Flexible sigmoidoscopy following a positive faecal occult blood test within a bowel screening programme may reduce the detection of neoplasia.
OBJECTIVE
Colorectal cancer screening using the faecal occult blood test (FOBt) detects a disproportionate number of left-sided tumours. This study aims to examine the theoretical impact on neoplasia detection rates of a sigmoidoscopy-first protocol in FOBt-positive patients undergoing colonoscopy.


METHODS
From retrieved endoscopy/pathology reports, pathology up to and including the splenic flexure was assumed detectable by sigmoidoscopy. High-risk polyps prompting subsequent colonoscopy were classed as three or more polyps, one polyp of ≥ 1 cm, villous or tubulovillous components or the presence of high-grade dysplasia.


RESULTS
Between April 2009 and April 2011, 4631 patients underwent colonoscopy as a result of a positive FOBt in Greater Glasgow and Clyde. Cancer was detected in 398 (9%) and adenomas were detected in 1985 (47%) of which 1323 (67%) were deemed significant according to British Society of Gastroenterology guidelines. Applying the flexible sigmoidoscopy-first model, cancer would have been detected in 329 (8%) patients and adenomas in 1640 (39%), of which 1140 (70%) would have been significant. In total, 1546 (37%) patients would have required subsequent colonoscopy, following which 21 patients would have a new diagnosis of cancer. The positive predictive values (PPVs) for neoplasia (47 vs 57%, P < 0.001), significant neoplasia (35 vs 41%, P < 0.001) and cancer (8 vs 9%, P = 0.007) were all lower in the sigmoidoscopy-first model.


CONCLUSIONS
A significant reduction in the detection of both adenomas and cancers would be seen if the sigmoidoscopy-first protocol were to be used following a positive FOBt. Furthermore, a significant proportion of patients would be subjected to two procedures, with considerable implications for both the patient and cost.
Academic Department of Surgery, School of Medicine, Royal Infirmary, University of Glasgow, Glasgow, UK.
D
D
Mansouri
D C
DC
McMillan
C S D
CS
Roxburgh
S J
SJ
Moug
E M
EM
Crighton
P G
PG
Horgan
D000230:Adenocarcinoma / Q000175:diagnosis*; D000236:Adenoma / Q000175:diagnosis*; D000368:Aged; D003113:Colonoscopy / Q000706:statistics & numerical data*; D015179:Colorectal Neoplasms / Q000175:diagnosis*; D055088:Early Detection of Cancer / Q000379:methods / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009780:Occult Blood; D011237:Predictive Value of Tests; D012812:Sigmoidoscopy / Q000706:statistics & numerical data*
Colorectal cancer; FIT; colonoscopy; flexible sigmoidoscopy; gFOBt; screening