Responsiveness and construct validity of the Depression, Anxiety, and Positive Outlook Scale (DAPOS)

Background: The Depression, Anxiety, and Positive Outlook Scale (DAPOS) was designed to measure mood in pain populations without contamination from somatic items. Aims: The current study examined responsiveness, internal consistency, and construct validity in pain patients. Method: A questionnaire survey before and after a multi-disciplinary rehabilitation intervention was completed by chronic pain patients, the majority of whom had back pain. Results: The DAPOS showed excellent internal consistency (N = 222, Cronbach alpha = 0.86 for the Depression subscale, 0.90 for the Anxiety subscale, and 0.74 for the Positive Outlook subscale) and construct validity (N = 82) in comparison with a variety of measures (SF-36; Pain Catastrophizing Scale; Zung Depression). Responsiveness was acceptable (ranging between 0.5 and 0.7, for both the mean change in score after treatment to the variability in patients at baseline, and the standardized response mean), although considerably lower than the Zung Depression Inventory. However, reanalysis without somatic items rendered the responsiveness of the Zung inadequate, indicating that change on this measure was due almost entirely to change in somatic symptoms without change in mood. Conclusions: Responsiveness of the DAPOS should be reassessed in treatment targeting mood change explicitly. The DAPOS scales show acceptable clinimetric and psychometric properties, and add a measurement of positive outlook to create a more balanced indication of mood in pain patients.