Psychometric evaluation of the Signs of Depression Scale with a revised scoring mechanism in stroke patients with communicative impairment

OBJECTIVES To investigate (1) the diagnostic value of the Signs of Depression Scale (SODS) in a Likert scale format and (2) whether the Likert scale improves the diagnostic value compared with the original dichotomous scale. DESIGN Cross-sectional multicentre study. SETTING One general and one university hospital in the Netherlands. SUBJECTS A total of 116 consecutive hospitalized stroke patients, of whom 53 were patients with communicative impairment. MAIN MEASURES Depression was diagnosed with the Composite International Diagnostic Interview (CIDI) administered to the patients' relatives. The Barthel Index (BI) was used as an external validator. RESULTS The correlation between the CIDI and the SODS-Likert or the SODS was small ( rb = 0.18), and the correlation between the Barthel Index and the SODS-Likert ( rs = -0.30) or the SODS ( rs = -0.33) was moderate. For both instruments, the discriminatory power for diagnosing depression when compared with the CIDI was best at a cut-off score of ⩾2. The internal consistency of the SODS-Likert was acceptable (α = 0.69) and slightly higher than that of the SODS (α = 0.57). The inter-rater reliability of the SODS-Likert and the SODS was acceptable (intraclass correlation coefficient (ICC) 0.66 and ICC 0.80, respectively). The clinical utility was rated good. CONCLUSION The diagnostic value of the SODS did not improve using a Likert scale format. However, the diagnostic value of the original dichotomous SODS is reasonable for the initial mood assessment of stroke patients with communicative impairment.