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Canadian Journal of Gastroenterology
Volume 27, Issue 2, Pages 90-94
Original Article

Relationship between the Number of Positive Fecal Occult Blood Tests and the Diagnostic Yield of Colonoscopy

Ahmad Muinuddin, Ramona Aslahi, Wilma M Hopman, and William G Paterson

Gastrointestinal Diseases Research Unit, and the Department of Medicine, Queen’s University, Kingston, Ontario, Canada

Received 12 April 2012; Accepted 12 August 2012

Copyright © 2013 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


BACKGROUND: In 2007, Ontario launched a colon cancer screening program for average-risk individuals based on biennial fecal occult blood tests (FOBTs) on three fecal samples, followed by colonoscopy for individuals who tested positive.

OBJECTIVE: To determine whether >1 positive screening FOBT was predictive of finding advanced neoplasia at colonoscopy.

METHODS: A retrospective chart review of outpatient colonoscopic procedures performed at Hotel Dieu Hospital (Kingston, Ontario) in the first two years of the colon cancer screening program was conducted, focusing on endoscopic and pathological findings.

RESULTS: Of 5556 individuals undergoing colonoscopy, 346 were referred for positive FOBT. Overall, 41 (11.8%) patients with a positive FOBT had colon cancer. In 16 (4.6%) cases, the number of positive FOBTs was not reported. For the 330 individuals in whom the number of positive tests was specified, 198, 71 and 61 cases had one, two and three positive results, respectively. Cancer was found at colonoscopy in 11 (5.6%), 11 (15.5%) and 18 (29.5%) of individuals with one, two and three positive FOBT results, respectively (OR 3.0 [95% CI 1.2 to 7.3] and 6.5 [95% CI 2.8 to 15.0] for two or three positive FOBTs compared with one; P=0.015 and P<0.001, respectively). High-risk adenomas (>1 cm in diameter, villous component and/or high-grade dysplasia) were found in 41 (20.8%), 29 (42.0%) and 25 (41.0%) individuals with one, two and three positive FOBTs, respectively (OR 2.8 [95% CI 1.5 to 5.0] and 2.4 [95% CI 1.3 to 4.5] for two or three positive FOBTs compared with one; P=0.001 and P=0.006, respectively).

CONCLUSIONS: The diagnostic yield of colonoscopy varied directly with the number of positive FOBTs. This information may be useful in assigning scheduling priority for patients with positive FOBTs.