The association of incident clot location and the risk of VTE recurrence

Abstract

Recurrent venous thromboembolism (VTE) affects 16-30% of individuals who have experienced an incident VTE event, according to recent population-based studies conducted in the United States. Researchers and healthcare providers have worked to estimate recurrence risk among individuals to assess proper use and duration of anticoagulants and other therapies to prevent recurrence after an incident clot. Among risk estimation methods are risk-scoring systems that include recognized risk factors. Our study used population-based Group Health Cooperative (GHC) data to evaluate incident clot location on risk of recurrent VTE. Using Cox proportional hazards regression, we compared risk of recurrence among subjects who had distally located incident deep vein thrombosis (DVT) and subjects who had incident pulmonary embolism (PE) with subjects who experienced an incident DVT clot in a proximal location. After adjusting for race, age, sex, BMI, and smoking status, we observed lower risk of recurrence among subjects with distal incident clots (HR 0.44 [95% CI 0.29-0.66]) and pulmonary embolism (HR 0.61 [95% CI 0.50-0.74]) when compared with subjects with incident clots in a proximal location. This research supports the inclusion of incident clot location as a factor in future recurrence risk scoring systems as well as in general medical practice. Future research may benefit from further evaluation of the idiopathic subgroups and the potential differing risk within them, particularly among subjects with cancer-provoked incident clot, who experienced a higher rate of recurrence than other groups. Additionally, we suggest further differentiation of regions of incident clot location as it relates to recurrence risk, including a more granular evaluation of individual leg veins.