Factorial validity and invariance of four psychosocial constructs of colorectal cancer screening: does screening experience matter?

BACKGROUND Few studies have examined the psychometric properties and invariance of scales measuring constructs relevant to colorectal cancer screening (CRCS). We sought to: (i) evaluate the factorial validity of four core constructs associated with CRCS (benefits, barriers, self-efficacy, and optimism); and (ii) examine measurement invariance by screening status (currently screened, overdue, never screened). METHODS We used baseline survey data from a longitudinal behavioral intervention trial to increase CRCS among U.S. veterans. Respondents were classified as currently screened (n = 3,498), overdue (n = 418), and never screened (n = 1,277). The measurement model was developed using a random half of the sample and then validated with the second half of the sample and the full baseline sample (n = 5,193). Single- and multi-group confirmatory factor analysis was used to examine measurement invariance by screening status. RESULTS The four-factor measurement model demonstrated good fit. Factor loadings, item intercepts, and residual item variance and covariance were invariant when comparing participants never screened and overdue for CRCS, indicating strict measurement invariance. All factor loadings were invariant among the currently screened and overdue groups. Only the benefits scale was invariant across current screeners and never screeners. Non-invariant items were primarily from the barriers scale. CONCLUSION Our findings provide additional support for the construct validity of scales of CRCS benefits, barriers, self-efficacy, and optimism. A greater understanding of the differences between current and never screeners may improve measurement invariance. IMPACT Measures of benefits, barriers, self-efficacy, and optimism may be used to specify intervention targets and effectively assess change pre- and post-intervention across screening groups.