Study: Adherence Rates Among Patients With AF Who Began Anticoagulation Therapy

Of patients who began anticoagulation therapy in the first year after atrial fibrillation (AF) diagnosis, 40% who initiated warfarin therapy and 47% of those who initiated DOAC treatment did not continuously adhere to therapy.  

According to a team of researchers, who published their study findings online in JAMA Network Open, AF impacts 2.3 million patients in the United States and is the most common cardiac arrhythmia in older adults. Additionally, the researchers said that oral anticoagulant (OAC) therapy is linked with a reduced risk of stroke that is associated with AF by roughly 60%. However, OAC treatment is also linked with an increased bleeding risk.  

“Clinical guidelines recommend the use of OAC therapy for patients with a moderate or high risk of stroke, which is generally defined as having a CHA₂DS₂-VASc (cardiac failure or dysfunction, hypertension, age 65-74 [1 point] or ≥75 years [2 points], diabetes, and stroke, transient ischemic attack or thromboembolism [2 points]–vascular disease, and sex category [female]) risk score of 2 or more,” the authors explained. “In spite of the important role of OAC therapy in stroke prevention, only 50% to 60% of US patients with AF recommended for OAC therapy actually receive these medications, and less than half of them adhere to them over time.”  

Among those who do receive OAC therapy, researchers were curious about the following question: “What are the longitudinal patterns of adherence to treatment with warfarin and direct oral anticoagulants among patients with atrial fibrillation who initiate anticoagulation therapy?”  

In order to answer this question, a retrospective cohort study using 2013 to 2016 Medicare claims data was conducted. The research team identified 7491patients (4348 women; mean (SD) age was 76.0 (10.0) years) with a new diagnosis of AF in 2014 to 2015 who initiated warfarin after AF diagnosis. Additionally, they identified 9478 patients (5496 mean (SD) age was 77.0 (8.5) years) with a new diagnosis of AF in 2014 to 2015 who initiated DOAC treatment after AF diagnosis. In total, the researchers identified a total of 16,969 Medicare beneficiaries. 

“The main outcome was the proportion of days that patients received warfarin or DOAC, measured in 30-day intervals after AF diagnosis,” study authors noted.  

The researchers identified the following four latent classes of patients based on warfarin adherence: late initiators (980 [13%]); early initiators who discontinued therapy at months 1 to 3 (1297 [17%]) or at months 5 to 10 (735 [10%]); and continuously adherent patients (4479 [60%]). Among patients on DOAC adherence, the following four latent classes were also identified: patients who initiated DOAC in months 1 to 5 (1368 [14%]) or months 6 to 11 (800 [8%]); patients with suboptimal and decreasing adherence (2267 [24%]); and continuously adherent patients (5043 [53%]).  

According to the findings, membership in latent classes of warfarin adherence was associated with the following: 

• sex;
• eligibility for Medicaid and income subsidy;
• region of residence;
• CHA₂DS₂-VASc risk score; and
• HAS-BLED (hypertension, abnormal renal and liver function, stroke, bleeding, labile international normalized ratio, elderly, and drugs or alcohol) score.

Additional findings showed that race/ethnicity, region of residence, HAS-BLED score, and use of antiarrhythmic medications were associated with membership in latent classes of DOAC adherence.  

“This study found that, among patients who initiated anticoagulation therapy, 40% of those who initiated warfarin therapy and 47% of those who initiated DOAC treatment did not continuously adhere to therapy in the first year after AF diagnosis,” the study authors concluded.  

“Identifying longitudinal patterns of warfarin and DOAC adherence and the factors associated with them provides suggestions for the design of targeted strategies to mitigate suboptimal oral anticoagulation use.” 

—Julie Gould

Reference:

Chen N, Brooks MM, Hernandez I. Latent classes of adherence to oral anticoagulation therapy among patients with a new diagnosis of atrial fibrillation [published online February 19, 2020]. JAMA Netw Open. 2020;3(2):e1921357. doi:10.1001/jamanetworkopen.2019.21357