Development of a candidate item bank for measuring mobility of lower limb orthosis users

Introduction: Orthoses are often prescribed to improve mobility of people with chronic health conditions that affect lower limb function. Patient-reported survey instruments can be used to measure aspects of mobility that cannot be easily assessed in clinical or research settings. A population-specific item bank could be designed to measure aspects of mobility that are most important to lower limb orthosis users and evaluate the effects of orthoses. Objective: The aim of this research was to develop items for a new survey instrument to measure mobility of lower limb orthosis users. Design: A qualitative item review process included focus groups with lower limb orthosis users, an item generation and reduction process that involved a stakeholder advisory panel, and cognitive interviews with target respondents. Setting: Focus groups were held by video conferencing. Cognitive interviews were conducted by telephone. Participants: Focus group and cognitive interview participants were adults with at least six months of experience using a lower limb orthosis that extended from the foot to a level above the ankle. Results: A total of 1,326 extant items were identified in a literature review. Focus group participants (n=29) provided feedback that informed the suitability of a construct definition and conceptual model. An advisory panel contributed to the selection of 118 candidate items for measuring orthotic mobility. Feedback from cognitive interview participants (n = 30) informed removal or revision of problematic items, resulting in a candidate bank of 100 mobility items. Conclusions: The rigorous qualitative methods applied here resulted in a large set of candidate items that spanned a range of situations relevant to moving with a lower limb orthosis. Next steps include administration of the candidate items to a large sample of lower limb orthosis users and calibration of the item bank.