Patient knowledge of anticoagulant treatment does not correlate with treatment quality

The objectives of this study were to investigate whether patient knowledge is a predictor of treatment stability in anticoagulant clinic patients and to evaluate the correlation between the patients' subjective assessment of own knowledge and their score on a validated knowledge assessment instrument.

This is a prospective study where international normalized ratio (INR) stability was followed up 6 months after knowledge assessment.

We analyzed data of 42 consecutive patients new to vitamin-K antagonist (VKA) treatment and 64 experienced patients from an anticoagulant clinic offering patient education. The patients filled out a VKA knowledge assessment questionnaire with 24 items under standardized conditions, and simultaneously, they were asked about their subjective knowledge. Subsequently, time in range of INR (TIR) was collected for each patient.

Out of the 106 patients, 52 had 18 or more correct answers (>75%), defined as a 'satisfactory level' of objective knowledge. The average TIR was 73%, and treatment stability was significantly higher in experienced patients than new patients. We found no correlation between objective knowledge and TIR (Spearman rho = -0.03, P = 0.78). Most patients (77%) reported a high subjective knowledge of VKA, but no correlation was found between objective and subjective knowledge (Spearman rho = 0.129, P = 0.19).

We observed that many patients had a low level of knowledge of VKA, despite high treatment stability and patient education. The patient's own assessment of knowledge was not found to predict objective knowledge, which could have implications for selection of patients for self-test or self-management of treatment.