Development and psychometric properties of a short form of the Illness Denial Questionnaire

Background: Coping with chronic illness can be overwhelming for patients and caregivers, and may be inhibited by the denial mechanism, and therefore, denial represents a critical issue for health professionals. Assessing illness denial is far from easy, and brief tools suitable for medical settings are lacking. In this paper, the development of a short form of the Illness Denial Questionnaire (IDQ) for patients and caregivers is presented. Methods: In study 1, the IDQ was administered to 118 patients and 83 caregivers to examine the internal structure of denial; then the properties of the items (DIF, fit, and difficulty) were evaluated according to the Rasch model in order to select the best items for the Illness Denial Questionnaire-Short Form (IDQ-SF). Study 2 included 202 participants (113 patients and 89 caregivers). The internal structure of the IDQ-SF was tested via confirmatory factor analysis (CFA). Reliability and concurrent validity were also studied using the Anxiety and Depression Questionnaire-Reduced Form (AD-R). Results: The CFA showed a two-factor structure encompassing "Denial of negative emotions" and "Resistance to change". Results of the Rasch analyses led to the selection of 4 items for each dimension. The resulting IDQ-SF (8 items) showed a two-factor structure as well as good reliability and concurrent validity with AD-R. Conclusion: The IDQ-SF represents a valid tool for quickly evaluating the core of illness denial in patients and caregivers. This brief and easily administrable questionnaire allows health professionals to outline the presence and severity of illness denial in order to set individually tailored interventions.