Development and validation of a questionnaire to self-assess patient knowledge of direct oral anticoagulants (KODOA-test).

Objective: Few studies have examined associations between patient knowledge of direct oral anticoagulants (DOAC) and clinical outcomes, mostly because of the lack of validated questionnaires for assessing knowledge. The aim of this study was to develop and validate a questionnaire to self-assess knowledge of DOAC.

Methods: Twelve anticoagulation experts participated in the questionnaire development process to ensure content validity. The Knowledge Of Direct Oral Anticoagulants (KODOA)-test was submitted to patients on DOAC and to pharmacists to assess construct validity. Responsiveness was evaluated after educational counseling. Test-retest reliability was assessed to ensure stability over time, and Cronbach's α was calculated for internal reliability. Index of difficulty and item discrimination (-value) were calculated to assess the performance of single items.

Results: The KODOA-test contains 15 items with multiple-choice answers. Each correct answer scores 1 point (max. score of 15). The KODOA-test was administered to 32 patients on DOAC and 28 pharmacists. Pharmacists scored significantly higher than patients at baseline (median score 13.3 vs 10.0; <0.001), supporting construct validity. Patient scores increased significantly after educational counseling (median score 11 [interquartile range 2] vs 14 [interquartile range 3]; <0.001). Test-retest and Cronbach's α were acceptable with a Pearson's correlation of 0.8 and an α of 0.67. The index of difficulty for most items was satisfactory (0.38-0.72) and the mean -value was 42.5%.

Conclusion: The KODOA-test is a brief, valid, and reliable knowledge self-assessment questionnaire that may be used in clinical trials to investigate associations between knowledge increase and patient-related outcomes.