National Meeting 2008

1074 — Validation of Self-Reported Colorectal Cancer Screening Behavior Data Collected from a Mixed-mode Survey of Veterans

Grill J (Minneapolis Center of Excellence (COE)) , Noorbaloochi S (Minneapolis COE & University of Minnesota), Powell AA (Minneapolis COE & University of Minnesota), Burgess DJ (Minneapolis COE & University of Minnesota), Vernon SW (University of Texas - Houston), Halek K (Minneapolis COE), Griffin JM (Minneapolis COE & University of Minnesota), van Ryn M (University of Minnesota), Fisher DA (Durham VAMC and Duke University)

Objectives:
Self-report is a critical source of information on CRC screening adherence but can be misleading if it is not sufficiently valid. This study assessed the validy of self-reported colorectal cancer (CRC) screening behavior data collected from a sample of veterans.

Methods:
890 patients age 50-75 from the Minneapolis Veterans Affairs Medical Center were surveyed by mail using standard questions developed by the National Cancer Institute. Phone administration was attempted with mail non-responders. VA and non-VA records were combined for the referent standard. Sensitivity, specificity, concordance and report-to-records ratio (R2R) were estimated for overall and test-specific CRC adherence among respondents providing complete medical records. Secondary analyses examined variation in estimates by patient characteristics, treatment of missing and uncertain responses, and whether a strict or liberal time interval was used for assessing concordance.

Results:
Complete medical records were available for 345 of the 686 survey responders. For overall adherence, sensitivity was 0.98, specificity 0.59, concordance 0.88, and R2R 1.14. Sensitivity was 0.82 for fecal occult blood test (FOBT), 0.75 for sigmoidoscopy, 0.97 for colonoscopy, and 0.62 for double contrast barium enema (DCBE). Specificity was 0.89 for FOBT, 0.76 for sigmoidoscopy, 0.72 for colonoscopy, and 0.85 for DCBE. Concordance was > 0.80 for all tests other than sigmoidoscopy (0.75). R2R was 1.31 for FOBT, 1.34 for sigmoidoscopy, 1.42 for colonoscopy, and 6.0 for DCBE. The R2R decreased using a combined sigmoidoscopy and colonoscopy measure. Over-reporting was more pronounced for older, less educated individuals with no family history of colorectal cancer. Sensitivity and R2R improved using a liberal interval and treating uncertain responses as non-adherent (versus missing), but differences were not statistically significant.

Implications:
Self-reported CRC screening validity is generally acceptable and robust across definitional decisions, but varies by screening test and patient characteristics.

Impacts:
The variation in the validity of self-reported CRC screening behaviors across screening tests and patient subgroups found in this study could limit comparability across studies and bias inferences about subgroup differences in screening behavior within studies. Future variation studies relying on self-reported CRC screening measures should confirm that validity does not vary significantly across subgroups.