Detecting and Explaining Aberrant Responding to the Outcome Questionnaire-45.

Area of Science:

• Psychometrics
• Clinical Psychology
• Psychiatry

Background:

• Patient-reported outcome measures (PROMs) are crucial for monitoring treatment progress.
• Aberrant responding can compromise the validity of PROM data.
• Person-fit analysis (PFA) is a statistical method to detect unusual response patterns.

Purpose of the Study:

• To investigate the prevalence and predictors of aberrant responding using PFA on the Outcome Questionnaire-45 (OQ-45).
• To examine if clinical diagnosis influences the likelihood of person misfit.
• To assess the suitability of general outcome measures across different patient groups.

Main Methods:

• Applied item response theory (IRT) based PFA to OQ-45 data from Dutch clinical outpatients.
• Utilized the chi-squared person-fit statistic to identify misfitting response patterns.
• Employed logistic regression to predict person misfit based on clinical diagnosis, OQ-45 total score, and Global Assessment of Functioning (GAF).

Main Results:

• The chi-squared statistic identified 12.6% of response patterns as misfitting.
• Person misfit demonstrated a positive association with psychological distress severity.
• Patients with psychotic, somatoform, or substance-related disorders showed higher rates of misfit compared to mood and anxiety disorder patients.

Conclusions:

• General outcome measures like the OQ-45 may not be universally appropriate for all patient diagnoses.
• Detecting person misfit is essential for accurate interpretation of patient outcomes in clinical settings.
• Clinical practice should incorporate PFA to ensure data validity and appropriate patient assessment.