Discussion
The analyses of this large and nationally representative data suggest
changing practice trends in the rate and type of OAC prescribing over
the last ten years. The proportion of patients with moderate to high
stroke risk who were prescribed an OAC increased steadily by one-third
from 2009-2018. This increase in the proportion patients with moderate
to high stroke risk who were prescribed an OAC was significantly higher
from 2013 onwards, corresponding with the PBS listing of DOACs for
Australian government subsidisation (rivaroxaban in August 2013, and
apixaban and dabigatran in September 2013) (Drug Utilisation
Sub-Committee (DUSC), June 2016). In 2010, the European Society of
Cardiology (ESC) guidelines recommended prescribing of an OAC for all AF
patients at moderate-high risk of stroke (i.e.,
CHA2DS2-VASc score ≥1) instead of
antiplatelet therapy (Camm et al., 2010). This was followed by the 2012
ESC’s updated recommendation to avoid prescribing of aspirin in
low-stroke risk patients (Camm et al., 2012). These changes may also
explain the surge in OAC prescribing during the study period (Camm et
al., 2012). Similar trends of an increase in OAC use, with a slow
initial uptake after the introduction of DOACs, have been reported by
studies from the United Kingdom and Denmark (Gadsboll et al., 2017; Loo,
Dell’Aniello, Huiart & Renoux, 2017).
In 2018, just over half of the high-risk patients were prescribed an
OAC. This rate is low compared with the rates reported from previous
studies. The Tasmanian AF study found 63% of high-risk patients were
prescribed an OAC. However, that study involved hospitalised patients
who might have been more comorbid than general practice patients and it
excluded patients with known OAC contraindications. A study in the UK
using general practice data found that over three-quarters of high-risk
patients with AF were prescribed an OAC (Adderley, Ryan, Nirantharakumar
& Marshall, 2018). Another study from Denmark found that two-thirds of
patients were prescribed an OAC (Gadsboll et al., 2017).
Despite an overall increase in OAC prescribing over the study period,
there remained wide gaps between the highest- and lowest-performing
practices in both appropriate (for moderate to high stroke risk) and
potentially inappropriate (for low stroke risk) prescribing, which
increased over time. One possible reason for the observed gaps in the
appropriate use of an OAC might be the absence of regular reassessment
of CHA2DS2-VASc scores. A study by Yoon
et al. (Yoon et al., 2018) found that 46.6% of low-risk and 72% of
moderate-risk patients at baseline were reclassified as being at high
stroke risk within 10 years of follow-up. Increasing general
practitioners’ awareness of the need for annual stroke risk assessment
may improve OAC prescribing.