Aspirin Is as Effective as Newer Anticoagulants in Preventing VTE after TKA, Study Finds
A study recently published online by JAMA Surgery reports that the use of aspirin may be just as effective as the use of newer, more expensive anticoagulants such as enoxaparin (Lovenox) and rivaroxaban (Xarelto) in preventing venous thromboembolism (VTE) after primary total knee arthroplasty – which could help reduce costs for the nearly 1 million Americans who have knee replacement surgery each year.
During the 2-year study period, aspirin use rose from 10% to 50% among patients managed by orthopaedic surgeons participating in the Michigan Arthroplasty Registry Collaborative Quality Initiative, a statewide effort to give patients the best possible recovery and outcomes after hip and knee arthroplasty. Since 2015, the shift has become even more distinct: Aspirin prescribing has risen to 70% among Michigan orthopaedic surgeons.
“This study is truly a real-world experience of what happened in Michigan when the majority of surgeons switched to aspirin,” said lead study author Brian R. Hallstrom, MD, an orthopaedic surgeon and associate chair for quality and safety at the University of Michigan Department of Orthopaedic Surgery. Dr. Hallstrom is also co-director of the initiative and a health services researcher at U-M’s Institute for Healthcare Policy and Innovation.
“The incidence of blood clots, pulmonary embolus, and death did not increase despite this dramatic change in practice,” he said.
The U-M study involved more than 41,000 patients who underwent primary total knee arthroplasty at the 29 Michigan hospitals in the surgical quality group between April 1, 2013, and October 31, 2015. Patients were monitored for VTE for 90 days after surgery.
One-third of the patients took aspirin alone, 54% took only an anticoagulant, and 13% took an aspirin/anticoagulant combination. Only just 1.16% of aspirin patients developed VTE, as did 1.42% of anticoagulant patients. This was not a statistically significant difference.
Although neither drug appeared better than the other, aspirin has some obvious advantages. “Aspirin is easy to take and much less expensive,” Dr. Hallstrom said. “Patients can get it over the counter for pennies, while the other anticoagulants require monitoring, injections, and frequent dose adjustments and are extremely expensive.”
The reported cost for a 30-day supply of rivaroxaban is approximately $379 to $450; heparin is estimated at $450 to $890. Although warfarin costs a few dollars for a 30-day supply, its cost approaches that of the other anticoagulants when visits to a physician for monitoring are factored in, Dr. Hallstrom said. In contrast, aspirin costs approximately $2 a month.
The study suggests most patients can have just aspirin without increasing the risk for VTE, but surgeons need to consider factors such as a patient’s history of VTE, obesity, and ability to mobilize after surgery when determining the best measure for VTE prophylaxis, Dr. Hallstrom said.
Hood BR, Cowen ME, Zheng HT, Hughes RE, Singal B, Hallstrom BR. Association of aspirin with prevention of venous thromboembolism in patients after total knee arthroplasty compared with other anticoagulants: a noninferiority analysis. JAMA Surg. 2018 Oct 17. doi: 10.1001/jamasurg.2018.3858. [Epub ahead of print]