Psychometric characteristics of the Revised Illness Perception Questionnaire (IPQ-R) in adults with sickle cell disease

OBJECTIVE: Sickle cell disease (SCD) is the most frequent monogenic disease worldwide. Psychological and behavioural factors are often reported as playing a significant role in predicting SCD health outcomes. When focusing on adaptation to a specific health condition and its treatment, the Common Sense Model of Health and Illness (CSM) has proven to be of heuristic value. In other health conditions, illness outcomes are directly influenced by illness perception. Therefore, the aim of this study is to explore the psychometric proprieties of the Revised Illness Perception Questionnaire (IPQ-R). DESIGN: We performed a cross-sectional assessment on 517 adult patients with sickle cell disease and collected the results of 406 IPQ-R. With these data, we verified the factor structure of the Belief scale and proposed modifications to improve its fit to the data with a confirmatory factor analysis. In addition, we explored the factorial structure of the Causal attribution scale with an exploratory factor analysis. RESULTS: The initial model showed poor fit with the data. After structural modifications, elimination of two items with a low loading (model 2), covariance added between items (model 3) and items reallocation (model 4), the last model proposed presented a correct fit with the data. Before doing this model specification, we reviewed and compiled the nine studies that explored the psychometric properties of the IPQ-R in order to highlight all the modifications made by the other authors who have adapted the IPQ-R to a specific population and to allow a comparison with our own modifications. CONCLUSION: Considering previous findings, this research suggests further work is needed on the structure of the dimensions of the IPQ-R.