Sigmoidoscopy [1,2]	FOBT/ Sigmoidoscopy [3,4]	Barium Enema [5]	Colonoscopy [6,7]	CT Colonography [8-10]	Stool DNA Mutation Tests [11]
CT = computed tomography; FOBT = fecal occult blood test.
Study Design	Case-control studies	Randomized controlled studies	Ecologic and descriptive studies	Ecologic and descriptive studies	Ecologic and descriptive studies	Studies in progress
Internal Validity	Poor	Fair	Fair	Fair	Fair	Unknown
Consistency	Fair	Poor	Poor	Poor	Poor	Unknown
Magnitude of Effects on Surrogate Endpoints	About 45% decrease in detection rate of cancers compared with colonoscopy	No difference in diagnostic yield between sigmoidoscopy + FOBT vs. sigmoidoscopy alone	Barium enema detects about 30%–50% of cancers detected by colonoscopy	About 3% of patients with no distal adenomas have advanced proximal neoplasia. There is a threefold increase in this rate in patients with distal adenomas.	CT colonography may have similar sensitivity to colonoscopy in certain centers.	Unknown
External Validity	Poor	N/A	N/A	N/A	Poor	Unknown

References

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2. Schoenfeld P, Cash B, Flood A, et al.: Colonoscopic screening of average-risk women for colorectal neoplasia. N Engl J Med 352 (20): 2061-8, 2005.  [PUBMED Abstract]
   
   
3. Segnan N, Senore C, Andreoni B, et al.: Randomized trial of different screening strategies for colorectal cancer: patient response and detection rates. J Natl Cancer Inst 97 (5): 347-57, 2005.  [PUBMED Abstract]
   
   
4. Gondal G, Grotmol T, Hofstad B, et al.: The Norwegian Colorectal Cancer Prevention (NORCCAP) screening study: baseline findings and implementations for clinical work-up in age groups 50-64 years. Scand J Gastroenterol 38 (6): 635-42, 2003.  [PUBMED Abstract]
   
   
5. Winawer SJ, Stewart ET, Zauber AG, et al.: A comparison of colonoscopy and double-contrast barium enema for surveillance after polypectomy. National Polyp Study Work Group. N Engl J Med 342 (24): 1766-72, 2000.  [PUBMED Abstract]
   
   
6. Lieberman DA, Weiss DG, Bond JH, et al.: Use of colonoscopy to screen asymptomatic adults for colorectal cancer. Veterans Affairs Cooperative Study Group 380. N Engl J Med 343 (3): 162-8, 2000.  [PUBMED Abstract]
   
   
7. Imperiale TF, Wagner DR, Lin CY, et al.: Risk of advanced proximal neoplasms in asymptomatic adults according to the distal colorectal findings. N Engl J Med 343 (3): 169-74, 2000.  [PUBMED Abstract]
   
   
8. Pickhardt PJ, Choi JR, Hwang I, et al.: Computed tomographic virtual colonoscopy to screen for colorectal neoplasia in asymptomatic adults. N Engl J Med 349 (23): 2191-200, 2003.  [PUBMED Abstract]
   
   
10. Mulhall BP, Veerappan GR, Jackson JL: Meta-analysis: computed tomographic colonography. Ann Intern Med 142 (8): 635-50, 2005.  [PUBMED Abstract]
    
    
11. Imperiale TF, Ransohoff DF, Itzkowitz SH, et al.: Fecal DNA versus fecal occult blood for colorectal-cancer screening in an average-risk population. N Engl J Med 351 (26): 2704-14, 2004.  [PUBMED Abstract]