurrent disease with the current thrombophilia markers.

Disclosures
Bosch: F. Hoffmann-La Roche Ltd/Genentech, Inc.: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Takeda: Honoraria, Research Funding; AstraZeneca: Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Honoraria, Research Funding; Acerta: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Kyte: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau.