Assessment of anticoagulation knowledge and adherence in patients with atrial fibrillation (2023)

Atrial fibrillation (AF) is the most common arrhythmia encountered in clinical practice, and is responsible for 20-30% of all strokes. AF-related strokes are more severe, and result in longer hospital stays and higher mortality compared to non-AF-related strokes. In Australia, the prevalence of AF is 5.35% in individuals aged 55 years and older, and it is associated with a cost of at least AUD$1.25 billion per year, resulting largely from the incidence of stroke, heart failure and premature mortality. Oral anticoagulant (OAC) therapy is highly effective for stroke prevention in patients with AF; however, it is also associated with the potential risk of bleeding. Evidence from clinical trials demonstrates that OAC therapy reduces the risk of stroke by 64% to 70%, and is associated with a rate of major bleeding events of up to 3.6% per year. For optimal benefit to be derived from OAC therapy, patients are required to adhere to the prescribed regimen and have sufficient knowledge regarding their medication. Various studies have demonstrated associations between suboptimal adherence and inadequate knowledge regarding OAC therapy with poor treatment outcomes. Suboptimal adherence to OAC therapy has been associated with increased risks of both bleeding and embolic events, while inadequate knowledge has been associated with poor anticoagulation control, which in turn is associated with poorer clinical outcomes. This suggests that OAC knowledge and adherence are important concepts to be considered in high quality management of patients with AF. Assessment of medication knowledge in routine clinical practice requires the use of validated psychometric instruments. The majority of studies conducted in patients with AF have utilised instruments of unknown validity to evaluate OAC knowledge. This makes it difficult to ascertain whether OAC knowledge has been appropriately assessed. In the last decade, the Anticoagulant Knowledge Assessment (AKA) by Briggs et al and the Oral Anticoagulant Knowledge test (OAK) by Zeolla et al were developed and validated to assess OAC knowledge. However, both the OAK and AKA are only able to assess knowledge related to the use of vitamin K antagonists (VKAs), and are not applicable to the direct-acting oral anticoagulants (DOACs). An instrument that caters for both patients taking VKAs and DOACs would be useful in clinical practice to identify knowledge deficit in patients with AF, and to guide subsequent educational intervention. Additionally, there is a lack of contemporary data regarding OAC knowledge level and the rate of non-adherence to OAC therapy in Australia, and their relationship with patient-related factors. Contemporary data are necessary to assess the adequacy of OAC knowledge in the population, and address any deficiencies or misconceptions. Furthermore, contemporary data are needed to identify the barriers to OAC adherence, and identify relevant predictors of non-adherence in the population. Studies related to OAC knowledge and adherence that have been conducted in Australia to date have focused primarily on participants taking VKAs (warfarin). Given the increased rate of prescription of DOACs, as well as switching of patients previously taking warfarin to DOACs, recent data on OAC therapy would be useful in evaluating the impact of DOAC prescribing on patients' knowledge level and adherence to therapy. Accordingly, the development of this thesis was guided by the Capability, Opportunity and Motivation Model of Behaviour (COM-B), which hypothesises that interaction between three components, Capability, Opportunity and Motivation (COM), influence the performance of Behaviour (B). Factors related to each of the three components were explored as they influence OAC adherence. Therefore, the overall objective of this research was to fill these gaps by developing an instrument that caters for all OACs, and assessing OAC knowledge and adherence in patients with AF. The specific aims were: ‚Äö To develop and validate a new OAC knowledge instrument that caters for both VKAs (warfarin) and the DOACs. ‚Äö To use this instrument, the Anticoagulation Knowledge Tool (AKT), to investigate the relationships between OAC knowledge, adherence and health literacy in patients with AF. ‚Äö To determine the level of OAC knowledge in patients with AF taking OAC therapy (either warfarin or a DOAC), identify any domains where significant knowledge gaps exist, and assess the association between patient-related factors and OAC knowledge. ‚Äö To estimate the proportion of patients who are non-adherent to OAC and identify predictors of adherence, and to determine if patient-related factors vary across levels of adherence in patients with AF. Due to the absence of a suitable instrument to assess OAC knowledge, we began this research by conducting a comprehensive review of the literature on anticoagulation knowledge, from which a draft instrument was developed. Ten anticoagulation