scholarly journals Acquired and Inherited Thrombophilia Testing in Patients with Chronic Thromboembolic Pulmonary Hypertension: Value of Testing in an Academic Health Center

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 4256-4256
Author(s):  
Bharath Ram S ◽  
Monisha Harimadhavan ◽  
Shilpa Prabhu ◽  
Karthick R G ◽  
Devi Prasad Shetty ◽  
...  
Keyword(s):  
Pulmonary Hypertension ◽  
Protein C ◽  
Chronic Thromboembolic Pulmonary Hypertension ◽  
Factor V Leiden ◽  
Anticardiolipin Antibody ◽  
Mthfr Gene ◽  
Factor V ◽  
Inherited Thrombophilia ◽  
Glycoprotein I ◽  
Thrombophilia Testing

Abstract Introduction Chronic thromboembolic pulmonary hypertension (CTEPH) is classed as group 4 in the present classification of pulmonary hypertension. The pathophysiology of CTEPH is complex, mainly is a consequence of prior acute pulmonary embolism with failure of thrombi to resolve and the recent recognition of added small vessel changes which impacts long-term outcomes even after surgical management. The role of thrombophilia testing in this condition has been debated. Hence, we here analyzed the utility of thrombophilia testing in CTEPH from a center in a developing country. Methods This is a single institution (Narayana Health City, Bangalore); retrospective study including patients ≥ 18 years of age who underwent thrombophilia workup in a diagnosis of CTEPH from January 2019 till July 2021. Tests done to evaluate thrombophilia included factor V Leiden; prothrombin F20210A mutation; MTHFR gene mutation; Protein C, S, and antithrombin deficiency; lupus anticoagulant, anti-beta2 glycoprotein I (IgM and IgG) and anticardiolipin antibody (IgM and IgG); hyperhomocysteinemia and anti-nuclear antibody testing (ANA-IF). The study was approved by the ethics committee of the institute and was carried out in accordance with the principles of the declaration of Helsinki. Results and discussion The study included 56 patients with a median age of 37 years (range 23-50), and 36 (64%) were males. Patients with recurrent venous thrombosis included 37 (66%), with the majority having thrombosis at 2 sites (53%; 22 patients with associated deep vein thrombosis). A family history of thrombosis was present in 4 patients. The majority of patients received vitamin K antagonists (76%), with the rest receiving direct oral anticoagulants (DOAC). Among the tests sent for acquired thrombophilia, ANA-IF and antiphospholipid antibody (APLA) were most frequently evaluated (94%). ANA-IF and APLA tests were positive in 5.6% and 30.1%, respectively. Among the APLA tests, Anti-beta2 glycoprotein I (IgM or IgG) was the most commonly detected antibody (13/46), followed by anticardiolipin antibody (IgG or IgM) (9/43) and lupus anticoagulant (7/40). Double and triple positive APLA were present in 3 and 4 patients, respectively. Homocysteine levels were high in 93.7% though only 16 patients were tested in this cohort. Among the tests for inherited thrombophilia, genetic tests (factor V Leiden, prothrombin F20210A mutation, and MTHFR gene mutation) were tested in only ~50%. Twenty-three percent were positive for heterozygous MTHFR followed by MTHFR compound heterozygous (10%) and heterozygous factor V Leiden heterozygous (10%). Antithrombin III, protein C, and S were tested in ~30% of patients. Antithrombin III was low in only 1 patient, with protein C and S assays being normal in all the patients. The cost analysis was calculated, showed a median of $364 (₹ 27,055) was spent per person on thrombophilia workup. The median cost incurred per patient for inherited thrombophilia workup was $232 (₹ 17,300) and for acquired thrombophilia was $132 (₹ 9814), respectively. Conclusion This single-institution study on thrombophilia workup in CTEPH patients reveals that APLA was the most commonly performed test with high positivity rates of 30.1%. Among the inherited thrombophilia, the positivity rate of MTHFR mutation was highest (33.3%), with other tests having a low positivity rate (0-10%). Hence, we would recommend APLA testing in all patients with CTEPH considering its high positivity and clinical utility. Testing for other thrombophilias should be pursued judiciously especially in economically restrictive settings. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Fundamentals and Patient Evaluation

