Validation of self-reported history of colorectal cancer screening

Shariq Khoja, S Elizabeth McGregor, Robert J Hilsden
Canadian Family Physician M├ędecin de Famille Canadien 2007, 53 (7): 1192-7

OBJECTIVE: This study aims to determine the validity of self-reported history of colorectal cancer (CRC) testing consisting of fecal occult blood tests (FOBTs)in the past 2 years or endoscopy (flexible sigmoidoscopy or colonoscopy) in the past 5 years by comparing it with reports provided by physicians.

DESIGN: A cross-sectional design was used for this study.

SETTING: Study participants were selected directly from the city's population. Self-reported history of CRC testing was validated using records obtained from their physicians' offices.

PARTICIPANTS: Participants were adults of 50 to 74 years, living within the boundaries of Calgary Health Region in Alberta.

INTERVENTIONS: Participants were recruited by a random-digit dial telephone survey of adults aged 50 to 74 years (n = 598). Following a phased process, a subset of these people (n = 200) agreed to provide names of their physicians to be contacted for their histories of CRC testing. Physicians' reports were used to measure validity of self-reported history.

MAIN OUTCOME MEASURES: Agreement between self-reported history and physician's records was measured using kappa statistics and concordance. Validity of self-report was measured by calculating sensitivity, specificity, positive predictive values, and negative predictive values. Reasons for testing reported by the participants were compared with those reported by their physicians.

RESULTS: Complete information was received for 146 participants, revealing a 34.2% testing rate for CRC. Intermediate level of agreement for testing history (kappa = 0.66 and concordance = 84.9%) was found between the 2 types of reporting for CRC testing. Self-reported history showed sensitivity of 76.0% (95% CI = 61.8%-86.9%) and specificity of 89.6% (95% CI = 81.7%-94.9%). High specificity was also observed for self-reporting of the individual tests, but low sensitivity was seen for the reporting of FOBT in the last 2 years. Most participants who correctly recalled the testing history also accurately identified the reason for testing (concordance = 80.0% for FOBT and 69.6% for endoscopy).

CONCLUSION: Self-reported history of CRC testing and physicians' reports showed dependable agreement. Physicians need to probe their patients further for the history of FOBT. These results can be useful in clinical practice to determine the CRC screening status of the patients.

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