Robert H. Fletcher, MD, MSc
Which method of screening for colorectal cancer (guaiac-based fecal occult blood testing [gFOBT], immunochemical FOBT [FIT], or flexible sigmoidoscopy [FS]) has the highest participation and detection rates?
Randomized controlled trial.
To colonoscopy in participants with a positive screen result.
Population-based study in the Netherlands.
15 011 randomly selected residents 50 to 74 years of age. 670 randomized individuals (4.5%) who met the exclusion criteria (history of inflammatory bowel disease or colorectal cancer; colonoscopy, sigmoidoscopy, or barium contrast enema in ≤ 3 y; or major health problems), moved away, or died were excluded from the analysis.
After being randomized, participants were invited by mail to participate in the study. Participants assigned to gFOBT (n = 5004) or FIT (n = 5007) received the appropriate test kit, and those assigned to FS (n = 5000) were asked to schedule an appointment at the screening unit. The gFOBT involved collecting samples from 3 consecutive bowel movements (without dietary restrictions or medication limitations) and returning the kit by mail. The FIT involved collecting 1 fecal sample and returning the kit by mail. FS involved administration of an enema and sigmoidoscopy at a dedicated screening center.
Participation rate (per eligible invitee), screen positive rate (per screenee with a complete screen), detection rate (cases of advanced neoplasia [colorectal cancer or advanced adenomas] per screenee with a complete screen), and diagnostic yield (cases of advanced neoplasia per 100 eligible invitees).
96% (intention-to-treat analysis).
The Table shows the results. The diagnostic yield per 100 invitees was 2.4 for FS, 1.5 for FIT, and 0.6 for gFOBT (P < 0.001 for each pairwise comparison). Within each type of screening test, participation rates varied by age, sex, socioeconomic status, and urban/rural residence.
For colorectal cancer screening, flexible sigmoidoscopy had a lower participation rate but higher cancer detection rate than the 2 fecal occult blood tests (FOBTs). Both rates were higher with immunochemical FOBT than with guaiac-based FOBT.
Comparison of 3 methods of colorectal cancer screening†
†FIT = immunochemical fecal occult blood testing (FOBT), FS = flexible sigmoidoscopy, gFOBT = guaiac-based FOBT; CI defined in Glossary. Relative risk and CI calculated from data in article.
‡Patients with a positive screening test were referred for colonoscopy. FS: polyp ≥ 1 cm; ≥ 3 adenomas; ≥ 20 hyperplastic polyps; or histopathology showing villous adenoma, high-grade dysplasia, or invasive cancer. FIT: ≥ 100 mg hemoglobin/mL. gFOBT: ≥ 1 panel positive.
§Calculated from odds ratios in article that were adjusted for age and sex.
Fletcher RH. Immunochemical FOBT had higher participation and detection rates than guaiac-based FOBT for colorectal cancer screening. Ann Intern Med. 2010;152:JC6–2. doi: 10.7326/0003-4819-152-12-201006150-02002
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Published: Ann Intern Med. 2010;152(12):JC6-2.
Cancer Screening/Prevention, Colorectal Cancer, Gastroenterology/Hepatology, Gastrointestinal Cancer, Hematology/Oncology.
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Print ISSN: 0003-4819 | Online ISSN: 1539-3704
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