2006 ◽  
Author(s):  
Richard C. Becker ◽  
Frederick A. Spencer
Keyword(s):  
General Population ◽  
Venous Thrombosis ◽  
Protein C ◽  
Factor V Leiden ◽  
Protein S ◽  
Incidence Rates ◽  
Factor V ◽  
Inherited Thrombophilia ◽  
Occult Malignancy ◽  
History Of

Thrombophilia is the term used to describe a tendency toward developing thrombosis. This tendency may be inherited, involving polymorphism in gene coding for platelet or clotting factor proteins, or acquired due to alterations in the constituents of blood and/or blood vessels. An inherited thrombophilia is likely if there is a history of repeated episodes of thrombosis or a family history of thromboembolism. One should also consider an inherited thrombophilia when there are no obvious predisposing factors for thrombosis or when clots occur in a patient under the age of 45. Repeated episodes of thromboembolism occurring in patients over the age of 45 raise suspicion for an occult malignancy. A summary of inherited thrombophilias are summarized in Table 24.1. This list continues to grow, as new genetic polymorphisms and combined mutations are being detected. The prevalence of common thrombophilias is shown in Figure 24.1. Factor V Leiden (FVL) mutation and hyperhomocysteinemia are present in nearly 5% of the general population and are often found in patients with venous thrombosis, while deficiencies of antithrombin (AT), protein C, and protein S are relatively uncommon. Elevated levels of factor VIII (FVIII) are uncovered frequently in the general population and in patients with thrombosis. This is not surprising as FVIII is an acute-phase reactant that increases rapidly after surgery or trauma; however, prospective studies have shown that FVIII elevation in some patients cannot be attributed to a stress reaction and probably represents mutations in the genes regulating FVIII synthesis or release (Kyrle et al., 2000). The same may be true for factors IX and XI. The relative risks for thrombosis among patients with inherited thrombophilias have been determined. While AT mutations are the least common, they are associated with a substantial risk of venous thrombosis; similar risk is seen with protein C and S deficiency. In contrast, the lifetime risk of having a thromboembolic event in an individual heterozygous for FVL is comparatively low (Martinelli et al., 1998). Incidence rates markedly increase with age, and are highest among those with AT deficiency, followed by protein C and protein S, and least with FVL.

scholarly journals Utility of current thrombophilia screening in young patients with stroke and TIA

2018 ◽  
Vol 3 (4) ◽  
pp. 231-236 ◽  
Author(s):  
Vafa Alakbarzade ◽  
Alice Taylor ◽  
Marie Scully ◽  
Robert Simister ◽  
Arvind Chandratheva
Keyword(s):  
Protein C ◽  
Young Patients ◽  
Factor V Leiden ◽  
Anticardiolipin Antibody ◽  
Antiphospholipid Antibody ◽  
G20210a Mutation ◽  
Thrombophilia Screening ◽  
Thrombophilia Testing ◽  
Clinical Records ◽  
The Impact

IntroductionApproximately 40% of strokes in young adults are cryptogenic. The diagnostic yield of thrombophilia screening remains controversial. We aimed to determine utility of current thrombophilia testing for young patients with stroke and transient ischaemic attack (TIA).MethodsWe present a retrospective review of all patients with stroke and TIA ≤60 years presenting to University College London Hospital stroke unit and daily TIA clinic from 1 January 2015 to 1 August 2016. Consecutive clinical records and thrombophilia tests, including factor V Leiden (FVL), prothrombin G20210A mutation (PGM), antiphospholipid antibody (APA), and protein S, C and antithrombin (AT) levels, were reviewed.ResultsThe mean age of 628 patients with stroke and TIA was 49.1 years (SD 9.2). Thrombophilia testing was performed in 360 (57%) patients, including 171 with stroke and 189 with TIA. Positive tests were found in 50 (14%) patients, of whom 24 patients were <50 years. Positive results were found in 36 (10%) with acute ischaemic stroke, 4 (1%) with haemorrhagic stroke and 10 (3%) with TIA. Thirteen patients (4%) had homozygous/heterozygous FVL or PGM, and 27 (7.5%) had positive APA (anticardiolipin antibody, anti-β2 glycoprotein antibody or lupus anticoagulant). Of 27 (7.5%) patients with protein C, S or AT deficiency, 10 (2.8%) had primary deficiency, presumed hereditary with other secondary causes excluded. 9% of patients with protein C, S or AT and 27% with APA were followed by confirmatory testing.ConclusionThrombophilia testing was positive in only 14% of cases overall. Thrombophilia mutations and protein C, S or AT abnormalities were found rarely and were very uncommon in patients with TIA. Follow-up of abnormal results was generally poor for all groups, which further limited the impact of the thrombophilia testing policy.

