A psychometric analysis of the Clinically Useful Depression Outcome Scale (CUDOS) in Spanish patients.

Background: Psychometrically sound and time-efficient scales that measure depressive symptoms are essential for research and clinical practice. This study was aimed at exploring the psychometric properties of the Spanish version of the Clinically Useful Depression Outcome Scale (CUDOS) in a clinical sample.

Method: Participants were 162 patients (72% women) with a mood disorder (86% diagnosed as major depressive disorder). Depressive symptoms were assessed by means of the CUDOS, the Beck Depression Inventory (BDI), and two interviewer-rated instruments: the 17-item Hamilton Depression Rating Scale (HDRS17) and the Clinical Global Impression-Severity (CGI-S) scale. Dimensionality, internal consistency, test-retest reliability, construct validity, criterion validity, and responsiveness to change of the CUDOS were explored.

Results: The CUDOS exhibited a one-factor structure which accounted for 55.7% of the variance, and excellent results for internal consistency (Cronbach's alpha=0.93), for test-retest reliability (intraclass correlation coefficient=0.84) and for convergent validity [HDRS17 (r=0.77), CGI-S (r=0.73) and BDI (r=0.89)]. The ability of the CUDOS to identify patients in remission was high (area under ROC curve=0.96). Its responsiveness to change was also highly satisfactory: patients with greater clinical improvement showed a greater decrease in CUDOS scores (p<0.001).

Limitations: Diagnoses, even though made by expert clinicians, were established as part of routine clinical practice. Generalizability of the findings beyond the study sample is unknown.

Conclusions: The findings suggest that the Spanish version of the CUDOS is valuable as a brief and psychometrically sound self-report instrument to assess depressive symptoms in research and in clinical practice.