Generating comprehensive functioning and disability data worldwide: development process, data analyses strategy and reliability of the WHO and World Bank Model Disability Survey

Background Data on functioning and disability collected at population level is essential to complement mortality and morbidity, to estimate rehabilitation needs of countries and regions and to monitor the Convention on the Rights of Persons with Disabilities (CRPD) and the Sustainable Development Goals (SDGs). The objective of this paper is to briefly report the development process of the WHO Model Disability Survey, its data analysis strategy as well as its reliability and ability to measure low to high levels of functioning and disability across countries. Methods The development process is described in detail, and a secondary analysis using Rasch methods is conducted to report reliability and targeting using data from eight national and two regional implementations of the survey. Results The currently available versions of the Model Disability Survey are presented. The survey has good to very good internal reliability and good targeting in all included countries. Conclusion The participatory and evidence-based development, consideration of the expertise of stakeholders, the availability of previously developed ICF-based surveys, and WHO tools targeting functioning and disability are reflected in its good to very good psychometric properties. The survey has been implemented to date in Afghanistan, Cameroon, Chile, Costa Rica, India, Laos, Pakistan, Philippines, Sri Lanka, and Tajikistan, and is used to inform policy-making, to monitor the CRPD and SDGs and to plan the delivery of rehabilitation services.