experts were contacted to provide feedback on the draft instrument using a Likert scale, after which the content validity index for the instrument was calculated. For construct validity, three groups of participants comprising of 44 pharmacists, 50 patients and 50 members of the general public were tested using the instrument developed, and the results of these three cohorts were compared. Reliability analyses were conducted to determine if included items were measuring the same general construct, and if the instrument could provide consistent results. A subgroup of participants in the patient and pharmacist groups were re-tested approximately 2‚Äö-3 months after the initial testing to assess test retest reliability using Pearson's correlation coefficient, while internal consistency reliability was assessed by calculating a Cronbach's ˜í¬± value for the three groups. The final 28-item instrument, called the AKT, has a scale content validity index of 0.92, supporting content validity. The pharmacist group's mean score (94%) was significantly higher than that of the patient group (62%), and the patient group scored significantly higher than the general public group (20%) (p <0.001), supporting construct validity. Internal consistency reliability was acceptable with a Cronbach's ˜í¬± value of >0.7 across the three groups, and test-retest reliability was confirmed with a Pearson's correlation coefficient of 0.72 and 0.78 for the pharmacist and patient groups, respectively. After the development of the AKT, the instrument was piloted in a study involving 48 patients designed to investigate the relationships between OAC knowledge, adherence and health literacy in patients with AF. Participants were recruited from general practices for a face-to-face interview using the AKT to assess OAC knowledge; the Morisky Medication Adherence Scale (MMAS-8) to assess adherence; and the Short Test of Functional Health Literacy in Adults (s-TOFHLA) to assess health literacy. Participants had mean scores of 61.6 ¬¨¬± 15.8, 7.2 ¬¨¬± 1.1 and 24.7 ¬¨¬± 9.5 for the AKT, MMAS-8 and s-TOFHLA, respectively. Significant correlations were observed between OAC knowledge and health literacy with medication adherence (0.37, p = 0.009 and 0.30, p = 0.042, respectively), and between OAC knowledge and health literacy (0.31, p = 0.033). Participants with inadequate health literacy had a significantly lower mean knowledge score than those with adequate health literacy (55.8 ¬¨¬± 15.9 versus 66.1 ¬¨¬± 14.4, p = 0.022). In addition, participants who reported adequate adherence to OAC therapy had significantly higher knowledge scores than those who did not (67.5 ¬¨¬± 13.3 versus 56.1 ¬¨¬± 16.2, p = 0.011). After confirming the usability and adequacy of the AKT, the next phase of this research focused on assessing OAC knowledge and adherence in patients with AF in a nationally representative sample of patients with AF. The study was designed as an online survey to improve reachability and ensure better representation. Survey components used included the AKT, the Perception of Anticoagulant Treatment Questionnaires (assessing treatment expectations, convenience and satisfaction), a modified Cancer Information Overload scale to assess perception of information overload, and the MMAS-8 to assess OAC adherence. Although participants taking warfarin had a higher knowledge score compared to those taking DOACs (n = 386, 73.4 ¬¨¬± 13.2 versus 65.7 ¬¨¬± 13.7, p <0.001), knowledge gaps were generally observed in key areas of self-management including the following: missing a dose, drug interactions and recognising bleeding as an important side effect. Patient-related factors including age in years (p = 0.009) and perception of information overload (p <.001) were significant predictors of knowledge. To estimate the proportion of patients who were non-adherent to OAC therapy, and identify factors associated with adherence in the population, a secondary analysis of the data was conducted. Nonadherence to OAC therapy was common, as only 54.9% of participants reported a high adherence to OAC. Participants aged ‚Äöv¢¬ß65 years were less likely to have high adherence compared to older participants (OR, 0.54; 95% CI, 0.33 ‚Äö- 0.88; p = 0.013), while females were more likely to be highly adherent compared to males (OR, 1.69; 95% CI, 1.08 ‚Äö- 2.64; p = 0.023). Moreover, the result of the secondary analysis showed that treatment satisfaction (p <0.001) and perception of information overload (p <0.001) varied across adherence levels. Mapping the results from this research to the COM-B framework suggests that each of the components could be explored to improve OAC adherence. Improving knowledge and health literacy levels may increase patients' psychological capability to engage in the necessary thought process that would encourage adherence to OACs. Potentially, healthcare practitioners could use the results of this research to help shape patients' perception and beliefs concerning OAC th...

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