Table 4--Summary of Different CRC Screening Modalities
| Modality | Evidence | Strengths | Weakness | Future Considerations |
| Fecal occult blood testing | 3 controlled randomized trials | Simple Low-cost Non-invasive |
Poor sensitivity & specificity Poor compliance |
Immunologic detection of human blood DNA stool studies |
| Flexible Sigmoidoscopy | Case-controlled studies Randomized trials pending |
Direct visualization & removal of polyps | Only partial evaluation of colon | Risk-stratification of distal polyp for follow-up colonoscopy |
| Combined flexible sigmoidoscopy and FOBT | Screening colonoscopy study suggests only small increased sensitivity | FOBT evaluates whole colon and complements partial evaluation from flexible sigmoidoscopy | No direct evidence even though most cost-efficient in an analysis [Frazier,2000] | |
| Colonoscopy | Effectiveness extrapolated from National Polyp Study and study of screening colonoscopy | Examines the whole colon and allows prevention of CRC by polyp removal | Costly and invasive No direct evidence |
Training endoscopist Optimal time interval & one-time colonoscopy |
| Barium enema | By extrapolation | Examines whole colon | Poor sensitivity No direct evidence |
Virtual colonoscopy |