Objectives

• Assess the adherence to treatment with conventional measures of primary and secondary adherence in routine clinical practice
• Describe adherence trajectories or patterns (trajectory models or latent class growth analysis models)
• Estimate the factors associated with these trajectories.
• Assess the impact in terms of clinical results of effectiveness and safety.

State

Adherence to oral anticoagulants in patients with atrial fibrillation—a population-based retrospective cohort study linking health information systems in the Valencia region, Spain: a study protocol.

• Adherence to oral anticoagulation (OAC) treatment, vitamin K antagonists or new oral anticoagulants, is an essential element for effectiveness. Information on adherence to OAC in atrial fibrillation (AF) and the impact of adherence on clinical outcomes using real-world data barely exists. We aim to describe the patterns of adherence to OAC over time in patients with AF, estimate the associated factors and their impact on clinical events, and assess the same issues with conventional measures of primary and secondary adherence—proportion of days covered (PDC) and persistence—in routine clinical practice.

Real-world adherence to oral anticoagulants in atrial fibrillation patients: a study protocol for a systematic review and meta-analysis

• Atrial fibrillation (AF) is one of the leading causes of cerebrovascular mortality and morbidity. Oral anticoagulants (OACs) have been shown to reduce the incidence of cardioembolic stroke in patients with AF, adherence to treatment being an essential element for their effectiveness. Since the release of the first non-vitamin K antagonist oral anticoagulant, several observational studies have been carried out to estimate OAC adherence in the real world using pharmacy claim databases or AF registers. This systematic review aims to describe secondary adherence to OACs, to compare adherence between OACs and to analyse potential biases in OAC secondary adherence studies using databases.

Primary Nonadherence to Oral Anticoagulants in Patients with Atrial Fibrillation: Real-World Data from a Population-Based Cohort.

• Primary nonadherence (not filling a first prescription) is an important yet unstudied aspect of adherence to oral anticoagulant (OAC) therapy.
   
• Results: Primary nonadherence to OACs was 5.62% (VKA 4.29% vs. NOAC 10.81%; P < 0.001), with varying rates among specific drugs (acenocoumarol 4.2%, warfarin 10.9%, apixaban 5.0%, dabigatran 7.9%, and rivaroxaban 15.5%). After adjusting for potential confounders, the likelihood of not filling the first prescription was higher for NOAC patients than for VKA patients (OR = 2.76, 95% CI = 2.41-3.15). High coinsurance in the older groups (OR = 2.63, 95% CI = 1.47-4.69 for patients aged 66-75 years and OR = 3.02, 95% CI = 1.58-5.76 for patients aged > 75 years); being a non-Spanish European (OR = 1.49, 95% CI = 1.12-1.99); and having dementia (OR = 1.72, 95% CI = 1.37-2.16) were positively associated with primary nonadherence. Electronic transmission of prescriptions (OR = 0.85, 95% CI = 0.74-0.96); liver disease (OR = 0.73, 95% CI = 0.54-0.99); and polypharmacy (OR = 0.59, 95% CI = 0.50-0.70) were inversely associated with primary nonadherence.
   
• Conclusions: Overall, primary nonadherence to OACs was relatively low (5%). However, important differences were found between VKAs and NOACs. After adjustment, patients prescribed NOACs nearly tripled the likelihood of nonadherence compared with patients prescribed VKAs, which could negatively affect their effectiveness in clinical practice. Identified correlates were similar to those shown in the limited evidence for other medications.

Estimating Adherence Based on Prescription or Dispensation Information: Impact on Thresholds and Outcomes. A Real-World Study With Atrial Fibrillation Patients Treated With Oral Anticoagulants in Spain

• To estimate drug exposure, Proportion of Days Covered (PDC) and percentage of patients with PDC ≥ 80% from a cohort of atrial fibrillation patients initiating oral anticoagulant (OAC) treatment. We employed three different approaches to estimate PDC, using either data from prescription and dispensing (PD cohort) or two common designs based on dispensing information only, requiring at least one (D1) or at least two (D2) refills for inclusion in the cohorts. Finally, we assessed the impact of adherence on health outcomes according to each method.
   
• Results: PD cohort included all patients with an OAC prescription (n = 38,802), D1 cohort excluded fully non-adherent patients (n = 265) and D2 cohort also excluded patients without two refills separated by 180 days (n = 2,614). PDC ≥ 80% ranged from 94% in the PD cohort to 75% in the D1 cohort. Drug exposure among adherent (PDC ≥ 80%) and non-adherent (PDC < 80%) patients was different between cohorts. In adjusted analysis, high adherence was associated with a reduced risk of death [Hazard Ratio (HR): from 0.82 to 0.86] and (except in the PD cohort) the risk for ischemic stroke (HR: from 0.61 to 0.64) without increasing the risk of bleeding.
   
• Conclusions: Common approaches to assess adherence using measures based on days’ supply exclude groups of non-adherent patients and, also, misattribute periods of doctors’ discontinuation to patient non-adherence, misestimating adherence overall. Physician-initiated discontinuation is a major contributor to reduced OAC exposure. When using the PDC80 threshold, very different groups of patients may be classified as adherent or non-adherent depending on the method used for the calculation of days’ supply measures. High adherence and high exposure to OAC treatment in NVAF patients is associated with better health outcomes.

Funding