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. 2021 Jul;33(7):610-618.
doi: 10.1037/pas0001009. Epub 2021 May 31.

Developing a common metric for depression across adulthood: Linking PROMIS depression with the Edinburgh Postnatal Depression Scale

Courtney K Blackwell  1 , Xiaodan Tang  1 , Amy J Elliott  2 , Tracy Thomes  2 , Hannah Louwagie  2 , Richard Gershon  1 , Benjamin D Schalet  1 , David Cella  1
Affiliations

Developing a common metric for depression across adulthood: Linking PROMIS depression with the Edinburgh Postnatal Depression Scale

Courtney K Blackwell et al. Psychol Assess. 2021 Jul.

Abstract

Depression is a leading mental health concern across the U.S. and worldwide. There are myriad assessments to evaluate depressive symptoms, including the Edinburgh Postnatal Depression Scale (EPDS), which is widely used to evaluate women's pre- and postnatal depression but not as prevalent at other timepoints in adulthood, limiting its utility for longitudinal research. As part of the National Institutes of Health's (NIH) Environmental influences on Child Health Outcomes (ECHO) Research Program, the current study sought to develop a common metric so that scores on the EPDS can be converted to the standardized Patient-Reported Measurement Information System (PROMIS®) T-score metric. Drawing on data from the ECHO-Prenatal Alcohol in SIDS and Stillbirth cohort, this study used a single-group linking design, where 1,263 mothers completed the EPDS and PROMIS-Depression measures at the same time. Score linking was conducted using equipercentile and item response theory (IRT) methods. Results showed both linking methods provide robust, congruent results, and subgroup invariance held across age, race, ethnicity, education, and geographic location. The IRT-based unidimensional fixed-parameter calibration was selected due to its model simplicity, and a crosswalk table was established to convert scores from the EPDS to PROMIS T-scores. Overall, this study provides a way to aggregate data across various depression measures and timepoints, such that researchers and clinicians now have the ability to directly compare and combine EPDS data with PROMIS and other depression measures already score-linked to PROMIS. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

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Conflict of interest statement

The authors have no conflicts of interest relevant to this article to disclose.

Figures

Figure 1
Figure 1. Test Information Function of Each Instrument Using Linked Item Parameters and the Combined Scale
Note. PROMIS Depression = the eight-item PROMIS Depression Short Form 8a; EPDS = Edinburgh Postnatal Depression Scale. See the online article for the color version of this figure.
Figure 2
Figure 2. IRT Crosswalk-Linking Function (Based on Fixed-Parameter Calibration) and Equipercentile Functions With Different Levels of Smoothing
Note. PROMIS Depression = the eight-item PROMIS Depression Short Form 8a; EPDS = Edinburgh Postnatal Depression Scale; EQP = equipercentile; SM = postsmoothing. See the online article for the color version of this figure.
Figure 3
Figure 3. Bland—Altman Plot for the IRT Pattern Scoring Approach and the IRT Crosswalk Scoring Approach
Note. See the online article for the color version of this figure.
See this image and copyright information in PMC

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