Modeling approach for determining the effect of thrombophilia testing. Population considered for testing: Figure 1 with the guideline flowchart for the different populations for which a recommendation regarding thrombophilia testing was provided. Thrombophilia: any type of thrombophilia or a specific type, depending on whether the recommendation question addresses panel testing or testing for a known specific type in the family. Intervention: course of action other than “usual care.” Depending on the specific question, this means prescribing thromboprophylaxis, withholding thromboprophylaxis, extending thromboprophylaxis, stopping thromboprophylaxis, withholding COCs, or withholding HRT. Usual care: for populations where “usual care” was ambiguous, 2 scenarios were modeled, and separate recommendations were provided (see recommendations 7-10).