Venous thromboembolism associated with weak transient risk factors in young women: risk of late recurrence. An international cohort study

Abstract

Background: The risk of late recurrence after venous thromboembolism (VTE) related to weak transient risk factors (RFs) in young women guides thromboprophylaxis.

Objective: To estimate the incidence of recurring VTE in untreated women with a first episode due to combined oral contraceptives (COCs), pregnancy-puerperium, minor trauma-fracture, brief surgery, infection or brief immobility.

Methods: We performed a multicentre, international, observational, retrospective study on women aged 18-55 years old, free from high-risk thrombophilia and subsequently monitored.

Results: We studied 7,754 women over 43,880 patient.years (p.y.) and observed 1,318 VTE recurrences, corresponding to 3.00 (2.84-3.16) events for 100 p.y. Rates were higher if the initial clinical RF was pregnancy/puerperium, infection or brief surgery. Non-O blood group, the 3^rd tertile of FIX activities and the 2^nd and 3^rd tertiles of FVIII activities were independent predictors of VTE recurrence. The overall risk of recurrence was 2.92 (2,66-3.18) per 100 p.y. in the subgroup of women with proximal deep vein thrombosis or pulmonary embolism. Class 1 obesity, the 3^rd tertile of FIX activities and the 2^nd and 3^rd tertiles of FVIII activities were predictors. Combinations of predictors suggested that they might help define sub-groups that could benefit from chronic thromboprophylaxis.

Conclusion: We confirm that young women with a first VTE related to weak transient RFs have an overall limited, but not anecdotal, risk of late recurrence, higher than 3% per year in subgroups. This risk is modulated by predictors, including categories of factors VIII and IX values, which could help to design the large-scale prospective studies still required.

Keywords: Deep vein thrombosis; Pulmonary embolism; Recurrence; Risk factor; Venous thromboembolism; Women.