No indication for APTT screening in patients on oral anticoagulant therapy

Patients on oral anticoagulant therapy (OAT) may bleed due to a very low fa ctor IX level caused by a mutation at Ala-10 in the propeptide region of th e factor IX gene. We evaluated screening of patients on OAT with an APTT to detect patients with this abnormality. In 734 patients an APTT was assessed. Twenty-three patients had a dispropor tionately prolonged APTT. In these patients the factor IX level, the mutati on at Ala-10 and the frequency of bleeding complications were assessed. No severely lowered factor IX levels were found (1 patient with 5% factor IX). No mutations at Ala-10 were found and bleeding complications were not more frequent in these patients. Conclusion: Routine APTT screening of patients on OAT is not useful to detect patients with increased bleeding or with th e Ala-10 mutation in the factor IX gene.