gms | German Medical Science

Background: Large bowel endoscopy with removal of polyps strongly reduces colorectal cancer (CRC) risk. In epidemiological studies, ascertainment of large bowel endoscopies often relies on self-reports and might be prone to imperfect recall.

Methods: We assessed the validity of self-reported colorectal endoscopies in a population-based case-control study from Germany including 540 cases with histologically confirmed incident CRC and 614 control persons (DACHS study). We sought to obtain all medical records for the last self-reported endoscopy and for a subsample of 100 subjects reporting no previous endoscopy, and calculated odds ratios (ORs) of CRC risk according to self-reports and medical records.

Results: In total, 377 of 483 medical records for the last self-reported colorectal endoscopy could be obtained (78%). Sensitivity of self-reports was 100% and specificity ranged from 93-99% among subgroups defined by age, gender, education, family history of CRC, and case-control status. Adjusted OR (95% confidence interval) for CRC risk after previous colonoscopy was 0.31 (0.21-0.45) using self-reports and 0.31 (0.20-0.47) using medical records. However, agreement between self-reports and medical records was poor regarding type of endoscopy (colonoscopy, sigmoidoscopy or rectoscopy; kappa=0.22), moderate concerning polypectomy (kappa=0.58), and reasonable for year of examination (kappa=0.70).

Conclusions: Self-reports of previous colorectal endoscopies agreed well with medical records. However, validation appears to be essential with respect to details of the examination.