Pros and cons of the three main screening modalities
| Faecal occult blood (unhydrated, Haemoccult) | Flexible sigmoidoscopy | Colonoscopy | |
|---|---|---|---|
| CRC, colorectal cancer; FOB, faecal occult blood; FS, flexible sigmoidoscopy. | |||
| Setting | Home | OPD endoscopy | Endoscopy |
| Bowel prep | No (diet restriction possible) | Self admin enema | Full bowel prep |
| Sedation | No | No | Yes |
| Staff | Tester | Nurse | Physician, nurse, pathologist |
| Duration of procedure | — | 5 minutes. Longer in novices | 15–20 minutes. Longer in novices |
| Day off work | No | No | Yes |
| Success rate | Predictive value for CRC of positive FOB: 5–10%31 | 2% return due to inadequate bowel prep32 | Completion rate in 79% of all cases33 |
| Sensitivity for cancers or polyps > 1 cm | Cancers 50%,31 polyps 17–46%34 | 95% cancer and high risk polyps35 | 95% cancer and high risk polyps35 |
| Specificity for cancers or polyps > 1 cm | Cancers 98%31 | 100%36 | 100%36 |
| Cost (1999) of individual test | $5 (2001),37 £14.338 | $99 (2001)37; £96 (1998)39 | $380 (2001)37 £138 (1998)39 |
| Incremental cost effectiveness ratios compared with no screening (per year of life saved) 1998 | $12 6673 $970540 (annual non hydrated FOB) | $16 7863 (annual non-hydrated FOB plus FS every 5 years) | $20 418,3 $10 98340 (colonoscopy every 10 years) |
| Therapeutic (ability to remove polyps) | No | No | Yes (increases cost slightly) |
| Large intestine visualised | Ability to screen right sided pathology | Rectum, sigmoid colon, and possibly descending colon | Whole large intestine |