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.

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Introduction:The Knee Injury and Osteoarthritis Outcome Score-Physical Function Short-form and the Patient-Reported Outcomes Measurement Information System Physical Function are widely used patient-reported outcome measures in orthopaedic practice and research. It would be helpful for clinicians and researchers to compare scores obtained on one instrument with those collected on another. To achieve this goal, this study conducted a linking analysis and computed a crosswalk table between these two scales. Data: The data of this study were collected as part of the clinical care of total knee arthroplasty patients in a large urban and suburban health system. The sample was a mix of responses from nonsurgical (no surgery performed), preoperative (before surgical intervention), and postoperative (after surgical intervention) groups. Methods: This study applied five linking methods: the item response theory (IRT)-based linking methods including fixed-parameter calibration, separate-parameter calibration with Stocking-Lord constants, and calibrated projection; and the equipercentile methods with log-linear smoothing and nonsmoothing approaches. Before conducting the linking analysis, we checked the linking assumptions including the similar content of the two scales, the unidimensionality of the combined scales, and the population invariance. The results of the five linking methods were evaluated by mean difference, SD, root-mean-squared deviation, intraclass correlation coefficient of the observed T scores and the crosswalkderived T scores. Results: The linking assumptions were all met. T scores generated from the Stocking-Lord crosswalk had the smallest mean difference (= 20.03) and relatively small SD (= 4.91) and root-mean-squared deviation (= 4.91) among the five linking methods. We validated this crosswalk in a larger sample with the nonsurgical, preoperative, and postoperative groups and in an external sample.