Data from Antithrombosis News - Curated by EPG Health - Last updated 31 October 2018

Today’s Cardiovascular epidemiology session included the study, National prescribing and adverse event rates of patients at risk of stroke with non-valvular AF from CPRD linked database: does 'big data' reflect clinical trials and identify areas for improvement?

We know patients with a CHADSVASC score of >/=1 should be prescribed anticoagulation (with consideration of the bleeding risk) as per ESC and NICE guidelines. This study retrospectively evaluated prescription data using primary care databases, alongside hospital episode statistics to evaluate adverse event rates for patients in different treatment groups and compared real-world data to seminal trials looking at anticoagulation in stroke prevention.

The stated aims were:

  1. Establish what influenced a primary care clinician’s choice of AF treatment 
  2. Link this data with hospital episode statistics to establish adverse event rates and identify potentially at-risk populations
  3. Compare adverse event rates in a real-world dataset to key clinical trial groups

Just under 43,000 patients over a 5-year period were identified with a new diagnosis of NVAF. Of these, 13,405 started on a single treatment regimen for at least 3 consecutive months – 15% on NOACs, 42% on warfarin, 38% on aspirin, and 5% on other treatments.  9,148 patients were not given any treatment.  

The histograms in Figure 1, below show a relatively consistent distribution of CHA2DS2-VASc and HAS-BLED scores between treatment groups, suggesting risk of ischaemic stroke and major bleed were similar between treatment groups.  However, as patient age increases, anticoagulation prescribing decreases. Particularly in frail patients. 

Table 1 shows adverse event rates per treatment group.  As expected, there were similar adverse event rates for NOACs and warfarin.  However, patients outside these groups have significantly worse outcomes.  

Incidence of ischaemic stroke increases as you move away from anticoagulation.  Particularly marked results identify the incidence of ischaemic stroke in the No treatment group, being almost 5 times as high as the Anticoagulant group, with resultant mortality markedly higher. In the Antiplatelet group, risk is twice as high.  Figure 1 histograms show frail and older patients are likely to be part of the Undertreated group.

Finally, clinical trial groups and these real-world datasets identified similar adverse event rates.  However, all-cause mortality was much higher in the real-world dataset: 18.7 vs 42.8 for the NOAC group.  This suggests trial populations were fitter and treated more diligently than their real-world comparators. 

The presenter identified the following potential areas where this research could make an impact in clinicians’ daily practice, and some key observations:

  1. The trial cohort are potentially not reflective of real-world, primary care populations – something that is well established
  2. Frail and elderly patients are less likely to receive anticoagulation, leaving them at significantly higher risk of adverse events
  3. As cardiologists we should be available to primary care physicians when a risk vs benefit decision has to made regarding anticoagulation for “higher risk” patients
  4. Whilst there are limitations to this type of study, we are able to identify robust trends and identify at risk patient groups
ESC Congress 2018 - Antithrombosis News


ESC Congress 2018 - Patients with NVAF


ESC Congress 2018 - AF in clinical trials



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