Letters Section Editor: Robert M. Golub, MD, Senior Editor.
To the Editor: We believe that the study by Dr Ost and colleagues1 of duration of anticoagulation following venous thromboembolism is missing important data on bleeding risk that are needed for clinicians and patients to make fully informed decisions about how long to continue secondary prophylaxis.
Randomized trials often report lower bleeding rates than do studies of community outpatients.2 This discrepancy may be due to closer monitoring of international normalized ratio, better education of participants about food and drug interactions, or stringent participant selection.3 The appropriate incidence rate ratio for bleeding is not one pooled from clinical trials, but from epidemiologic studies, which are lacking. As a surrogate, if rates of major bleeding are 0.4% per year without warfarin,4 and 1% per year4 to 7.22% per year3 with warfarin, the number needed to harm with 1 additional year of anticoagulation may be approximately 14 to 167. Alternatively, clinicians could identify patients at high risk for bleeding by using validated scores, which are imperfect but more reliable than intuitive estimates alone.2,5
Krakow E, Ortel TL. Continuing Anticoagulation Following Venous Thromboembolism. JAMA. 2005;294(24):3088-3089. doi:10.1001/jama.294.24.3088-a