Over the last 3 days we’ve covered The Oral Anticoagulation Knowledge (OAK) Test © Zeolla MM, Brodeur MR, Dominelli A, Haines ST, Allie N. (Q 1-7, Q 8-14, Q 15-20 ). We mentioned that while the pass mark is 15/20 the average mark was 12/20 and 64% of people failed.
If you were among those who failed, take heart at the findings from today’s medical journal article which shows no correlation between OAK tests results and INR control!
The study tested the hypothesis that “patients with higher OAK test scores (i.e. greater knowledge) would have better INR control (primary outcome) and fewer bleeding and thrombosis events (secondary outcomes).”
Where’s the study from?
The study is from British Columbia, Canada of patients attending an anti-coagulation clinic in a tertiary care, university-affiliated hospital, with 20,000 patient-visits per year.
Why was the study done?
The authors state that their hypothesis is controversial and that previous studies of associations between anticoagulant knowledge and clinical outcome had small patient sample sizes and did not use validated questionnaires to assess patients’ knowledge of AC.
What happened in the study?
- 225 patients completed the OAK test.
Mean (SD) age was 70 (13.4) years, 53% were male and 75% were on warfarin for >3 years. Indications for AC were atrial fibrillation in 65%, VTE in 8%, mechanical heart valve in 10%, and other in 19%.
- Their charts were reviewed to obtain information on INR values and any thrombosis or bleeding events during the preceding 1 year period.
- Associations between OAK scores and patient characteristics, INR control and bleeding/thrombosis events were assessed.
What were the results?
- The mean OAK score was 12/20, and 64% failed the OAK test. Predictors of a pass score on the OAK test were younger age (p= 0.01) and higher level of education (p=0.03).
- Over the preceding year, 57.3% of INRs were therapeutic, 25.1% subtherapeutic and 17.4% supratherapeutic, and there were 22 bleeding events and 5 thrombosis events.
- There was no association between OAK score and INR control, or OAK score and bleeding or thrombosis events.
One of the first things I tend to do when reviewing an article is to check which Journal it is from and to see if it is peer reviewed. This article is in a prestigious Journal but is actually the abstract from a poster presented from the American Society of Haematology and is not peer reviewed. Nonetheless it is an interesting premise that there might be a link between people’s knowledge and the level of anticoagulant control.
My initial thought was that it is reasonable especially as we emphasise the importance of people’s involvement in their care, but in reality the variation in drug metabolism between individuals is probably the major reason for the wide variability in anticoagulant control.
This doesn’t mean you shouldn’t learn about warfarin as it is very important to be aware of the risks of bleeding and drug interactions. It’s also hard to believe that a study of a relatively small number of people with only a few events will show a significant difference.
What’s the study reference?
Patients’ Knowledge Of Anticoagulation and Its Association With Clinical Characteristics, INR Control and Warfarin-Related Adverse Events, Poupak Rahmani, Charlotte L. Guzman, Mark D Blostein, Ashley Tabah, Alla Muladzanov and Susan R. Kahn