Development of Disability Measures for Surveys: The Washington Group Extended Set on Functioning

Abstract

Introduction: Measuring disability Disability represents a complex process and is not a single, static state. It refers to the outcome of the interaction of a person and his/her environment (physical, social, cultural or legislative) and represents a measure of the negative impact of environmental factors on one's ability to participate. The complexity of the concept has resulted in the proliferation of statistics on disability that are neither comparable nor easy to interpret. Furthermore, disability data are collected for different purposes, such as to estimate the prevalence of physical impairments or to plan for the provision of services. Each purpose elicits a different statistic and even when the intention is to measure the same concept, the actual questions used differ in ways that severely limit comparability. Furthermore, different data collection formats require different means to collect data. For example, censuses are necessarily short, and restrictions are placed on space that in turn limits the number of questions asked to capture the construct of interest. Surveys, on the other hand, may focus broadly on aspects of health, education and/or labor practices-or may focus more specifically on, for example, disability. For surveys more time is allotted to data collection, more questions are asked and more detailed information is collected. Each format requires its own set of questions. The development of a short set of disability questions suitable for censuses has been completed and is documented in greater detail elsewhere (see: https://www.washingtongroup-disability.com/fileadmin/uploads/wg/Documents/Questions/new_WG_Implementation_Docume nt__2_-_The_Washington_Group_Short_Set_on_Functioning__1_.pdf). This document will introduce the work of the Washington Group on Disability Statistics (WG), the Budapest Initiative (BI) and the United Nations Economic & Social Commission for Asia & the Pacific (UNESCAP) and chart the development of an extended set of disability questions for surveys that focus on functioning (WG-ES). The Washington Group on Disability Statistics (WG) chose to develop questions that would address the issue of whether persons with disability participate to the same extent as persons without disabilities in activities such as education, employment or family/civic life. WG questions are designed to provide comparable data cross-nationally for populations living in a variety of cultures with varying economic resources. The WG short set of questions were developed primarily for use in National Censuses or surveys focuses on topics other than disability such as labor force or living standards surveys where space for questions is limited. The WG short set of questions, structured within the framework of the International 2 Classification of Functioning, Disability and Health (ICF), has been shown to produce internationally comparable data [1]. It is intended that these questions will identify the majority of persons in the population who are at greater risk than the general population of experiencing limited or restricted participation in society. The questions cover six domains of functioning: seeing, hearing, walking, cognition, self care, and communication. In 2008, the United Nations Statistical Division (UNSD) presented Principles and Recommendations for Population and Housing Censuses (2nd Revision)-a document that endorses the approach taken by the WG regarding the measurement of disability. (See: Section VI-8: Disability Characteristics pages 178-183; available online at: http://unstats.un.org/unsd/demographic/sources/census/docs/P&R_Rev2.pdf). The WG then turned to the development of extended sets of questions for surveys. The Budapest Initiative (BI), established 2005, is a collaboration of, among others, the World Health Organization (WHO), United Nations Economic Commission for Europe (UNECE), and Eurostat. This consortium was charged with the task of developing a short form questionnaire intended to provide the basis for the collection of comparable standardized information on population health focusing on health state for inclusion in the European Health Interview Survey (EHIS). The BI defines health state in terms of functioning in a core set of health domains; and, like the WG, the BI has based the development of its questionnaire on a conceptual framework: the ICF. The first set of questions developed by the BI-referred to as the Budapest Initiative-Mark 1 (BI-M1)-addressed functional domains that met a specific set of criteria. These related to relevance and feasibility as well as certain measurement characteristics. The domains and questions had to be plausible and reasonable, to span the main aspects of health experienced by the population, and to be seen as significant aspects of individuals' health. Furthermore, the parsimonious question set had to be suitable for use in health interview surveys, maintain a consistent meaning in different social contexts, and be able to demonstrate a reasonable degree of heterogeneity within the population being surveyed. BI-M1was completed in 2007 but it was recognized that additional work was needed so that additional key domains could be included. Background & the Development of Extended Set Questions: In 2008, the work being conducted by the WG, the BI and UNESCAP was brought together under a common umbrella.