The Barriers to Bowel Cancer Screening Scale: Examining Structural Validity, Measurement Invariance, and Criterion Validity.

Abstract

The success of national cancer screening programs, such as the National Bowel Cancer Screening Program (NBCSP) in Australia, depends on public participation, which is currently an alarming 43.5% for the NBCSP. Understanding the barriers that impede screening participation requires valid measurement instruments. This study aims to cross-validate such an instrument with a new, large, and varied sample, as well as assess measurement invariance across subsamples at a greatest risk of nonparticipation (ie, testing whether the scale functions in similar ways across groups). A cross-sectional sample of 1158 participants from the target screening population (50-74 years) provided demographic information, responses to the Barriers to Home Bowel Screening (BB-CanS) scale, and information on their previous screening participation. Both the full and the brief versions of the BB-CanS scale showed good model fit for the full sample and for gender and age subsamples. Despite the inter-factor correlations being high, the unidimensional and bi-factor models exhibited poorer fit. Improvement in fit was observed with scale refinement involving the removal of 7 items. All versions of the BB-CanS scale were invariant across gender and age subsamples. Age and gender differences emerged across several barriers and variance in all 4 barriers significantly predicted prior screening participation. The BB-CanS scale is a valid measure of 4 highly correlated barriers to home bowel cancer screening: disgust relating to screening, avoidance of test outcomes, practical difficulty (or challenges), and the need for a sense of greater autonomy. All versions of the instrument measure the equivalent construct across age and gender groups. Observed differences in barriers across at-risk groups provide targets for future intervention.