Comparison of the 12-item and 36-item versions of the World Health Organization Disability Assessment Schedule (WHODAS) 2.0 using longitudinal data from community mental health outreach service users.

Aim: This study aimed to compare the 12-item and 36-item versions of the World Health Organization Disability Assessment Schedule (WHODAS) 2.0 using longitudinal data from community mental health outreach service users.

Methods: Using data from Tokorozawa City mental health outreach service users in Japan, total and domain WHODAS-12 and WHODAS-36 scores were compared. First, we examined score-change differences by domain at the start of outreach services (T1) and 1 year later (T2) for each version. Next, we compared differences between the two versions using Pearson's correlation, Wilcoxon signed-rank test, and Bland-Altman analysis.

Results: Among 20 participants, total scores and scores of some domains (i.e., cognition, getting along, life activities, and participation) were significantly lower at T2 than at T1 on both versions (p < 0.010). WHODAS-36 scores were significantly lower at T2 than at T1 for the self-care domain (p = 0.018). Except for self-care, strong correlations were found between scores from the two versions (p < 0.001). In the Wilcoxon signed-rank test and Bland-Altman analysis, we found significant differences between the scores of the two versions in the mobility, self-care, and participation domains. There were no significant differences in the distribution or systematic errors between the two versions in scores for the other domains or total score.

Conclusion: We found strong positive correlations between WHODAS-12 and WHODAS-36 total scores with no statistical differences between them. For some domains, differences in distribution and systematic errors were found.