Development and Validation of the 34-Item Disability Screening Questionnaire (DSQ-34) for Use in Low and Middle Income Countries Epidemiological and Development Surveys.

BACKGROUND Although 80% of persons with disabilities live in low and middle-income countries, there is still a lack of comprehensive, cross-culturally validated tools to identify persons facing activity limitations and functioning difficulties in these settings. In absence of such a tool, disability estimates vary considerably according to the methodology used, and policies are based on unreliable estimates. METHODS AND FINDINGS The Disability Screening Questionnaire composed of 27 items (DSQ-27) was initially designed by a group of international experts in survey development and disability in Afghanistan for a national survey. Items were selected based on major domains of activity limitations and functioning difficulties linked to an impairment as defined by the International Classification of Functioning, Disability and Health. Face, content and construct validity, as well as sensitivity and specificity were examined. Based on the results obtained, the tool was subsequently refined and expanded to 34 items, tested and validated in Darfur, Sudan. Internal consistency for the total DSQ-34 using a raw and standardized Cronbach's Alpha and within each domain using a standardized Cronbach's Alpha was examined in the Asian context (India and Nepal). Exploratory factor analysis (EFA) using principal axis factoring (PAF) evaluated the lowest number of factors to account for the common variance among the questions in the screen. Test-retest reliability was determined by calculating intraclass correlation (ICC) and inter-rater reliability by calculating the kappa statistic; results were checked using Bland-Altman plots. The DSQ-34 was further tested for standard error of measurement (SEM) and for the minimum detectable change (MDC). Good internal consistency was indicated by Cronbach's Alpha of 0.83/0.82 for India and 0.76/0.78 for Nepal. We confirmed our assumption for EFA using the Kaiser-Meyer-Olkin measure of sampling well above the accepted cutoff of 0.40 for India (0.82) and Nepal (0.82). The criteria for Bartlett's test of sphericity were also met for both India (< .001) and Nepal (< .001). Estimates of reliability from the two countries reached acceptable levels of ICC of 0.75 (p<0.001) for India of 0.77 for Nepal (p<0.001) and good strength of agreement for weighted kappa (respectively 0.77 and 0.79). The SEM/MDC was 0.80/2.22 for India and 0.96/2.66 for Nepal indicating a smaller amount of measurement error in the screen. CONCLUSIONS In Nepal and India, the DSQ-34 shows strong psychometric properties that indicate that it effectively discriminates between persons with and without disabilities. This instrument can be used in association with other instruments for the purpose of comparing health outcomes of persons with and without disabilities in LMICs.