Assessment of the content validity of the Oswestry Disability Index (ODI) in patients with Degenerative Disc Disease (DDD): a qualitative study

Degenerative disc disease (DDD) is a common disorder that can lead to chronic lower back pain (CLBP). The Oswestry Disability Index (ODI) is a well-established instrument for diseases of the lumbar spine and lower back pain (LBP), covering pain intensity and pain-related disability. This study evaluated the content validity of the modified electronic ODI among patients with DDD and CLBP in the United States (US). Cognitive interviews were conducted with 12 participants from the US diagnosed with DDD and CLBP using a semi-structured interview guide to assess the comprehension and relevance of the ODI. Concept saturation was achieved by the 12th interview. Twelve participants (mean age 40 years old, standard deviation 11 years) including 11 females provided interpretations of the instructions and for each section that were aligned with the intended meanings (11–12/12, ≥ 92%). Sections were relevant to participants’ experience (11–12/12, ≥ 92%), with the sex life section being less relevant (9/12, 75%). Response options were easy to understand. Participants’ interpretations aligned with response options’ intended meanings in 7/10 sections, with less alignment in the lifting, social life, sex life sections due to perceived similarities in ≥ 2 response options. Participants used different recall periods across sections, which was often related to the absence of experiencing the activity at the time of the interview. Most (7/9, 78%) preferred the use of a one-week recall period. This study confirms the content validity of the ODI in patients with DDD. The ODI with a seven-day recall period would be more appropriate for use in this population to evaluate patient outcomes in a clinical trial.