Similar to researches conducted by Shrestha5 et al, Hu13 et al and Baker11 et al, our study showed that patients have low knowledge with regards to their prescribed OAC. Taking the demographics into account, one can reasonably attribute the lack of higher education and a language barrier as the primary causes of this gap in knowledge. However, previous literature regarding the association of knowledge with age has mixed findings. Some researchers conclude that participants of younger age and higher level of education scored better, 14,15 whereas others showed older age to positively influence the scores.16 Our study does not show any significant relation of knowledge with participants’ age.
Findings of our study indicate that only 27.1% of the participants correctly identified bleeding as the most important side effect of this medication, particularly bleeding from gums, prolonged nosebleeds and blood in urine. The majority of the sample (65.7%) did not know what side effects to be wary of or how to reduce their risk. These findings prove to be an alarming indicator of lack of awareness as most of these participants had been asked to continue this medicine for life and their lack of knowledge about possible side effects is concerning. This gap in knowledge is common in reference to many studies, one of which reported only 42% of their sample population to be aware of any possible side effects of warfarin therapy. 17
Another particular area of concern was the inadequate patient understanding of warfarin’s interactions. Majority of the participants were unaware of the interaction of OAC drugs with over the counter pills like aspirin, herbal medicines and alcohol. Drugs such as Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) and aspirin inhibit platelet function therefore when coupled with oral anticoagulants, they may increase the risk of bleeding. 18 There is a high prevalence of multiple NSAIDs prescription in Pakistan19, an alarming fact when considering that NSAIDs increase the risk of gastrointestinal bleeding when used in combination with warfarin, and that only a minority of our sample was aware of this interaction. Alcohol, on the other hand, interacts with the cytochrome P450 system, responsible for metabolizing warfarin. Only one third of the study population understood the risk of concurrent use of alcohol and an even smaller percentage to that with NSAIDs. A similar finding was obtained by Shrestha et al5, who reported that 94.1% of their sample did not know which drinks could decrease warfarin’s effectiveness. This is particularly worrying when taking into consideration the fact that excess alcohol can increase the risk of major bleeding when taken with warfarin, and only 23.7% of our sample could identify bleeding as the most important side effect of oral anticoagulants. These findings were similar to results obtained by Roche6 et al, Yahaya20 et al and Campbell et al21.
The sample population barely knew about INR, its target values and the importance of therapeutic INR range; attaining a mean score of only 14.6(± 16.4)%. Furthermore, a research also found that even though young and educated people are likely to have better knowledge about their anticoagulant medicines, this does not affect their INR control or episodes of bleeding and/or thrombosis.23 On the contrary, a research in Saudi Arabia showed INR control to be positively influenced by knowledge about their OAC.24 Maintaining a stable INR is an important indicator of adequate anticoagulation in the body, because supratherapeutic value increases the probability of bleeds and subtherapeutic value may cause thrombosis.25 Within our sample population, the ability to self-monitor is likely to be reduced due to their lack of adequate knowledge about INR, increasing the probability of patients being under or over treated.
A positive result identified in our patient population indicated that over three quarters of people agreed it was important for their healthcare providers to know they were taking an OAC, and the similar proportion of people said that they would usually inform their doctors about their drug history. In contrast, Khudair et al26 found that most participants did not know the importance of informing healthcare professionals if they were on warfarin.