Self-reported measures in health research for people with intellectual disabilities: an inclusive pilot study on suitability and reliability

Background: The lack of suitable and reliable scales to measure self-reported health and health behaviour among people with intellectual disabilities (ID) is an important methodological challenge in health research. This study, which was undertaken together with co-researchers with ID, explores possibilities for self-reported health scales by adjusting, testing, and reflecting on three self-reported health scales. Methods: In an inclusive process, the researchers and co-researchers with ID adjusted the SBQ (sedentary behaviour), SQUASH (physical activity), and SRH (self-reported health) scales, after which a test-retest study among adults with ID was performed. Test outcomes were analysed on suitability and test-retest reliability, and discussed with the co-researchers with ID to reflect on outcomes and to make further recommendations. Results: Main adjustments made to the scales included: use easy words, short sentences, and easy answer formats. Suitability (N = 40) and test-retest reliability (N = 15) was higher for the adjusted SQUASH (SQUASH-ID), in which less precise time-based judgements are sought, than in the adjusted SBQ (SBQ-ID). Suitability and test-retest reliability were fair to moderate for the SRH-ID and CHS-ID. The main outcome from the reflection was the recommendation to use SQUASH-ID answer options, in which less precise time-based judgements were sought, in the SBQ-ID as well. Conclusions: This study served as a pilot of an inclusive process in which people with ID collaborated in adjusting, testing, and reflecting on self-reported health scales. Although the adjusted self-reported measurements may be reliable and suitable to the target group, the adjustments needed may impair measurement precision. This study's results contribute to informed decision making on the adaptation and use of self-reported health scales for people with ID.