Patients taking prescribed antiplatelet medication for preexisting conditions (~20% of patients in each group) were allowed to continue antiplatelet therapy during the trial. Patients were excluded if they were receiving an anticoagulant prior to their procedure or had a medical contraindication to aspirin or enoxaparin.
Thirty-one hospital sites were randomly assigned a treatment protocol using either aspirin or enoxaparin. Once target patient enrollment was met with the initial assigned medication, the site switched to the second/other agent. This resulted in 5675 patients in the aspirin group and 4036 in the enoxaparin group enrolled between April 2019 and December 2020, with final follow-up in August 2021; of these, 259 in the aspirin group and 249 in the enoxaparin group were lost to follow-up, opted out, or died.
The aspirin group was given 100 mg PO daily and the enoxaparin group was given 40 mg SC daily (20 mg daily for patients weighing < 50 kg or with an estimated glomerular filtration rate < 30 mL/min/1.73 m2) for 35 days after THA and 14 days after TKA. Both treatment groups received IPC calf devices intraoperatively and postoperatively, and mobilization was offered on postoperative Day 0 or 1.
The primary outcome—development of symptomatic VTE within 90 days of the procedure—occurred in 187 (3.5%) patients in the aspirin group and 69 (1.8%) patients in the enoxaparin group (estimated difference = 1.97%; 95% CI, 0.54%-3.41%). This did not meet the noninferiority criterion for aspirin, based on an estimated assumed rate of 2% and a noninferiority margin of 1%, and in fact was statistically superior for enoxaparin (P = .007). There were no significant differences between the 2 groups in major bleeding or death within 90 days.1
WHAT’S NEW
Enoxaparin was significantly superior to aspirin for VTE prophylaxis
Although this study was designed as a noninferiority trial, analysis showed enoxaparin to be significantly superior for postoperative VTE prophylaxis compared with aspirin.
Continue to: CAVEATS
