Development and content validation of a financial and functional outcomes tool for diabetes-related foot disease in patients undergoing major lower limb amputation: a prospective observational study from Pakistan

Objective To develop and content validate a questionnaire to assess the financial and functional impact of major lower limb amputation in patients with diabetes-related foot disease. Design Prospective observational study. Setting This study was conducted at a tertiary care centre in Pakistan. Participants We conducted a thorough literature review and a group interview with 10 participants, resulting in domain identification and item generation. The group included seven patients with diabetes-related foot disease who underwent major lower limb amputation and three caregivers. Subsequently, a focused group discussion was held to assess overlap and duplication among the items, and two rounds of content validation were carried out by five content and five lay experts in both English and Urdu. Question items with a Content Validity Index (CVI) score of >0.79 were retained, items with a CVI score between 0.70 and 0.79 were revised and items with a CVI score of <0.70 were excluded. Results The initial literature review and group interview resulted in 61 items in the financial and functional domains. After the focused group discussion, the questionnaire was reduced to 37 items. Following two rounds of content validation, the English questionnaire achieved the Scale-Content Validity Index/Average (S-CVI/Ave) of 0.92 and 0.89 on relevance and clarity, respectively. Similarly, the Urdu questionnaire achieved the S-CVI-Ave of 0.92 and 0.95, respectively. Conclusion A 37-item multidimensional questionnaire was developed and rigorously content-validated to assess the financial and functional impact of major lower limb amputation in patients with diabetes-related foot disease. The questionnaire used in this study has shown robust content validity specifically for our population.