scholarly journals Heritable Thrombophilia in Venous Thromboembolism in Northern Pakistan: A Cross-Sectional Study

2021 ◽  
Vol 2021 ◽  
pp. 1-5
Author(s):  
Maria Khan ◽  
Chaudhry Altaf ◽  
Hamid Saeed Malik ◽  
Muhammad Abdul Naeem ◽  
Aamna Latif
Keyword(s):  
Venous Thromboembolism ◽  
Protein C ◽  
Gene Mutations ◽  
Factor V Leiden ◽  
Factor V ◽  
Protein C Deficiency ◽  
Factor V Leiden Mutation ◽  
Inherited Thrombophilia ◽  
At Deficiency ◽  
Prothrombin Gene

Background. Venous thromboembolism (VTE) is referred to as formation of clots in a deep vein or lodging of thrombus towards the lungs which could be fatal yet preventable. The risk of developing VTE can be increased by various factors. Where there are innumerable acquired causes, the possibility of inherited thrombophilia cannot be ignored. In view of this, we have evaluated all patients with venous thromboembolism for inherited thrombophilia. Objective. To evaluate the frequencies of antithrombin (AT) deficiency, protein C and S deficiencies, Factor V Leiden, and prothrombin gene mutations in patients harboring venous thromboembolism. Materials and Methods. A study comprising of 880 patients who were presented with manifestations of venous thromboembolism was conducted from July 2016 to June 2017. A blood sample collected from patients was screened for thrombophilia defects encompassing AT, protein C and S deficiencies, Factor V Leiden, and prothrombin gene mutations. All acquired causes of thrombosis were excluded. Results. Of 880 patients who underwent screening for thrombophilia, 182 patients demonstrated VTE history. Their age ranged from 1 to 58 years. Males constituted a predominant group. About 45 (24.7%) patients had evidence of heritable thrombophilia. Of these, 20 (10.9%) had AT deficiency, 9 (4.9%) had Factor V Leiden mutation, 6 (3.2%) had protein C deficiency, whereas protein S deficiency and prothrombin gene mutation both were found in 5 (2.7%) patients. Conclusion. Our study illustrated the highest frequency of antithrombin deficiency among other investigated thrombophilia defects.

scholarly journals Evaluation of Direct Oral Anticoagulants in the Treatment of Venous Thromboembolism for Inherited Thrombophilia Disorders

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 5007-5007 ◽  
Author(s):  
Ali McBride ◽  
Reem Diri ◽  
Ravitharan Krishnadasan ◽  
Pavani Chalasani ◽  
Ivo Abraham ◽  
...  
Keyword(s):  
Risk Factors ◽  
Venous Thromboembolism ◽  
Protein C ◽  
Factor V Leiden ◽  
Secondary Prophylaxis ◽  
Factor V ◽  
Inherited Thrombophilia ◽  
Dvt Prophylaxis ◽  
Prothrombin Gene ◽  
Baseline Characteristics

