NOAC Adherence of Patients with Atrial Fibrillation in the Real World: Dosing Frequency
Matters?
In 2019, 10 years have been passed since the introduction of dabigatran to the market
with the specific indication of managing thromboembolic risk in atrial fibrillation
(AF) patients.[1] Since then, three other nonvitamin K antagonist oral anticoagulants (NOACs) have
been introduced and NOACs have become increasingly popular for stroke prevention in
patients with AF.[2] One of the advantages of NOACs over vitamin K antagonists (VKAs) is the absence
of continuous monitoring of the international normalized ratio (INR).[3] Indeed, while using VKA obtaining and maintaining an optimal quality of anticoagulation
therapy control is essential to achieve a significant protection from thromboembolic
events and mortality, without increasing bleeding risk.[4] However, adherence and persistence to oral anticoagulation for some patients is
problematic and this requires efforts to improve appropriate prescriptions, to monitor
NOAC adherence and implement strategies to improve adherence where it is found to
be suboptimal.[3]
[5] For anticoagulation clinics, obtaining good INR control and time in the therapeutic
range is the major objective of the clinical management. With less need for monitoring
with NOACs, those patients who do not follow the prescribed regimen are likely to
experience poorer adherence, and this may not be captured as adherence and may not
be routinely assessed.[6]
In a recent narrative review, we reported how the rate of adherence and persistence
in NOACs users ranged widely across studies, with varying settings and patients typology[6] and demonstrated how both adherence and persistence declined over time.[6]
In the previous issue of Thrombosis and Haemostasis, Hwang et al explored the issue of NOACs adherence in a cohort of real-life AF patients
enrolled in a single Korean tertiary referral cardiology department.[7] They evaluated the adherence to treatment, expressed as percentage of prescribed
doses taken (PDT), and also evaluated adherence with the Morisky Medication Adherence
Scale (MMAS)-8 tool. In a cohort of 719 AF patients prescribed one of the four NOACs
(apixaban 47.8%, dabigatran 21.2%, rivaroxaban 18.4%, and edoxaban 12.6%), they found
that over a mean (standard deviation [SD]) treatment period of 7.2 (5.7) months, the
mean (SD) PDT for the once-daily NOACs (rivaroxaban and edoxaban) was 95.4 (9.1%)
and 93.4% (12.7%) for the twice-daily NOACs (dabigatran and apixaban). Overall, 92.2%
of patients reported high adherence (PDT ≥ 80%). Among the various NOACs, use of dabigatran
was associated with the lowest adherence (PDT = 89.8%), while in general the twice-daily
dosing was associated with an increased risk of reporting poorer adherence (PDT < 80%)
in the univariate analysis (odds ratio [OR]: 2.15; 95% confidence interval [CI]: 1.06–4.34).
A sensitivity analysis performed excluding dabigatran users found that twice-daily
dosing no longer affected adherence.[7]
The MMAS-8 was a good predictor of poor adherence, showing an AUC of 0.751 (p < 0.001), with a MMAS-8 ≥3 exhibiting a 63.8% sensitivity and 78.5% specificity for
poor adherence. In a multivariate logistic regression analysis, the twice-daily NOAC
regimen was independently associated with a MMAS score of ≥3 (OR: 1.90; 95% CI: 1.35–2.67).[7]
The data presented appear reassuring in terms of good adherence with NOAC in this
cohort, with less than 10% of patients reporting a PDT <80%. However, the study does
have some limitations, namely one Korean center only, relatively small cohort managed
exclusively in a tertiary center with a limited follow-up period, which may impact
the generalizability of the results.
A recent study performed among the UK primary electronic health records system (The
Health Information Network), reports more concerning figures regarding OAC adherence.
In this analysis, good adherence was defined as the proportion of days covered (PDC)
of >80%. Good adherence among users of oral anticoagulant drugs was 55.2% overall,
being lowest in VKA users (51.2%) and significantly higher in NOACs users (dabigatran
66.5%, rivaroxaban 63.1%, and apixaban 64.7%)[8] but still far from optimal. This study also showed that the rate of good adherence
was lower in those patients with a shorter follow-up available. Previous data were
similar indicating that over time the adherence rate was progressively lower, irrespective
of the type of NOACs used.[6]
The paper by Hwang et al addresses an important issue regarding OAC management, that
of adherence. Indeed, the ability of MMAS-8 to predict the occurrence of a poor adherence
is useful in terms of clinical management of these patients and could be utilized
alongside other tools to evaluate AF patients. Indeed, the SAMe-TT2R2 score has been designed to identify those AF patients that would more likely perform
well if prescribed with VKA,[9]
[10]
[11] which is relevant since VKAs are still widely used OAC globally.
Despite all international guidelines currently recommending the use of NOACs over
VKA for the majority of AF patients,[12]
[13] optimal management of these patients should evaluate the most appropriate oral anticoagulant
as part of an integrated care approach for AF patients.[14]
[15]
[16] During the baseline evaluation of AF patients, use of MMAS-8 could help to identify
those patients that more likely will have a poor adherence to treatment and could
be used to plan specific interventions to improve adherence.
Many factors are implicated in adherence to oral anticoagulant therapy among the patient-related
factors are demographics, medical-related, behavioral factors, and patient understanding.[6] Although many strategies to address nonadherence have been proposed,[6] these need to be individually tailored to the patient based on the personal underlying
cause(s) of non-adherence. Improving adherence to OAC in AF patients should be a priority
of the clinical management of AF since data indicate that patients more adherent to
NOACs are more likely to have better outcomes.[17] Starting anticoagulation is not enough, we need to ensure that patients are adherent
lifelong by asking about medication adherence and where non-adherence is identified,
working with the patient to develop strategies to improve adherence and ensuring these
are implemented and maintained ([Fig. 1]).
Fig. 1 Relationship between oral anticoagulant treatment, adherence, and outcomes in atrial
fibrillation patients.
