A total of 211 positive work-ups (6%) led to an appropriate decision to extend or initiate anticoagulation; 82 positive work-ups (2.2%) were inappropriately overlooked—21 (26%) with antiphospholipid antibody syndrome, 20 (24%) with heterozygous factor V Leiden mutation and 14 (17%) with heterozygous prothrombin 20210G>A mutation. The gene discussed is F5; the disease is antiphospholipid syndrome.