WHO Disability Assessment Schedule 2.0 (WHODAS 2.0)

WHODAS 2.0 supersedes WHODAS II and is an altogether different instrument that is grounded in the conceptual framework of the ICF. It integrates an individual's level of functioning in major life domains and directly corresponds with ICF's "activity and participation" dimensions.

WHODAS 2.0 was developed through a collaborative international approach with the aim of developing a single generic instrument for assessing health status and disability across different cultures and settings.

The collaborative international research involved in developing WHODAS 2.0 included:

• Critical review of conceptualization and measurement of functioning and disability as well as a review of existing instruments
• Cross-cultural application study spanning 19 countries around the world
• Reliability and validity field studies including two waves of international testing using a multicentre design with identical protocols

Versions

Depending on the information needed, the study design and the time constraints, the user may choose between multiple versions with different options for administration:

36-item version
Provides most detail
Allows to compute overall and 6 domain-specific functioning scores
Available as interviewer-, self-, and proxy-administered forms
Average interview time: 20 min.

12-item version
Useful for brief assessments of overall functioning in surveys
Allows to compute overall functioning scores
Explains 81% of the variance of the 36-item version
Available as interviewer-, self-, and proxy-administered forms
Average interview time: 5 min.

Administration

Self-administration: A paper-and-pencil version of WHODAS 2.0 can be self-administered.
Interview: WHODAS 2.0 can be administered in person or over the telephone. General interview techniques are sufficient to administer the interview in this mode.
Proxy: Sometimes it may be desirable to obtain a third-party view of functioning such as; family members, caretakers or other observers.

Scoring

There are two basic options for computing the summary scores for the WHODAS 2.0 short and full versions
Simple: the scores assigned to each of the items – “none” (0), “mild” (1) “moderate” (2), “severe” (3) and “extreme” (4) – are summed. This method is referred to as simple scoring because the scores from each of the items are simply added up without recoding or collapsing of response categories; thus, there is no weighting of individual items. This approach is practical to use as a hand-scoring approach, and maybe the method of choice in busy clinical settings or in paper-pencil interview situations. As a result, the simple sum of the scores of the items across all domains constitutes a statistic that is sufficient to describe the degree of functional limitations.
Complex: The more complex method of scoring is called “item-response-theory” (IRT) based scoring. It takes into account multiple levels of difficulty for each WHODAS 2.0 item. It takes the coding for each item response as “none”, “mild”, “moderate”, “severe” and “extreme” separately, and then uses an algorithm to determine the summary score by differentially weighting the items and the levels of severity. The SPSS algorithm is available from WHO. The scoring has three steps:

• Step 1 – Summing of recoded item scores within each domain.
• Step 2 – Summing of all six domain scores.
• Step 3 – Converting the summary score into a metric ranging from 0 to 100 (where 0 = no disability; 100 = full disability).

To download scoring templates please click the following links:

Please note that the question responses for WHODAS 2.0 have not changed (No Difficulty, Mild Difficulty, Moderate Difficulty, Severe Difficulty, and Extreme Difficulty or Cannot Do), but the numbers assigned to them have (using a 5 point scale from 0-4 rather than from 1-5). This is in response to feedback received, and will not change the final score provided that you use the correct scale for the correct method. Use the 0-4 scale for these templates, only.

• 12-item Instrument Scoring Sheet
• 36-item Instrument Scoring Sheet, Simple Scoring Calculation
• 36-item Instrument Scoring Sheet, Domain-Weighted Scoring Calculation

WHODAS 2.0 Domain Scores

WHODAS 2.0 produces domain-specific scores for six different functioning domains – cognition, mobility, self-care, getting along, life activities (household and work) and participation.

Psychometric Qualities

• Test-retest studies of the 36-item scale in countries across the world found it to be highly reliable.
• All items were selected on the basis of item–response theory (i.e. the application of mathematical models to data gathered from questionnaires and tests).
• Showed a robust factor structure (see below) that remained constant across cultures and different types of patient populations.
• The validation studies also showed that it compared well with other measures of disability or health status, and with clinician and proxy ratings.

In all cultures and populations tested, factor analysis revealed a robust factor structure on 2 levels

• First level: General disability factor
• Second level: Different life domains based on ICF

WHODAS 2.0 Population Norms

Please click here for the population norms for IRT-based scoring of the WHODAS 2.0 and the population distribution of IRT-based scores for WHODAS 2.0

Development History

• To emphasize the need for standardized cross-cultural measurement of health status, WHO developed a general measure of functioning and disability in major life domains.
• The original Disability Schedule WHO/DAS published by WHO in 1988 – was an instrument developed to assess functioning, mainly in psychiatric inpatients.
• WHODAS 2.0 superseded WHODAS II and is an altogether different instrument that is grounded in the conceptual framework of the ICF.
• It integrates an individual's level of functioning in major life domains directly corresponds with ICF's "activity and participation" dimensions.

Process of development

WHODAS 2.0 was developed through a collaborative international approach, with the aim of developing a single generic instrument for assessing health status and disability across different cultures and settings.
The collaborative international research involved in developing WHODAS 2.0 included:

• A critical review of conceptualization and measurement of functioning and disability, and existing instruments.
• Cross-cultural application study spanning 19 countries around the world. The items were selected after exploring how health status is assessed in different cultures through a process that involved linguistic analysis of health-related terms, interviews with key informants and focus group discussions, as well as qualitative methods (e.g. pile sorting and concept mapping).
• Reliability and validity field studies including two waves of international testing using a multicentre design with identical protocols. These studies included cognitive interviews to determine how well the respondents understood the questions and reacted to the contents of the WHODAS 2.0. They also involved checking the reliability of a shortened, 36-item version of the WHODAS 2.0 by means of a standard statistical procedure, in line with classic test and item response theory (IRT).