In Reply We appreciate the suggestion of Amini et al that the number needed to treat (NNT) and the number needed to harm (NNH) will help inform clinicians in interpreting the results of our study. Although we agree with the theme of their comments, we note a few important considerations.
First, we urge readers to remember that the primary outcome of our study was proximal deep vein thrombosis (DVT) or pulmonary embolism (PE) within 180 days, not solely DVT or solely PE. Accordingly, we contend that the NNT should account for both DVT and PE. Because anticoagulation was associated with a reduction in the incidence of DVT or PE from 13 of 141 participants (9.2%) to 8 of 243 participants (3.3%), the NNT for this combined outcome is, on average, 16.9. As Amini et al describe, the NNH for bleeding was 15.4.
Utter GH, Salcedo ES, White RH. The Risks and Benefits of Treating Isolated Calf Deep Vein Thrombosis—Reply. JAMA Surg. Published online February 15, 2017. doi:10.1001/jamasurg.2016.5563