Psychometric properties of the Revised Illness Perception Questionnaire among Iranian parents of children with autism spectrum disorder

Abstract

Background The Revised Illness Perception Questionnaire (IPQ-R) has been adapted for the study of autism spectrum disorder (ASD), but its use has not been studied in Iran. In this study, we evaluated the psychometric properties of the Revised Illness Perception Questionnaire for Autism Spectrum Disorder (IPQ-R-ASD-Persian) and how Iranian parents’ perceptions of autism may be related to parental anxiety, depression, and affect. Method This study included 114 parents of children with ASD in Iran. A sociodemographic questionnaire, the IPQ-R-ASD-Persian, Generalized Anxiety Disorder-7, Patient Health Questionnaire-9, and Positive and Negative Affect Schedule were administered. Confirmatory factor analysis and the maximum likelihood method based on the variance-covariance matrix were employed to explore the IPQ-R-ASD factor structure. Four measures of goodness-of-fit were utilized, which included chi-square/degree of freedom (χ2/df), comparative fit index (CFI), root mean square error of approximation (RMSEA), and standardized root mean square residual (SRMR). Cronbach’s alpha and the corrected item-total correlation were used to measure internal consistency. The convergent validity was assessed by calculating the average variance extracted. Furthermore, we evaluated the test-retest reliability of the IPQ-R-ASD-Persian scales over two weeks using intra-class correlation coefficient (ICC). Results There was no floor or ceiling effect for the IPQ-R-ASD-Persian scales. Cronbach’s α values were consistently higher than 0.70, except for Timeline-Cyclical (α = 0.484). All scales of the IPQ-R-ASD-Persian except for the Timeline-Cyclical scale generally showed good test-retest reliability over two weeks. Confirmatory factor analysis indicated a seven-factor model (χ2/df = 1.62, CFI = 0.92, RMSEA = 0.064, SRMR = 0.098), similarly to the original IPQ-R instrument. Conclusions The IPQ-R-ASD-Persian demonstrated statistically acceptable reliability and validity levels supporting its use as a viable instrument for such research in Iran. As a result, this might be a useful approach for evaluating parents’ perceptions which is vital for supporting families and for developing effective interventions.