Background: Content valid, patient-reported outcome (PRO) measures of major depressive disorder (MDD) symptoms are needed to assess MDD treatment benefit. While a range of questionnaires are currently available to evaluate aspects of depression from the patient's perspective, their comprehensiveness and qualitative development histories are unclear.
Objective: The objective of this study was to describe the process and results of the preliminary qualitative development of a new symptom-based PRO measure intended to assess treatment benefit in MDD clinical trials.
Methods: Qualitative interviews were conducted with adult MDD patients in the USA who recently experienced a major depressive episode. Experienced interviewers conducted concept elicitation (CE) and cognitive interviews using semi-structured interview guides. The CE interview guide was used to elicit spontaneous reports of symptom experiences along with probing to further explore and confirm concepts. The cognitive interview guide was developed to evaluate concept relevance, understandability, and structure of the draft items, and to facilitate further instrument refinement.
Results: Forty patients participated in the CE interviews. A total of 3022 symptom codes, representing 84 different concepts were derived from the transcripts. Data from the CE interviews were considered alongside existing literature and clinical expert opinion during an item-generation process, leading to development of a preliminary version of the Symptoms of Major Depressive Disorder Scale (SMDDS). Fifteen patients participated in three waves of cognitive interviews, during which the SMDDS was further refined.
Conclusions: The SMDDS is a 35-item PRO measure intended for use as an endpoint in MDD clinical trials to support medical product labeling. The SMDDS uses a 7-day recall period and verbal rating scales. It was developed in accordance with the US Food and Drug Administration (FDA)'s PRO Guidance and best practices. Qualitative interviews have provided evidence for content validity. Future quantitative studies will confirm the SMDDS's measurement properties and support FDA qualification.