Abstract Background Venous thromboembolism can be classified according to the presence of either environmental or genetic risk factors. Risk factors for thrombosis can include activated protein C resistance, and heritable including deficiencies of antithrombin, protein C or protein S. Factor V Leiden deficiency and prothrombin gene mutations are some of the more common thrombophilias, with a slight increased risk for venous thromboembolism (VTE). Current guidelines suggest the use of low-molecular weight heparins for secondary prophylaxis in patients with VTE. However, there is a lack of data on the use of Direct Oral Anticoagulant (DOACs) in patients with inherited thrombophilia. We evaluated our use of rivaroxaban in patients with thrombophilia disorders treated for secondary DVT prophylaxis. Method We performed a retrospective evaluation of patients in our institution with inherited thrombophilia with an active VTE diagnosis who received DOACs for secondary prophylaxis from November 2013 until April 2016. Data collected included patient demographics, inherited thrombophilia mutation, previous history of VTE, prior treatments, and efficacy and safety of anticoagulation with DOACs. Results We had 13 patients with inherited thrombophilia mutation and 4 patients diagnosed with concomitant cancer (non-Hodgkin lymphoma, melanoma, and 2 with breast cancer) (Table 1). Out of 13 patients 3 failed warfarin, and one failed fondaparinux prior to switching to a DOAC. Mutation with heterozygous Factor V Leiden deficiency was reported in 7 patients, while mutations with Protein C and/or S deficiency were found in 4 patients. One patient had both Factor V Leiden and Protein C deficiency mutations. The prothrombin gene mutation was identified in one patient. The median of length of therapy was 2 years with 8/13 still on rivaroxaban in April 2016. The shortest treatment duration was 41 days for a patient who failed rivaroxaban with a second clot and was switched to apixaban without subsequent treatment failure. Two patients experienced 4 non-major episodes of gastrointestinal bleeding, nose bleeding and dark stool. One patient developed rash with noted bruising during their rivaroxaban therapy. Conclusion: This is the first report on outcomes for secondary DVT prophylaxis with DOACs in patients with underlying thrombophilia mutations. Safety and efficacy of DOACs for secondary VTE prophylaxis yielded favorable results; however, future prospective studies in the setting of thrombophilia are warranted. Table 1 Summary of baseline characteristics and outcomes. Table 1. Summary of baseline characteristics and outcomes. Disclosures McBride: Sanofi: Research Funding.

A multi-laboratory assessment of congenital thrombophilia assays performed on the ACL Top 50 family for harmonisation of thrombophilia testing in a large laboratory network

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Emmanuel J. Favaloro ◽  
Soma Mohammed ◽  
Ronny Vong ◽  
Kent Chapman ◽  
Priscilla Swanepoel ◽  
...  
Keyword(s):  
Protein C ◽  
Factor V Leiden ◽  
Poor Performance ◽  
Protein S ◽  
Third Party ◽  
Factor V ◽  
Reference Ranges ◽  
Laboratory Assessment ◽  
Study Objective ◽  
Thrombophilia Testing

Abstract Objectives Thrombophilia testing is commonly performed within hemostasis laboratories, and the ACL TOP 50 family of instruments represent a new ‘single platform’ of hemostasis instrumentation. The study objective was to evaluate these instruments and manufacturer reagents for utility of congenital thrombophilia assays. Methods Comparative evaluations of various congenital thrombophilia assays (protein C [PC], protein S [PS], antithrombin [AT], activated protein C resistance [APCR]) using newly installed ACL TOPs 550 and 750 as well as comparative assessments with existing, predominantly STAGO, instrumentation and reagents. Verification of manufacturer assay normal reference ranges (NRRs). Results HemosIL PC and free PS assays showed good comparability with existing Stago methods (R>0.9) and could be considered as verified as fit for purpose. HemosIL AT showed high relative bias with samples from patients on direct anti-Xa agents, compromising utility. Manufacturer NRRs for PC, PS and AT were verified with minor variance. Given the interference with direct anti-Xa agents, an alternate assay (Hyphen) was evaluated for AT, and the NRR also verified. The HemosIL Factor V Leiden (APC Resistance V) evidenced relatively poor performance compared to existing assays, and could not be adopted for use in our network. Conclusions This evaluation of HemosIL reagents on ACL TOP 50 Family instruments identified overall acceptable performance of only two (PC, free PS) of four thrombophilia assays, requiring use of third-party reagents on ACL instruments for the other two assays (AT, APCR).

