Family history and risk of venous thromboembolism with oral contraception

Editor—Cosmi et al in their article claim that family history has poor diagnostic test qualities to detect prothrombotic mutations.¹ They also indicate that overall population screening is not cost effective. Although it always was obvious that family history would never make a perfect test (of families with many cases of venous thrombosis, up to 40 or 50% have factor V Leiden²), the finding of an equal predictive value for a positive and a negative family history by Cosmi et al is surprising and might be due to the small numbers included or the type of history that was considered “positive.”

Even if family history is far from perfect as a diagnostic test for one or two mutations, the question is whether one should refrain from using it. In our original publication, we tried to emphasise the meaning of family history for the prescription of oral contraceptives, and not really as a clue for the detection of mutations.³ Apart from any prothrombotic mutation, a strongly positive family history might point to a tendency for venous thrombosis that might be taken into account clinically in the decision whether or not to use oral contraceptives.

Moreover, even the meaning of a mutation is different in the context of a positive family history: the age at first venous thrombosis with factor V Leiden is about 10 years younger in persons with a positive family history than in consecutive patients.⁴ The most important information that one would like to obtain from a family history is not a proxy test for factor V Leiden or any other mutation, but the likelihood that a woman will develop thrombosis if she uses oral contraceptives. Whether or not family history would be valuable for that purpose is the ultimate test.