Development and validation of a new instrument for testing functional health literacy in Japanese adults.

This study aimed to develop a reliable and valid measure of functional health literacy in a Japanese clinical setting. Test development consisted of three phases: generation of an item pool, consultation with experts to assess content validity, and comparison with external criteria (the Japanese Health Knowledge Test) to assess criterion validity. A trial version of the test was administered to 535 Japanese outpatients. Internal consistency reliability, calculated by Cronbach's alpha, was 0.81, and concurrent validity was moderate. Receiver Operating Characteristics and Item Response Theory were used to classify patients as having adequate, marginal, or inadequate functional health literacy. Both inadequate and marginal functional health literacy were associated with older age, lower income, lower educational attainment, and poor health knowledge. The time required to complete the test was 10-15 min. This test should enable health workers to better identify patients with inadequate health literacy.