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Eva Ørnbøl

Screening for depression: Rasch analysis of the structural validity of the PHQ-9 in acutely injured trauma survivors

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  • Kaj Sparle Christensen
  • Eva Oernboel
  • Doug Zatzick, Department of Psychiatry and Behavioral Sciences, University of Washington School of Medicine, Seattle, WA, USA
  • ,
  • Joan Russo, Department of Psychiatry and Behavioral Sciences, University of Washington School of Medicine, Seattle, WA, USA

OBJECTIVE: The Patient Health Questionnaire (PHQ-9) is widely used for screening of depression in acutely injured trauma survivors. Rasch analysis has been used to evaluate its measurement characteristics. This paper aims: 1) to assess the psychometric properties of the nine PHQ-9 items and 2) to determine the structural validity of using the total PHQ-9 score as a clinical outcome measure.

METHODS: PHQ-9 data for 937 persons aged 18-60years admitted to 20 level 1 trauma centers in the United States were included. Good model fit indicates that all items contribute to a single underlying trait.

RESULTS: Item 2 demonstrated misfit to the Rasch model, and six items showed disordered response categories. Ordered response categories were achieved for all nine items after modifying the original four-point scoring system into a three-point system. Person separation reliability was acceptable (0.80) for discriminating between groups of patients. Dimensionality testing supported combining the nine items into a total score. No significant differential item functioning was observed for sex and age group.

CONCLUSION: Despite some minor problems with its measurement structure, the short nine-item version of the PHQ seems to be an economic and valid instrument for the screening of depression in adults admitted to level 1 trauma centers.

Original languageEnglish
JournalJournal of Psychosomatic Research
Volume97
Pages (from-to)18-22
Number of pages5
ISSN0022-3999
DOIs
Publication statusPublished - Jun 2017

    Research areas

  • Journal Article

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