Thrombophilia Testing Practices: The Mayo Clinic Experience

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 39-40
Author(s):  
Caleb J Scheckel ◽  
Rajiv K. Pruthi ◽  
Ariela L. Marshall ◽  
Aneel A. Ashrani ◽  
Dong Chen ◽  
...  
Keyword(s):  
Mayo Clinic ◽  
Protein C ◽  
Factor V Leiden ◽  
Choosing Wisely ◽  
Prothrombin G20210a ◽  
Reference Laboratory ◽  
Factor V ◽  
Clinic Staff ◽  
G20210a Mutation ◽  
Thrombophilia Testing

Introduction: The 2013 ASH Choosing Wisely campaign recommends against thrombophilia testing in patients with major transient risk factors for venous thromboembolism (VTE). Our Special Coagulation Laboratory (SCL) offers an algorithmic approach to thrombophilia testing which includes assays for lupus anticoagulant, dysfibrinogenemia, anticoagulant proteins (protein C, protein S, antithrombin), activated protein C resistance with reflex to factor v Leiden (if indicated), and prothrombin G20210A mutation. Samples are received through Mayo Clinic Laboratories (MCL), national and international reference laboratory (often with limited or no clinical information) and from internal Mayo Clinic practice. We hypothesized that thrombophilia testing would decline in cases where it was recommended against following the publication of testing guidelines. Methods: We audited the external thrombophilia testing samples between2013-2019 and internal samples between 2014-2019 (periods during which they were available). For the internal samples, complete test volumes were only available 2014-2019. Because external clients may either adopt internal testing or contract with a different reference laboratory, many clients may not have been retained over the entire observed period. To better understand the ordering practices of consistent clients, external clients which did not have thrombophilia testing sent to MCL each year of the observed period were excluded. We separated internal ordering practices by hematology and oncology or thrombophilia clinic staff and trainees contrasted with those of other specialties. Results: MCL received 18,529 external thrombophilia testing samples from 322 external healthcare systems during the observed period. From 37 clients, 5,878 (38.2%) samples met inclusion criteria. Annual volume of samples ranged from 890 in 2013 to 861 in 2019 (861-1046). Special coagulation lab processed 11,639 internal thrombophilia tests during the observed periods. There was a consistent small annual increase in testing with 1,398 performed in 2014 and 2,430 in 2019. Of 11651 tests ordered, only 18.6% (2167) were ordered by people most likely to be familiar with ASH choosing wisely campaign. Annual thrombophilia testing ordered by hematology and oncology or thrombophilia clinic staff increased from 307 in 2014 to 387 in 2019 (307-432). However, the ordering practices of these providers as a proportion of overall practices declined from 22.0% (307/1398) in 2014 to 15.9 % (387/2430) in 2019. Table Discussion: Our preliminary data showed no significant trend in thrombophilia ordering practices among included external clients since publication of the ASH Choosing Wisely guidelines on thrombophilia testing. Internally we found a consistent small rise in numbers of thrombophilia tests ordered since 2014 but this may reflect changes in patient volume. We observed that the majority of internal thrombophilia testing was ordered by non-hematology/oncology or thrombophilia providers who are perhaps less likely to be familiar with ASH Choosing Wisely guidelines. The proportion of testing ordered by hematology & oncology or thrombophilia providers declined during the observed period. Our findings are limited by lacking information on the indication and appropriateness for testing as well as possibility of change in patient population. However the overall trend in test volumes and specialty of ordering providers deserves attention and highlight the value in educating other medical societies on ASH Choosing Wisely recommendations for thrombophilia testing. Future work will focus on appropriateness for thrombophilia testing including the indication and time (remote from anticoagulation and acute thrombotic episode), location of testing (inpatient vs. outpatient), as well as investigating if testing has changed patient management, which may help in creating new Choosing Wisely recommendations for thrombophilia testing. Figure 1. Disclosures Pruthi: HEMA Biologics: Honoraria; Bayer Healthcare: Honoraria; Merck: Honoraria; Instrumentation Laboratory: Honoraria; Genentech Inc.: Honoraria; CSL Behring: Honoraria.

Prevalence of Activated Protein C Resistance Due To Factor V Leiden Mutation among South Asians (India and Pakistan) with Venous Thromboembolism.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 4043-4043
Author(s):  
Sirisha Perumandla ◽  
Yelena Patsiornik ◽  
Neetha Mahajan ◽  
Anju Ohri
Keyword(s):  
Protein C ◽  
Chart Review ◽  
South Asians ◽  
Activated Protein C ◽  
Factor V Leiden ◽  
Factor V ◽  
Inherited Thrombophilia ◽  
Apc Resistance ◽  
Fv Leiden ◽  
Work Up

