Sensitivity of Faecal Occult Blood Testing for Asymptomatic Colorectal Cancer and Advanced Adenomas Over a 25-Year Experience in Colorectal Cancer Screening
Authors: Macrae, F.A., Slattery, M.A., Brown, G.J., O'Dwyer, M.A., Murphy, C.G., Hibbert, M.E. and St John, D.J.
Journal: Journal of Gastroenterology and Hepatology (2005); 20 (Suppl.): A34
Abstract:
The performance characteristics of FOBT for asymptomatic (AS) colorectal cancer and advanced adenomas is uncertain. Sensitivity, for example, requires direct comparison with a gold standard such as colonoscopy or, less accurately, close follow-up of a cohort of negative screenees to detect interval cancers. Our aim is to assess the sensitivity, specificity and predictive values for neoplasia of FOBT in a cohort of AS moderate and high risk subjects undergoing scheduled colonoscopy.
Methods: 4821 registrants had 5398 colonoscopies since the programme started in 1979. A cohort of 893 AS patient episodes with planned colonoscopies and a preceding FOBT within 3 months were analysed for sensitivity, specificity and predictive value for neoplasia of FOBT.
Results: 5 cancers were detected, with 3 being FOBT positive. There were 49 AS advanced adenomas, of which 17 (34.7%) were positive, and 148 episodes with detection of any neoplasia, of which 38 (25.7%) were FOBT positive. Specificity for advanced adenomas or cancers was 85.9ő (95% Confidence Interval, 83.4%-88.2%) and the predictive value for a positive FOBT for any neoplasia was 27.5% (20.4% to 35.9%). The likelihood ratio for detection of an advanced adenoma or cancer was 2.6 (1.8 to 3.9).
Conclusion: These results show that FOBT identifies a sub-group of at-risk but AS people enriched with colorectal neoplasia, and support the need for colonoscopy surveillance in this population. This study also supports introduction of FOBT-based screening for average risk subjects, however, results should be interpreted in the light of our population being above-average risk.
| FOBT Results |
Colonoscopy Findings | ||||
|---|---|---|---|---|---|
| Normal | Adenoma | Advanced Adenoma | Carcinoma | TOTAL | |
| Negative | 645 | 76 | 32 | 2 | 755 |
| Positive | 100 | 18 | 17 | 3 | 138 |
| Total | 745 | 94 | 49 | 5 | 893 |
© 2005 Journal of Gastroenterology and Hepatology Foundation and Blackwell Publishing Asia Pty Ltd