Clinical Decision Rule Validation Study to Predict Low Recurrent Risk in Patients With Unprovoked Venous Thromboembolism

REVERSEII: Validation of the "Men and HERDOO2"- A Clinical Decision Rule to Identify Patients With "Unprovoked" Venous Thromboembolism Who Can Discontinue Anticoagulants After 6 Months of Treatment.

The main objective of this study is to verify whether a new clinical decision rule identifying patients diagnosed with unprovoked blood clots who have a low risk of recurrence can safely stop oral anticoagulant therapy after 5-7 months of treatment.

Up to 50% of patients with a first episode of venous thromboembolism (VTE) have no identifiable cause (i.e. are unprovoked VTEs). The risk of recurrent VTE in this large group of patients with unprovoked VTE after 3-6 months of anticoagulant therapy is 5-10.8% in the year following discontinuation of oral anticoagulant therapy. One in six to one in twenty recurrences of a new VTE are fatal. Given the intermediate risks of recurrence in unselected unprovoked VTE patients, clinicians do not have clear guidance on whether to continue or discontinue anticoagulants in patients with unprovoked VTE. Recently attention has turned to the concept of risk stratification to identify subgroups of patients with unprovoked VTE who could safely discontinue oral anticoagulation therapy (OAT).

In the REVERSE I study, a clinical decision rule derivation study conducted from 2001 to 2006, we developed and internally validated the clinical decision rule "Men continue and HER DOO2" that identifies patients with a first unprovoked VTE who likely have a low risk of recurrent VTE and could safely discontinue OAT subsequent to 5-7 months of OAT. The present study will evaluate if the "Men continue and HER DOO2" rule (comprised of gender, elevated D-dimer levels, post-thrombotic signs, obesity, and older age) is safe, clinically useful, and reproducible when prospectively implemented in multiple centers and a variety of settings. If this clinical decision rule is validated, it will provide physicians with important information to allow them to more confidently identify unprovoked VTE patients at low risk of VTE recurrence who may not need to continue OAT.

Inclusion Criteria:

• First episode of major unprovoked VTE
• VTE objectively proven
• VTE treated for 5-12 months with anticoagulant therapy authorized for the REVERSE II study (initial or ongoing therapy)
• Absence of recurrent VTE during the treatment period

Exclusion Criteria:

• Less than 18 years of age
• Patients who have already discontinued anticoagulant therapy
• Patients requiring ongoing anticoagulation for reasons other than VTE
• Being treated for a recurrent unprovoked VTE
• Patients with high risk thrombophilia
• patients who plan on using exogenous estrogen(OCP,HRT)if anticoagulant therapy is discontinued
• Patients with pregnancy associated VTE
• Geographically inaccessible for follow-up
• Patients unable or unwilling to provide informed consent