Abstract Objective: To study the prevalence of Activated Protein C (APC) resistance due to Factor V Leiden (FV Leiden) mutation among the first generation immigrants from India and Pakistan with venous thromboembolism (VTE). Introduction: APC resistance due to the substitution of Arginine 506 by Glutamine in coagulation Factor V is caused by G1691A mutation in exon 10 of Factor V gene. This is the commonest cause of inherited thrombophilia in Caucasians, but the frequency of this mutation is low in non-Caucasians. Among subjects in the Physician Health Study, the frequency of FV Leiden was found to be 5.27% in Caucasian Americans vs. 0.45% in Asian Americans. Another study found no mutation in 191 Asian Americans tested. In non-Caucasians with VTE, it is generally considered not cost effective to screen for this mutation. However Asians are a heterogeneous group and the Leiden gene frequency varies among different ethnic populations. While the frequency of FV Leiden gene has been documented to be low in China, Korea, Japan, Thailand, Indonesia etc, the frequency in India and Pakistan is not well studied. Two studies found a carrier frequency of 2% (Rees et al) and 4.2 % (Gou et al) among the general population from India and Pakistan. This is similar to the frequency found in Middle Eastern and European population. We did not come across any study of FV Leiden gene frequency in patients with VTE from India and Pakistan. Patients and Methods: A retrospective chart review of patients of Indian or Pakistani origin seen at Coney Island Hospital, from July 1996 to June 2003, who had a work up for inherited thrombophilia after an episode of VTE. During the chart review age, sex, first or recurrent episode and any predisposing factors such as immobilization, malignancy, hormonal therapy, surgery, pregnancy, and the presence of SLE or MPD were noted. Thrombophilia work up included functional assays for Protein C, S and Antithrombin III, Lupus anticoagulant, ACA and Homocysteine levels. APC resistance was measured by a clotting assay using Factor V depleted plasma and all patients who were borderline or resistant were tested for the presence of FV Leiden mutation by PCR. Results: A total of 18 patients were studied. All had an episode of VTE documented by a Doppler ultrasonography or a Ventilation Perfusion lung scan or a CT angiogram. 3 out of 18 patients (16.6%) had APC resistance. All the three patients were confirmed to be heterozygous for FV Leiden mutation. Two were male and one was a female with a median age of 36 yrs (27, 36 and 57 yrs). The female patient had a recurrent episode, first one occurred during pregnancy, but the second episode had no precipitating events. One male patient had trauma to the leg and was immobilized at the time of the VTE, another male patient was a cab driver by occupation. None of the patients had any other concurrent inherited thrombophilic state. Conclusions: The prevalence of the FV Leiden mutation is significantly high among South Asians with VTE in our study. If the findings are confirmed by a larger study, screening for this mutation for thrombophilia would be relevant in patients of South Asian origin and screening recommendations for family members would be identical to Caucasian population. The high prevalance as in Caucasians suggests a founder effect and possible spread of the mutation by the migration of Neolithic farmers from the Middle East towards Europe and India, ten thousand years ago. This has been confirmed by haplotype analysis.

Retrospective Cohort of Unprovoked Venous Thromboembolism Patients: What Proportion Have Potent Thrombophilias Necessitating Indefinite Anticoagulants?

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 2318-2318
Author(s):  
Junghyun Park ◽  
Marc Rodger
Keyword(s):  
Protein C ◽  
Factor V Leiden ◽  
Protein S ◽  
Factor V ◽  
Gene Variant ◽  
Anticoagulation Management ◽  
Antithrombin Deficiency ◽  
S Deficiency ◽  
Prothrombin Gene ◽  
Thrombophilia Testing

