Measurement properties of the Illness Perception Questionnaire in practitioners working with patients with co-morbid schizophrenia and learning disability

Rationale, aims and objectives: The widely-used Illness Perception Questionnaire (IPQ) adapted for use in patients with major mental health problems and those who care and work with them, was originally developed for evaluating the illness perceptions of patients with physical pathology. There have been concerns expressed regarding the appropriateness of the IPQ and derivative measures of it in axis I disorders such as schizophrenia. The current investigation examined the measurement characteristics of a modified version of the IPQ in mental health practitioners working with patients with schizophrenia co-morbid with learning disability.  Method: Two hundred and ten mental health practitioners working with patients with schizophrenia co-morbid with learning disability participated in the study. Contemporary models of the measurement structure of the IPQ were evaluated using confirmatory factor analysis. The internal reliability of the IPQ was also evaluated. Results: Single factor, 5-factor and 6-factor models were evaluated against data. All models were found to offer a poor fit to the data. The internal reliability of the measure was also found to be unsatisfactory overall.  Conclusions: Consistent with one previous study that has found poor measurement characteristics of the IPQ when used in the context of schizophrenia, the current study found the measure to be a poorly performing index of illness perceptions. Echoing previous observations of the use of this tool in axis I disorder, it is recommended that a new measure of illness perceptions be developed using contemporary research methodology sensitive to the context of psychotic illness in order to provide a more effective tool for the provision of person-centered psychiatry and healthcare.