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

Abstract

The risk of late recurrence after venous thromboembolism (VTE) related to weak transient risk factors (RFs) in young women guides thromboprophylaxis. 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. We performed a multicentre, international, observational, retrospective study on women aged 18-55 years old, free from high-risk thrombophilia and subsequently monitored. 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. 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.