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

OBJECTIVE

Key psychometric information was sought for three newly derived dimensions from an abridged Illness Behaviour Questionnaire (IBQ-31): Affirmation of Illness (AI), Concern for Health (CH) and General Affective State (GAS). The construct validity of these scales was examined along with their test-retest reliability and long-term stability.

DESIGN

A longitudinal, observational study was conducted with 675 participants (general community members and those with either asthma, diabetes and chronic pain or chronic fatigue syndrome) providing self-report questionnaire data at baseline, with additional information sought at three (n = 483; 71.6%) and 12 months (n = 517, 76.6%).

MAIN OUTCOME MEASURES

Construct validity of the IBQ-31 was explored using well-validated psychological measures of Symptom Attributions and Symptom Experience, Cognitive Distortion of Somatic Information and Illness Likelihood.

RESULTS

In general, AI, CH and GAS shared predictable empirical overlap with related psychological indices across the five samples. Adequate three-month test-retest reliability was evident, with greater score variability over 12 months.

CONCLUSION

The IBQ-31 comprises three theoretically relevant dimensions which demonstrate relative short- and long-term stability for individuals with diverse illness experiences. Future investigations should explore the predictive validity of AI, CH and GAS, along with the potential value of 'cut-off' scores for clinical use.