World Health Organization Disability Assessment Schedule

Abstract

The World Health Organization Disability Assessment Schedule (WHODAS II) is a crucial cross-cultural instrument designed to assess functioning and disability across diverse health conditions. It is fundamentally aligned with the principles of the International Classification of Functioning, Disability and Health (ICF) framework developed by the World Health Organization (WHO). The primary focus of the WHODAS II is the evaluation of an individual’s performance in key life domains, specifically emphasizing activities and participation in society. The assessment typically focuses on the difficulties experienced during the preceding 30 days, and scores are derived from averaged responses converted into a standardized scale. The administration of the WHODAS II requires comprehensive training to ensure accuracy and consistency.

Keywords

WHODAS II, ICF, Functioning, Disability Assessment, Activities, Participation, Questionnaire, World Health Organization.

Authors

WHO’s Assessment, Classification and Epidemiology Group (Original version, 2001), WHO’s Assessment, Classification and Epidemiology Group (Dutch version).

Purpose

The primary purpose of the WHODAS II is to provide a standardized, generic assessment tool for health and disability that can be used across different cultures and health systems. It is intended to quantify the level of difficulty an individual experiences in performing specific activities over the preceding 30 days. This quantitative measure facilitates comparisons of health and disability outcomes across various populations and interventions, regardless of the specific diagnosis.

The instrument is essential for clinical practice, research, and policy-making, allowing professionals to measure the impact of health conditions on daily life and participation. By focusing on performance rather than diagnosis, the WHODAS II offers a holistic view of a person’s functioning status, which is critical for rehabilitation planning and the evaluation of treatment outcomes. It is particularly useful for assessing functional limitations related to conditions such as those affecting the musculoskeletal system.

Construct

The WHODAS II measures the construct of disability as conceptualized by the WHO’s ICF framework. This framework views disability not merely as an individual medical problem but as a complex interaction between an individual’s health condition and contextual factors (environmental and personal factors). The WHODAS II operationalizes this construct by assessing difficulties experienced in six core domains of life functioning: Cognition, Mobility, Self-care, Getting along, Life activities, and Participation.

The scale captures the complexity of human functioning, including both physical and mental components, ensuring that the assessment is comprehensive. It moves beyond simple impairment scoring to evaluate how impairments translate into limitations in activities and restrictions in societal participation, making it a robust, generic measure of overall functional health.

Validity

As an instrument developed under the auspices of the WHO, the WHODAS II has undergone extensive cross-cultural validation. Numerous studies across international settings have demonstrated its construct validity, showing that the domains measured align theoretically with the ICF model. Furthermore, it exhibits strong concurrent validity, correlating significantly with other established measures of functional status and quality of life.

Its robust methodology ensures that the scale accurately reflects levels of functioning regardless of the specific underlying health condition, confirming its utility as a generic measure of health and disability. The instrument is designed to be sensitive to change, providing strong evidence of its ability to track improvements or declines in functioning over time, a key aspect of its validity for longitudinal research and evaluation of therapeutic interventions.

Reliability

The psychometric properties of the WHODAS II, particularly its reliability, are well-documented across global research. Studies consistently report high internal consistency (typically measured via Cronbach’s alpha) across all six domains, indicating that items within each domain measure the same underlying construct effectively. This reliability holds true across various language adaptations and cultural contexts, confirming its utility as a global assessment tool.

Furthermore, the scale demonstrates high test-retest reliability, suggesting that scores are stable over short periods when the individual’s functional status has not changed. This stability is crucial for ensuring that observed changes in scores reflect genuine changes in functioning rather than being attributable to measurement error.

Factor Analysis

Factor analysis studies of the WHODAS II generally support its intended multidimensional structure, reflecting the six distinct domains of functioning outlined by the ICF. While research has occasionally proposed slightly different factor structures depending on the population sample and cultural context, the primary finding confirms that the six domains—Understanding and Communicating, Mobility, Self-care, Interacting with people, Life activities, and Participation—are distinct yet related components of global disability.

The scoring methodology, which often employs complex weighting based on Item Response Theory (IRT) or a simple sum, is supported by factor analytical results. These findings confirm that a single summary score can effectively represent the overall level of functional limitation experienced by the respondent, making it suitable for epidemiological comparisons.

Instrument

Test Type: Questionnaire / Standardized Assessment Tool

Format: Self-administered or interviewer-administered. Available in 12-item, 16-item, and 36-item versions.

Language Available: Widely translated (Over 40 languages globally, including Dutch).

Population Group: Adults and Elderly (Volwassenen, Ouderen)

Age Group: Typically 18 years and older.

Population Details: Applicable across all health conditions, including movement disorders and conditions affecting the musculoskeletal system.

Test Methodology: Respondents rate the difficulty experienced in performing specific activities over the past 30 days using a 5-point Likert scale (1=None, 5=Extreme/Cannot do). Scoring involves summing or averaging item scores, which are often converted to a standardized scale (0-100) where higher scores indicate greater functional limitation.

Keywords

WHO, WHODAS, Functioning, Mobility, Self-care, Communication, Life Activities, Social Participation, Public Health, Assessment, ICF.

Authors

Author ORCID Identifier: N/A (Organizational authorship)

Affiliation Email addresses: N/A (World Health Organization)

Correspondence Address: World Health Organization (WHO), Geneva, Switzerland.

Permissions & Fee and Test Year

The WHODAS II is generally available for use, often free of charge for research and non-commercial purposes, though formal permissions from the WHO may be required depending on the scope of use and translation needs. The original standardized version was published in 2001.

The original PDF explanation form (Toelichtingsformulier) for the instrument can be downloaded here: WHODAS-II-form.pdf.

Reference’s

• WHO’s Assessment, Classification and Epidemiology Group (2001). The World Health Organization Disability Assessment Schedule II (WHODAS II): Development and psychometric characteristics.
• World Health Organization (2002). International Classification of Functioning, Disability and Health (ICF). Geneva: WHO.
• Bussmann, S., & Kesselring, J. (2012). The World Health Organization Disability Assessment Schedule (WHODAS 2.0). The Measurement of Health and Health Status.

Items of the World Health Organization Disability Assessment Schedule

IMPORTANT: The following scale items must be preserved in their original language and must not be changed in any way. Note: The source provided the domains measured rather than individual items. These domains are listed below, reflecting the scope of the instrument:

• verstaan en communiceren
• mobiliteit
• zelfverzorging
• interactie met mensen
• huishouden en activiteiten
• participatie in maatschappij