Psychometric evaluation of the WHODAS 2.0 and prevalence of disability in a Swedish general population.

BACKGROUND: The World Health Organization Disability Assessment Schedule (WHODAS 2.0) is a generic questionnaire that captures health and disability-related functioning information corresponding to six major life domains: Cognition, Mobility, Self-care, Getting along, Life activities, and Participation. The WHODAS 2.0 is used in a wide range of international clinical and research settings. A psychometric evaluation of WHODAS 2.0, Swedish version, in the general population is lacking, together with national reference data to enable interpretation and comparison. This study aims to evaluate the psychometric properties of the Swedish 36-item version of WHODAS 2.0 and describe the prevalence of disability in a Swedish general population. METHODS: A cross-sectional survey was performed. Internal consistency reliability was assessed with Cronbach's alpha. The construct validity was evaluated with item-total correlation, Pearson's correlation between the WHODAS 2.0 domains and the RAND-36 subscales, analysis of known groups by one-way ANOVA, and analysis of the factor structure by confirmatory factor analysis. RESULTS: Three thousand four hundred and eighty two adults aged 19-103 years (response rate 43%) participated. Significantly higher degrees of disability were reported by the oldest age group (≥ 80 years), adults with a low level of education, and those on sick leave. Cronbach's alpha was from 0.84 to 0.95 for the domain scores and 0.97 for the total score. The item-scale convergent validity was satisfactory, and the item-scale discriminant validity was acceptable except for the item about sexual activity. The data partially supported the factor structure, with borderline fit indices. CONCLUSION: The psychometric properties of the self-administered Swedish 36-item version of the WHODAS 2.0 are comparable to those of other language versions of the instrument. Data of the prevalence of disability in Swedish general population enables normative comparisons of WHODAS 2.0 scores of individuals and groups within clinical practice. The instrument has certain limitations that could be improved on in a future revision. The test-retest reliability and responsiveness of the Swedish version of WHODAS 2.0 for different somatic patient populations remain to be evaluated.

The Swedish RAND-36: psychometric characteristics and reference data from the Mid-Swed Health Survey.

BACKGROUND: This study aims to evaluate data quality, scaling properties, and reliability of the Swedish RAND-36 in a general population sample and to present reference data for the Swedish population. METHODS: Testing of data quality, scaling assumptions and reliability followed methods recommended for the International Quality of Life Assessment Project, previously used for psychometric testing of SF-36 and RAND-36. Data were collected via regular mail for a random stratified sample of the general population in a Swedish county. Weighted means for RAND-36 scores were used and differences by sex, age, education, and occupational groups were tested. RESULTS: The response rate was 42%, and the sample comprised 3432 persons (45% men, 55% women) with a median age of 56.9 years. The internal consistency reliability was satisfactory, with Cronbach's alphas > 0.80 for all eight scales. The percentage of missing items was low, ranging between 1.3% and 3.2%. No floor effects (≥15%) were noted, while ceiling effects were observed for physical functioning, role-functioning/physical, pain, role-functioning/emotional, and social functioning. Item-scale correlations were satisfactory (r ≥ 0.40). Correlations among the physical health scales were strong (range 0.58-0.68) as were the correlations among the mental health scales (range 0.58-0.73). Men reported significantly better health-related quality of life (HRQoL) on all scales, although the gender differences were small. Comparisons among age groups showed approximately equal scores among those 20-29, 30-39, and 40-49 years, while significant decreases in physical health were observed in the older age groups. Substantially worse physical health scores were observed in the oldest age group (80+). Significant differences among age groups were noted also for the mental health scales; however, better energy/fatigue and emotional well-being scores were seen in the older age groups, except for the oldest (80+). Those with university education reported significantly better scores on all scales compared to those with mandatory education. CONCLUSIONS: The study suggests that the Swedish version of RAND-36 is an acceptable and reliable instrument for measuring HRQoL in the general population. The study provides reference data that can be used for norm-based comparisons.