Validation of the Brazilian Version of the World Health Organization Disability Assessment Schedule (WHODAS 2.0) for...

The World Health Organization Disability Assessment Schedule (WHODAS 2.0) is a generic instrument created by the World Health Organization (WHO) for measuring functioning and disability. Although this instrument has been extensively studied in different populations, its validity concerning breast cancer patients who have undergone surgery remains uncharted. This study aims to analyze the measurement properties of the Brazilian version of WHODAS 2.0 to validate it as a tool for assessing the functioning/disability of postoperative breast cancer surgery patients.

This is a validation study conducted at three centers in the northeast of Brazil, involving women between 3 and 12 months after mastectomy or quadrantectomy, interviewed with the Brazilian version of the 36-item WHODAS 2.0. Participants also completed the Functional Assessment of Cancer Therapy (FACT-B+4) questionnaire. Internal consistency was assessed using Cronbach's alpha. Intraclass correlation coefficients (ICC), standard error of measurement (SEM) and smallest detectable change (SDC) were used to measure test-retest reliability. Both construct and convergent validity were analyzed using Spearman correlation.

Ninety-five women with a mean age of 53.12 (± 11.10) answered the WHODAS. The responses revealed satisfactory internal consistency for all domains (α ≥ 0.7) and the total score (α = 0.93). Excellent test-retest reliability was observed (ICC = 0.87). Regarding the construct validity, a strong negative correlation was found between FACT-B+ 4 and WHODAS (ρ = -0.75). Moreover, the convergent validity analysis depicted correlations (between WHODAS and FACT-B+ 4 domains) ranging from weak to moderate, except for the "mobility" subscale of WHODAS, which showed a strong correlation with the "physical well-being" subscale of FACT-B+ 4.

The results provide evidence that the WHODAS 2.0 is a valid and reliable instrument for assessing the functioning/disability of the target population, which allows its use as outcome measure based on the biopsychosocial model.