Development and Validation of an Instrument to Determine Patient Knowledge: The Oral Anticoagulation Knowledge Test

Background:Studies examining the relationship between patient knowledge regarding warfarin therapy and its safe and effective use are limited by the lack of validated knowledge assessment tools.Objective:To develop and validate an instrument to assess patient knowledge regarding oral anticoagulation therapy.Methods:Four nationally recognized anticoagulation experts participated in the instrument development process to ensure content validity. The Oral Anticoagulation Knowledge (OAK) test was administered to subjects on warfarin and a group of age-matched subjects not on warfarin to assess construct validity. A subgroup of warfarin subjects were retested approximately 2–3 months after initial testing to assess test–retest reliability. Internal consistency reliability was assessed by calculating a Kuder-Richardson 20 value. Item analysis was used to assess performance of individual questions.Results:An initial 23 item instrument was pilot tested for readability and comprehension. The OAK test was administer...