Validity and reliability of the Chinese version of the Sheehan Disability Scale (SDS-C)

Introductions: This study aims to evaluate the validity and reliability of the Chinese version of the Sheehan Disability Scale (SDS-C) among depression patients in Taiwan. Methods: To validate the SDS-C, two samples were selected: Sample 1 (n=78) consisted of patients diagnosed with Depressive Disorder, while sample 2 (n=63) consisted of a nondepressive population. Sample 1 was evaluated with SDS twice with 7-14 days interval to measure test-retest reliability. Both samples were also evaluated with The Centre for Epidemiologic Studies Depression Scale (CESD), Family APGAR (adaptation, partnership, growth, affection, resolve) score, the Global Assessment of Functioning (GAF), and brief questionnaire of the World Health Organization Quality of Life instrument (WHOQOL-BREF) and by a psychiatrist. The two samples were combined to measure validity. Results: In concurrent validity, SDS-C scores were significantly correlated with the total score of GAF. The discriminative validity was carried out by comparing the score of SDS-C between subjects with and without current depressive disorder (t=12.32, df=139, P<0.001). Another discriminative validity by receiver-operating characteristic analysis showed the optimal cut-point was >11 (sensitivity: 82.1, specificity: 93.7). The area under the curve was 0.93 (±0.02). For the factor validity, principal components analysis showed that a single factor solution was the best solution accounting for 88.9% of the variance. Regarding the construct validity, SDS-C scores were significantly correlated with CESD, WHOQOL-BREF, and the Family APGAR score. For test-retest reliability, the intra-class correlation coefficient for the total SDS-C score was 0.89 (95% confidence interval 0.82-0.93) and internal consistency Cronbach's alpha was 0.94. Discussion: The SDS-C was found to be a valid and reliable instrument for current depressive disorder patients in Taiwan.