Detecting and Explaining Aberrant Responding to the Outcome Questionnaire–45

Judith M. Conijn*, Wilco H.M. Emons, Kim De Jong, Klaas Sijtsma

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review


We applied item response theory based person-fit analysis (PFA) to data of the Outcome Questionnaire-45 (OQ-45) to investigate the prevalence and causes of aberrant responding in a sample of Dutch clinical outpatients. The (Formula presented.) person-fit statistic was used to detect misfitting item-score patterns and the standardized residual statistic for identifying the source of the misfit in the item-score patterns identified as misfitting. Logistic regression analysis was used to predict person misfit from clinical diagnosis, OQ-45 total score, and Global Assessment of Functioning code. The (Formula presented.) statistic classified 12.6% of the item-score patterns as misfitting. Person misfit was positively related to the severity of psychological distress. Furthermore, patients with psychotic disorders, somatoform disorders, or substance-related disorders more likely showed misfit than the baseline group of patients with mood and anxiety disorders. The results suggest that general outcome measures such as the OQ-45 are not equally appropriate for patients with different disorders. Our study emphasizes the importance of person-misfit detection in clinical practice.

Original languageEnglish
Pages (from-to)513-524
Number of pages12
Issue number4
Publication statusPublished - 21 Aug 2015
Externally publishedYes


  • aberrant responding
  • item response theory
  • outcome measurement
  • Outcome Questionnaire–45
  • person-fit analysis


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