Humble Aspirin Betters Costly Anticoagulants as VTE Prophylaxis

Aspirin, by itself, may be sufficient to balance the risks of venous thromboembolism (VTE) and bleeding following total knee joint replacement surgery, according to a 41,537-patient study of knee patients at 29 hospitals in Michigan.

Led by University of Michigan’s Brandon R. Hood, M.D., the research team designed the study “… to compare rates of bleeding and a composite of VTE events (pulmonary embolism, deep vein thrombosis or death) in patients receiving various types of anticoagulant therapies, if any.”

“While nearly all orthopedic surgeons agree that pharmacologic prophylaxis is the standard of care, major disagreements remain about the optimal, or even acceptable, medication regimens,” wrote Robert S. Sterling, M.D., and Elliott R. Haut, M.D., Ph.D.—both with Johns Hopkins University School of Medicine—in an accompanying JAMA Surgery editorial. “Even evidence-based guidelines from different national societies, using the same published literature, often make different recommendations.”

“Aspirin was the monotherapy prophylaxis of choice by 30.9 percent of the physicians participating in the study.  Other types of anticoagulants were used by 54.5 percent of the physicians and 1.6 percent of the physicians prescribed no anticoagulant and 13 percent prescribed both aspirin and another anticoagulant. Other anticoagulants were factor Xa inhibitors, warfarin and low-molecular-weight heparin (LMWH).”

How many of the 41,537 patients reported a VTE primary outcome? Here are the summary results and, notably, the best (and least expensive) outcomes were amongst the aspirin-only patients.

• 16 percent of patients taking aspirin only
• 42 percent of patients taking another anticoagulant only
• 31 percent of patients taking aspirin plus another anticoagulant
• 79 percent of patients had no pharmacotherapy

“Similarly, the rates of major bleeding at 90 days were lowest for those taking aspirin alone (0.90 percent), followed by anticoagulation alone (1.14 percent), a combination of the two therapies (1.35 percent) and no drug prophylaxis (1.50 percent).”

“Aspirin easily cleared the bar of noninferiority for which the study was powered, demonstrating relative risk reductions of 15 percent for VTE and 20 percent for bleeding events compared to other drug-based therapies.:

“There are several reasons to prefer using aspirin for VTE prophylaxis in the appropriately screened patient,” Hood and colleagues wrote. “Aspirin administration is simple, safe, and does not require monitoring. Although this study did not find a significant difference, a 2008 practice survey conducted by the American Association of Hip and Knee Surgeons found that while most orthopedic surgeons felt LMWH to be most efficacious, aspirin was felt to be the easiest to use with the lowest risk of bleeding or wound complications.”

“The researchers also pointed out that aspirin is the most affordable of the anticoagulant options, with a price tag of around $2 per month.”

“The reported cost for a 30-day supply of rivaroxaban is approximately $379 to $450, and that of LMWH is estimated at $450 to $890,” they wrote. “Warfarin costs a few dollars for a 30-day course, but with monitoring considered; the cost approaches that of the other anticoagulants. … These cost differences could have a substantial association with a patient’s out-of-pocket expenses as well as the cost of a hospital’s overall bundle in the new episode payment models,” noted writer Daniel Allar in the publication Cardiovascular Business article Aspirin enough to prevent VTE after knee replacement surgery.