Development and psychometric validation of the intermittent self-catheterization questionnaire

Intermittent catheterization, often performed by the users themselves and known as intermittent self-catheterization (ISC), has become the gold standard treatment for people with chronic urinary retention. To date, there are no validated patient-reported outcome measures for individuals who rely on ISC that focus on ISC-related quality of life and can help health care professionals and catheter users to optimize long-term ISC care.

The objective of this study was to develop and validate a patient-reported outcome measure, the Intermittent Self-Catheterization Questionnaire (ISC-Q), which evaluates aspects of quality of life specific to the needs of individuals performing ISC.

This study was divided into 2 phases. The first phase focused on the development of the ISC-Q using 20 interviews and a review of selected literature. In addition, 10 interviews with UK and French individuals who performed ISC were conducted to ensure face and content validity of the ISC-Q. In the second phase of the study, the ISC-Q was administered online in the United Kingdom, France, and Germany to 306 individuals with neurologic urinary retention (including spinal cord injury, multiple sclerosis, and spina bifida), who performed ISC for at least 6 months, and were aged 18 to 85 years. Item reduction, reliability, and validity testing were performed to determine the psychometric properties of the ISC-Q. Responsiveness and minimum important differences were also examined.

The initial phase of the study led to the development of a 4-domain instrument focusing on ease of use, convenience, discreetness, and psychological well-being. Various item reduction techniques were used that resulted in the removal of 3 items from the ISC-Q; there were 24 items in the final version. The conceptual framework of the ISC-Q was confirmed with a four-factor solution of the subscales. The ISC-Q was psychometrically robust, with excellent internal consistency, adequate test-retest reliability, and good validity (convergent and known groups validity). Overall, the responsiveness results show the ISC-Q to be sensitive to change, and the total ISC-Q minimum important difference estimates ranged from 4.94 to 8.73.

The findings illustrate the ISC-Q to be a valid and reliable outcome measure that evaluated aspects of ISC-related quality of life.