Warfarin tablets
WASHINGTON, DC—An analysis of real-world data suggests elderly patients with non-valvular atrial fibrillation (NVAF) have a lower risk of stroke or systemic embolism and a lower risk of major bleeding if they receive apixaban rather than warfarin.
The study also indicates that elderly NVAF patients who receive dabigatran have a similar risk of stroke/systemic embolism as those on warfarin, but the risk of major bleeding is lower with dabigatran.
And rivaroxaban poses a lower risk of stroke/systemic embolism than warfarin but a higher risk of major bleeding.
However, the researchers who conducted this analysis stressed that it cannot be used as stand-alone evidence to validate the efficacy and/or safety of any of the drugs studied.
The results of the analysis were presented at the American College of Cardiology’s 66th Annual Scientific Session (abstract 1134M-13).
The researchers also presented data on the financial costs of major bleeding associated with apixaban, dabigatran, rivaroxaban, and warfarin (abstract 1189-085/085).
The research was conducted by employees from Bristol-Myers Squibb Company and Pfizer Inc., the companies marketing apixaban, as well as other researchers who have relationships with the companies.
The team evaluated medical and pharmacy claims from the US Medicare fee-for-service database. They looked at NVAF patients age 65 and older who were newly prescribed apixaban, dabigatran, rivaroxaban, or warfarin between January 1, 2013, and December 31, 2014.
The researchers compared each of the direct oral anticoagulants to warfarin using 1:1 propensity score matching methodology to balance select demographic and clinical characteristics between the groups.
The team used Cox proportional hazards models to estimate the hazard ratio (HR) of stroke/systemic embolism and major bleeding.
Results
In a comparison of apixaban and warfarin (20,803 patients in each treatment group), apixaban was associated with a significantly lower risk of stroke or systemic embolism than warfarin (HR: 0.40, 95% CI: 0.31-0.53; P<0.0001).
Apixaban was also associated with a significantly lower risk of major bleeding than warfarin (HR: 0.51, 95% CI: 0.44-0.58; P<0.0001). The cost of major bleeding per patient per month was $286 with apixaban and $537 with warfarin (P<0.0001).
In a comparison of dabigatran and warfarin (16,731 patients in each treatment group), the risk of stroke or systemic embolism was similar between the cohorts (HR: 0.94, 95% CI: 0.74-1.21; P=0.647).
However, the risk of major bleeding was significantly lower with dabigatran than with warfarin (HR: 0.79, 95% CI: 0.69-0.91; P=0.001). The cost of major bleeding per patient per month was $367 with dabigatran and $452 with warfarin (P=0.032).
In a comparison of rivaroxaban and warfarin (52,476 patients in each group), rivaroxaban was associated with a significantly lower risk of stroke or systemic embolism than warfarin (HR: 0.72, 95% CI: 0.63-0.83; P<0.0001).
However, the risk of major bleeding was significantly higher with rivaroxaban than with warfarin (HR: 1.17, 95% CI: 1.10-1.26; P<0.0001). The cost of major bleeding per patient per month was $524 with rivaroxaban and $500 with warfarin (P=0.154).
Limitations
The researchers noted that this analysis has several limitations. For instance, information on laboratory results and time in therapeutic range were not available. Diagnoses were identified through ICD-9 codes, and drug prescriptions were identified through prescription claims.
Propensity score matching was used to mimic randomization by balancing pre-defined demographic and clinical characteristics at baseline for both treatment cohorts. However, unobserved confounders (such as laboratory values and patient preferences) may exist.
As with any real-world data analysis, missing values, coding errors, and a lack of clinical accuracy may have introduced bias.
The researchers stressed that, due to such limitations, real-world data analyses cannot be used as stand-alone evidence to validate the efficacy and/or safety of a treatment. However, these analyses add to information provided by randomized clinical trials.
“Studies such as this large US Medicare database analysis supplement pivotal trials by broadening and deepening our scientific knowledge of how patients respond to direct oral anticoagulants in everyday clinical practice,” said Alpesh Amin, MD, principal investigator and professor of medicine at the University of California, Irvine.
“Given the diversity of patients with non-valvular atrial fibrillation, analyses of real-world data provide further information that adds to data generated in randomized clinical trials.”
