Oral contraceptives and venous thromboembolism: should epidemiologic associations drive clinical decision making?

摘要: New studies linking use of oral contraceptives (OCs) containing a third generation progestogen with venous thromboembolism (VTE) have stirred controversy. Epidemiologists face the task separating direct effect OC from confounding pre-existing factor (e.g. smoking). Only 1-2% VTE cases are fatal. The percentage that diagnosed and treated in hospital is low falling. A major challenge epidemiologic study non-fatal conditions clinical social factors will also affect whether or when where diagnosis made. newest OCs were based on hospital. They found risks for among users to be about 2-4 times higher than those non-users 1.5-2 using levonorgestrel-containing OCs. In past laboratory pointed estrogen dose as main risk thus lower less likely contribute older Yet new an increased doses estrogen. There has been consistency findings leading some conclude causation explains findings. re-analysis data these highest relative occurred recently introduced desogestrel-containing only 20 mcg ethinyl estradiol. it would expected safer other authors concluded clinicians may assumed each should they selectively prescribing them women. Since association between weak there no biologic explanation one not consider causal. Physicians all evidence before changing prescription practices. Clinical actions associations undermine their credibility epidemiologists.