World Health Organisation Disability Assessment Schedule (WHODAS 2.0): development and validation of the Nigerian Igbo version in patients with chronic low back pain.

BACKGROUND Globally, the leading cause of years lived with disability is low back pain (LBP). Chronic low back pain (CLBP) is responsible for most of the cost and disability associated with LBP. This is more devastating in low income countries, particularly in rural Nigeria with one of the greatest global burdens of LBP. No Igbo back pain specific measure captures remunerative or non-remunerative work outcomes. Disability measurement using these tools may not fully explain work-related disability and community participation, a limitation not evident in the World Health Organisation Disability Assessment Schedule (WHODAS 2.0). This study aimed to cross-culturally adapt the WHODAS 2.0 and validate it in rural and urban Nigerian populations with CLBP. METHODS Translation, cultural adaptation, test-retest, and cross-sectional psychometric testing was performed. WHODAS 2.0 was forward and back translated by clinical/non-clinical translators. Expert review committee evaluated the translations. Twelve people with CLBP in a rural Nigerian community piloted/pre-tested the questionnaire. Cronbach's alpha assessing internal consistency; intraclass correlation coefficient and Bland-Altman plots assessing test-retest reliability; and minimal detectable change were investigated in a convenience sample of 50 adults with CLBP in rural and urban Nigeria. Construct validity was examined using Spearman's correlation analyses with the back-performance scale, Igbo Roland Morris Disability Questionnaire and eleven-point box scale; and exploratory factor analysis in a random sample of 200 adults with CLBP in rural Nigeria. Ceiling and floor effects were investigated in both samples. RESULTS Patient instructions were also translated. 'Waist pain/lower back pain' was added to 'illness(es)' to make the measure relevant for this study whilst allowing for future studies involving other conditions. The Igbo phrase for 'family and friends' was used to better represent 'people close to you' in item D4.3. The Igbo-WHODAS had good internal consistency (α = 0.75-0.97); intra class correlation coefficients (ICC = 0.81-0.93); standard error of measurements (5.05-11.10) and minimal detectable change (13.99-30.77). Igbo-WHODAS correlated moderately with performance-based disability, self-reported back pain-specific disability and pain intensity, with a seven-factor structure and no floor and ceiling effects. CONCLUSIONS Igbo-WHODAS appears psychometrically sound. Its research and clinical utility require further testing.