Table 2. Effect of Screening Intervention on Surrogate Endpoints (e.g., Stage at Diagnosis and Adenoma Detection)
| Sigmoidoscopy [2,3] | FOBT/ Sigmoidoscopy [4,5] | Barium Enema [6] | Colonoscopy [7,8] | CT Colonography [9-11] | Stool DNA Mutation Tests [12] | Immunochemical FOBT | |
| CRC = colorectal cancer; CT = computed tomography; FOBT = fecal occult blood test; iFOBT = immunochemical fecal occult blood test; N/A = not available. | |||||||
| Study Design | Case-control studies | Randomized controlled studies | Ecologic and descriptive studies | Ecologic and descriptive studies | Ecologic and descriptive studies | Studies in progress | Cross-sectional study in which iFOBT is administered to persons receiving colonoscopy |
| Internal Validity | Poor | Fair | Fair | Fair | Fair | Unknown | Good |
| Consistency | Fair | Poor | Poor | Poor | Poor | Unknown | Good |
| 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 | iFOBT detects >60% and ≤90% of CRCs |
| External Validity | Poor | N/A | N/A | N/A | Poor | Unknown | N/A |
References
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