In the present study, only a quarter of patients had good TTR. Higher education level is the independent predictor of better TTR. The HRQoL of these patients was moderate, but their treatment satisfaction was good. The HRQoL and treatment satisfaction was similar irrespective of patients’ TTR. The only exception was patients with good TTR tends to have a better social functioning. Nearly one-fifth of patients had been hospitalised for bleeding tendency. Hospitalisations and bleeding tendency were independent of patients’ TTR.
Existing studies concluded patients from western countries had better TTR than their Asian counterpart. The International Study of Anticoagulant Management (INSAM) was a retrospective analysis of the real-world patients receiving warfarin for NVAF in five western countries, namely the United State, Canada, France, Italy and Spain.(25) The reported mean TTR was 57.0% – 68.9%, while the proportion of patients with good TTR (≥ 60%) was 47.7% − 75.1%. The Global Anticoagulant Registry in the Field (GARFIELD) AF reported an overall mean TTR of 55.4% and overall good TTR (≥ 65%) of 41.1% among their patients.(18) The subgroup analysis however demonstrated only 16.7% of Asian cohort had good TTR compare to 49.4% of European cohort. In another study by Chan et al, Hong Kong patients on warfarin for NVAF were reported to have a mean TTR of 38.8% and good TTR (≥ 65%) of 14.8%.(26) Oh et al reported only 27% of Korean on warfarin for NVAF had good TTR (≥ 60%).(27) Therefore, the lower mean TTR and the fewer good TTR among patients in this study were similar to other Asia studies. The possible explanations for this variation include Asian may have different diet and genetic, such as polymorphisms of VKOR1 and CYP2C9 genes.(11, 12, 28) The INSAM study and a meta-analysis by van Walraven et al reported the clinical setting of warfarin given was the strongest predictor of patients TTR, being highest in randomised control trials, followed by anticoagulant clinic and community practise.(25, 29) The present study further added low education level was associated with a poorer TTR.
To date, there is no published data that compares the HRQoL of adult patients on warfarin for NVAF based on their TTR. Most of the existing studies either compare the HRQoL of these patients versus those on DOAC, or in a longitudinal manner. Ng et al,(30) Benzimra et al,(31) Contreras et al,(32) and Alegret et al,(33) have reported no significant difference in the HRQoL of patients with NVAF receiving long-term warfarin versus DOAC in real-world scenario. On the other hand, Balci et al reported significant improvement in every domain of SF-12v2 (all p < 0.001),(34) while de Caterina et al reported significant improvement in severe mobility problem (p = 0.003), pain/discomfort (p = 0.035), and anxiety/depression (p < 0.001) of EuroQoL Instrument 5 levels (EQ-5D-5L) among NVAF patients after switching from warfarin to DOAC.(35) The patients in the current study had slightly higher value in each domain of the SF-12v2 except SF, but much lower mean TTR (47.0% versus 54.9%) and proportion with good TTR (24.3% versus 45.0%) when compared to similar subgroup of patients reported in Ng et al.(30) Both studies were conducted in the anticoagulant clinic of a tertiary hospital, but the latter located in the Peninsular of Malaysia. The better social functioning among patients with good TTR in the current study could be due to their higher education level.
In this study, the finding of treatment satisfaction was independent of patients’ TTR was consistent with that reported in previous study. In the Outcome Registry for Better Informed Treatment of AF (ORBIT-AF) study, the treatment satisfaction of patients on warfarin for AF evaluated by using Anti-Clot Treatment scale (ACTS) was not affected by the TTR.(36) Similar finding was also observed in the Korean patients who received warfarin for NVAF when assessed by the Treatment Satisfaction Questionnaire for Medication (TSQM).(27) A post-hoc study (ALADIN and ESPARTA) however reported significantly higher ACTS burden scale (better satisfaction) in NVAF patients with good TTR (≥ 50%) (p = 0.024).(37) The cut-off point of good TTR in this study was lower than that commonly used (60% − 65%), therefore unable to make direct comparison with the current study.
The current study concludes that majority of the NVAF patients attending SHC had poor anticoagulant control, which may be attributed to lower education level. We recommend patients with poor TTR should be reassured that achieving a good TTR confers a better clinical outcome but does not compromise their HRQoL or satisfaction. These patients may benefit from frequent education on anticoagulant by clinicians and pharmacists during their follow-up appointments. Furthermore, the implementation of warfarin medication therapy adherence clinic (WMTAC) protocol may also help to improve patinets’ INR control.(38) Switching from warfarin to DOAC should be consider in NVAF patients with poor TTR in view of the better efficacy, HRQoL and treatment satisfaction, as well as lesser side-effects. In area where the poor INR control among NVAF patients is common, DOAC should be consider as the first-line anticoagulant.
To our knowledge, this is the first study that compares the HRQoL of NVAF patients on long-term warfarin based on their TTR. Analysis of each domain of the SF12v2 and each item of the DASS were performed in order to provide a more detailed comparison. The analyses of HRQoL and treatment satisfaction were adjusted for age and treatment duration as cofounders to minimise the result bias. This study had several limitations. Firstly, it was performed in a single centre, thus limiting the generalisability of the results. Secondly, the cross-sectional design might not be able to completely reflect the HRQoL, as HRQoL may vary over time. Thirdly, the patients HAS-BLED score and severity of bleeding was not assessed. Most of the patients were unable to remember their non-clinical significant minor bleed episode. Fourthly, patients with vascular disease taking anti-platelet were excluded. Finally, the treatment complications were subject to the recall bias of patients, but this was minimised by double checking available medical records.