Introduction Thrombophilia testing in unprovoked venous thromboembolism patients (VTE) is controversial. Common thrombophilias such as Factor V Leiden or prothrombin gene variant appear to not importantly increase the risk of VTE recurrence, and thus are not considered in anticoagulation management decisions. However, patients with potent thrombophilias such as antiphospholipid antibodies (APLA), antithrombin deficiency, protein C and S deficiency, and homozygous genetic thrombophilias or combined defects are at higher risk of recurrence and it is recommended that they receive long-term anticoagulation. If the proportion of patients with "potent" thrombophilia is high then thrombophilia testing should be conducted. We sought to determine the proportion of unprovoked VTE patients with "potent" thrombophilia. Methods All patients with managed in our oral anticoagulation management system in the period from 1998 to 2015 were potentially eligible for the study. Inclusion criteria were: 1) symptomatic, objectively confirmed VTE unprovoked proximal deep vein thrombosis or pulmonary embolism. Exclusion criteria were: 1) cancer or myeloproliferative disease at the time of VTE diagnosis; 2) no cast, surgery, trauma or immobilization (>3 days in bed 90% of waking hours) in the 90 days prior to diagnosis. We selected unprovoked VTE patients diagnosed between 2002 and 2010, as thrombophilia testing was relatively universal and available in our electronic system in that time frame (N=1344). We then selected a convenience sample of N=1165. The primary outcome measure was the proportion of patients with "potent" thrombophilia (potent= homozygous Factor V Leiden, homozygous Prothrombin gene variant, APLA, protein C, protein S or anti-thrombin deficiency or combined deficiencies). Results In 1165 patients with unprovoked VTE, complete screening was done in 470 patients (40.34%) and 976 (83.78%) had at least one thrombophilia test. Complete thrombophilia testing was defined as a screen including testing for factor V Leiden, prothrombin gene defect, APLA, anti-thrombin deficiency, protein C, and protein S. Potent thrombophilias were demonstrated in 103/1165 patients (8.84%; 95% CI, 7.34 to 10.61) (Table 2) in the total study population, and 103/976 (10.55%; 95% CI, 9.62-14.47) in patients with at least one thrombophilia test. Conclusion The proportion of unprovoked VTE patients with "potent" thrombophilia is high. Given a high proportion of "potent' thrombophilia patients who likely benefit from indefinite anticoagulation, complete thrombophilia testing appears warranted in patients with unprovoked VTE in whom anticoagulants maybe discontinued. Thrombophilia testing is warranted for a selected group of patients to detect high-risk thrombophilias that could impact anticoagulation management. Table 1. Thrombophilia screening Complete screening 470 (40.3%) No screening 189 (16.2%) At least one thrombophilia test 976 (83.8%) Table 2. Thrombophilia All patients (n=1165) Tested for individual thrombophilia % 95% CI % 95% CI FVL Heterozygous 162/1165 (13.9%) 12.0-16.0% 162/883 (18.4%) 15.9-21.0% FVL Homozygous 4/1165 (0.3%) 0.1-0.9% 4/883 (0.5%) 0.2-1.2% Prothrombin Heterozygous 63/1165 (5.4%) 4.3-6.9% 63/831 (7.6%) 6.0-9.6% Prothrombin Homozygous 1/1165 (0.0%) 0.0-0.5% 1/831 (0.1%) 0.0-0.7% Antithrombin deficiency 10/1165 (0.9%) 0.5-1.6% 10/815 (1.2%) 0.7-2.2% Protein C deficiency 18/1165 (1.6%) 1.0-2.4% 18/639 (2.8%) 1.8-4.4% Protein S deficiency 13/1165 (1.1%) 0.7-1.9% 13/635 (2.1%) 1.2-3.5% Lupus anticoagulant 24/1165 (2.1%) 1.4-3.1% 24/849 (2.8%) 1.9-4.2% Anticardiolipin IgM 16/1165 (1.4%) 0.9-2.2% 16/886 (1.8%) 1.1-2.9% Anticardiolipin IgG 20/1165 (1.7%) 1.1-2.6% 20/885 (2.2%) 1.5-3.5% β-2 microglobulin IgM 10/1165 (0.9%) 0.5-1.6% 10/333 (3.0%) 1.6-5.4% β-2 microglobulin IgG 8/1165 (0.7%) 0.4-1.4% 8/333 (2.4%) 1.2-4.7% Homocysteine 50/1165 (5.7%) 4.3-7.4% 50/668 (7.5%) 5.7-9.7% Factor VIII elevated 11/1165 (0.9%) 0.5-1.7% 11/646 (1.7%) 1.0-3.0% At least one or more of the above 331/1165 (28.4%) 25.9-31.1% 331/976 (33.9%) 31.0-36.9% Potent thrombophilia 103/1165 (8.8%) 7.34-10.6% 103/976 (10.6%) 9.6-14.5% Figure 1. Figure 1. Disclosures No relevant conflicts of interest to declare.

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