No Indication for APTT Screening in Patients on Oral Anticoagulant Therapy

Summary

Patients on oral anticoagulant therapy (OAT) may bleed due to a very low factor IX level caused by a mutation at Ala-10 in the propeptide region of the 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 disproportionately prolonged APTT. In these patients the factor IX level, the mutation 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 the Ala-10 mutation in the factor IX gene.

• References

• 1 Chu K, Sheue-Mei W, Stanley T, Stafford DW, High KA. A mutation in the propeptide of factor IX leads to warfarin sensitivity by a novel mechanism. J Clin Invest 1996; 98: 1619-25.
• 2 Oldenburg J, Quenzel E-M, Harbrecht U, Fregin A, Kress W, Muller CR, Hertfelder H-J, Schwaab R, Brackmann H-H, Hanfland P. Missense mutations at ALA-10 in the factor IX propeptide: an insignificant variant in normal life but a decisive cause of bleeding during oral anticoagulant therapy. Br J Haematol 1997; 98: 240-4.
• 3 Van der Meer FJM, Rosendaal FR, Vandenbroucke JP, Briët E. Bleeding complications in oral anticoagulant therapy: an analysis of risk factors. Arch Int Med 1993; 153: 1557-62.
• 4 Peters J, Luddington R, Brown K, Baglin C, Baglin T. Should patients starting oral anticoagulant therapy be screened for missense mutations at Ala-10 in the factor IX propeptide?. Br J Haematol 1997; 99: 467-8.
• 5 Van der Meer FJM, Rosendaal FR, Vandenbroucke JP, Briët E. Assessment of a bleeding risk index in two cohorts of patients treated with oral anticoagulants. Thromb Haemost 1996; 76: 12-6.