Chris Tully MD
Faculty peer reviewed
What is the number of patients needed to prophylax to prevent an episode of venous thromboembolism in a hospitalized medical patient?
The use of prophylactic anticoagulation for venous thromboembolism (VTE) is considered standard of care in the inpatient medical setting in order to prevent deep venous thrombosis (DVT) and fatal and nonfatal pulmonary embolism (PE). While a majority of the knowledge stems of post-surgical patients, there has been an increasing volume of research emphasizing and illustrating the benefit in hospitalized medical patients. Three randomized controlled trials examined this question of anticoagulation with three different pharmacologic treatments, enoxaparin, dalteparin (LMWHs) and fondaparinux (inhibitor activated factor X). In each case there was a significant reduction in the incident of VTE. See results below:
|Intervention (vs. placebo)||Absolute Risk Reduction (ARR)||Number needed to treat (NNT)||P value||Relative Risk Reduction (RRR)|
|Enoxaparin 40mg daily||9.4%||11||<0.001||63%|
|Dalteparin 5000U daily||2.2%||45||=0.002||44%|
|Fonadparinux 2.5mg daily||4.9%||21||=0.03||47%|
Another common choice in the prevention of VTE is the use of unfractionated heparin (UFH) given the high cost of treatment associated with LMWHs or factor Xs inhibitors. A meta-analysis comparing UFH and LMWH showed no significant difference in DVT, PE or death between the two interventions. While there was a statistically significant decreased risk of major bleed with LMWH in this meta-analysis, the ARR was 0.0076%, and therefore the NNT with LMWH to prevent one major bleed would be 13,157 patients, meaning that UFH is still a safe and appropriate solution.
Either way, in hospitalized patients, prophylactic anticoagulation is a critical and important element of appropriate patient care.
Faculty peer Reviewed by Kelly Crotty MD, NYU Division of General Internal Medicine
Francis C. Prophylaxix for Thromboembolism in Hospitalized Medical Patients. N Engl J Med 356:1438, April 5, 2007
Mismetti P, Laporte-Simitsidis S, Tardy B, et al. Prevention of venous thromboembolism in internal medicine with unfractionated or low molecular weight heparins: a meta-analysis of randomised clinical trials. Thromb Haemost 2000:83: 14-9.