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Value Health. 2019 Aug;22(8):906-915. doi: 10.1016/j.jval.2019.02.010. Epub 2019 May 17.

Symptoms of Major Depressive Disorder Scale: Performance of a Novel Patient-Reported Symptom Measure.

Author information

1
Evidera, Seattle, WA, USA. Electronic address: don.bushnell@evidera.com.
2
Patient-Reported Outcomes and Clinical Outcomes Assessment Center of Excellence, Pharmerit International, Seattle, WA, USA.
3
Global Patient-Focused Outcomes Center, Eli Lilly and Company, Indianapolis, IN, USA.
4
Pfizer Ltd, Tadworth, Surrey, UK.
5
Global Commercial Strategy Organization, Janssen Global Services, LLC, Fremont, CA, USA.
6
PCOR Neurosciences, Roche UK, Welwyn Garden City, UK.
7
Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX, USA.
8
Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
9
Brown University, Providence, RI, USA.
10
Critical Path Institute, Patient-Reported Outcome Consortium, Tucson, AZ, USA.

Abstract

BACKGROUND:

The Symptoms of Major Depressive Disorder Scale (SMDDS) was expressly developed on the basis of qualitative data to directly incorporate patients' voices into evaluation of treatment benefit in major depressive disorder (MDD) clinical trials.

OBJECTIVES:

To collect quantitative data necessary to refine/optimize the SMDDS and document its psychometric properties.

METHODS:

In this multicenter, observational study, participants with clinically diagnosed MDD completed questionnaires in 2 waves. Wave 1 was designed to refine the SMDDS using Rasch measurement evaluations and item reduction analyses. On a subset of wave 1 subjects, 7 to 12 months later, wave 2 further examined item performance and measurement properties. Exploratory factor analyses and assessments of construct validity and reliability (internal consistency and reproducibility) were completed.

RESULTS:

Using wave 1 data (N = 315; females = 71%, white = 81%, mean age = 44 years), the SMDDS was revised from 36 to 16 items. The Rasch item threshold map indicated that all but 1 item (suicidal ideation) were appropriately ordered. The 207 wave 2 participants were 74% females, 82% white, with a mean age of 45 years. The exploratory factor analyses resulted in a single component (all standardized factor loadings >0.46). Cronbach α was 0.93 and the 7-day test-retest intraclass correlation coefficient (n = 93) was 0.84 (95% confidence interval 0.77-0.89). SMDDS scores discriminated between MDD severity levels.

CONCLUSIONS:

The 16-item SMDDS generated highly reliable scores with substantial evidence of construct validity. On the basis of the evidence of appropriate content validity and sound psychometric performance, the Food and Drug Administration qualified the SMDDS as an outcome measure to support exploratory efficacy endpoints in MDD clinical trials.

KEYWORDS:

content validity; depression; major depressive disorder; patient-reported symptom measure

PMID:
31426932
DOI:
10.1016/j.jval.2019.02.010
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