Construct validity and temporal stability of the abridged 31-item Illness Behaviour Questionnaire

Area of Science:

• Psychometrics
• Health Psychology
• Behavioral Medicine

Background:

• The Illness Behaviour Questionnaire (IBQ-31) is an abridged version of a widely used measure.
• Three new dimensions were derived: Affirmation of Illness (AI), Concern for Health (CH), and General Affective State (GAS).
• Assessing the psychometric properties of these new dimensions is crucial for their application.

Purpose of the Study:

• To determine the construct validity, test-retest reliability, and long-term stability of the AI, CH, and GAS dimensions of the IBQ-31.
• To evaluate the psychometric properties of these scales in diverse patient populations.
• To provide key psychometric information for the IBQ-31's newly derived dimensions.

Main Methods:

• A longitudinal, observational study with 675 participants from general community and clinical samples (asthma, diabetes, chronic pain, chronic fatigue syndrome).
• Self-report questionnaire data collected at baseline, 3 months, and 12 months.
• Construct validity assessed using established measures of symptom attributions, experience, cognitive distortion, and illness likelihood.

Main Results:

• The AI, CH, and GAS dimensions showed expected relationships with related psychological measures across samples.
• Adequate test-retest reliability was observed at the three-month follow-up.
• Greater score variability was noted over the 12-month period, indicating reduced long-term stability.

Conclusions:

• The IBQ-31's three dimensions (AI, CH, GAS) are theoretically relevant and demonstrate reasonable short-term stability.
• The scales show relative stability across diverse illness experiences.
• Future research should investigate the predictive validity and clinical utility of cut-off scores for AI, CH, and GAS.