Psychometric properties of the Persian version of the brief illness questionnaire in Iranian with non-specific chronic neck pain

Introduction: The Brief Illness Perception Questionnaire (BIPQ) is an instrument for assessing the illness perception. Illness perception varies between individuals based on their health status. There is no study that assess the psychometric properties of the Persian version of BIPQ in neck pain patients. The goal of this study was to evaluate the reliability, construct validity, and exploratory factor analysis of the Persian BIPQ in individuals with non-specific chronic neck pain.

Methods: This is a cross-sectional study in which 123 individuals with non-specific chronic neck pain participated. 60 participants examined after 7 days for testing reliability. Reliability was assessed by intra-class correlation coefficient, standard error of measurement, and minimal detectable change. For assessing construct validity and item-total correlation, correlation tests were used. Also, exploratory factor analysis was done to assess the factor structure of the BIPQ.

Results: Exploratory factor analysis' results showed that there were 2 factors with Eigenvalues >1. Factor 1 included "identity", "consequence", "timeline", and "emotional response". Factor 2 consisted of "coherence" and "treatment control". The intra-class correlation coefficient and the cronbach's alpha for the total score was 0.8 and 0.86 respectively. Results of correlation tests showed an acceptable construct validity except with SF-12 mental component. Item-total correlation tests demonstrated that the correlations were above 0.3 for all subscales except for "treatment control" and "coherence".

Conclusion: BIPQ has an acceptable properties to assess illness perception in individuals with non-specific chronic neck pain. The results of exploratory factor analysis and item-total correlation confirmed that 2-subscale version is more acceptable.