Effect of information on the perception of users and prospective users of combined oral contraceptives regarding the risk of venous thromboembolism

This study evaluated patients' knowledge on the risk of venous thromboembolism (VTE) associated with combined oral contraceptives (COCs) and their perception of this risk when it is presented as a relative risk (RR), absolute risk (AbR) or attributable risk (AR). This was a cross-sectional study involving 159 users or potential users of COCs. The participants answered a self-administered questionnaire in which the risk of VTE associated with COCs was presented as RR, AbR and AR. The degree of concern expressed regarding this risk and the women's changes of opinion when the information was communicated through a different risk model were evaluated. Most of the women (67.9%) expressed concern when the risk was presented as an RR. Conversely, they showed no concern when the risk was presented as an AbR (14.5%) or AR (10.7%). A significant number of women changed their opinion regarding their level of concern when the risk was presented as an AbR or AR (p < 0.001). In conclusion, concerns about thrombotic complications from the use of combined hormonal contraception is reduced when incidence rather than relative risk is presented. Presentation of thrombosis complications in terms of incidence rather than RR may improve communication of side effects during counseling for combined hormonal contraception initiation.