Journal of Gastroenterology and Hepatology (2001) 16, 389–392 people over 50 years of age who seek advice on screen- ing. Flexible sigmoidoscopy screening may also be offered on a 5-yearly basis. The requirement for repeat flexible sigmoidoscopy is unclear, and it has been suggested that 10-yearly repeat intervals may also be appropriate. 4,5 A positive FOBT or flexible sigmoidoscopy-proven adenoma or cancer requires further evaluation with colonoscopy.Whichever screen- ing modality is applied, colonoscopy remains the final common denominator in all screening programs. The resultant workload will need to be managed by an already ‘stressed’ health-care system, and it is critical for the success of CRC screening that the impact of these INTRODUCTION The Australian Health Technology Advisory Commit- tee has published a report into colorectal cancer (CRC) screening in Australia. 1 Its conclusion was that general population screening for CRC ‘in the Australian setting shows sufficient promise to warrant exploration through the establishment of pilot and feasibility studies’. National guidelines for the prevention, early detection and management of CRC were released in 1999 by the National Health and Medical Research Council. 2,3 These guidelines recommend fecal occult blood testing (FOBT) at least every second year for asymptomatic COLORECTAL CANCER SCREENING Fecal occult blood and flexible sigmoidoscopy screening for colorectal cancer: Modeling the impact on colonoscopy requirements and cancer detection rates JOHN K OLYNYK,* CAMERON F PLATELL † AND JUDITH A COLLETT ‡ Departments of *Medicine and † Surgery, University of Western Australia and ‡ Department of Gastroenterology, Fremantle Hospital, Fremantle,Western Australia, Australia Abstract Aim: The aim of this study was to estimate the colonoscopy requirements and the likely impact of fecal occult blood and flexible sigmoidoscopy screening on the detection of colorectal cancer by using pre- viously published data. Methods: Fecal occult blood and flexible sigmoidoscopy screening programs were applied to the 2.04 million subjects aged 50–65 years, at a participation rate of 40%. The following strategies were evalu- ated: Fecal occult blood testing with colonoscopy follow up of all positive tests; flexible sigmoidoscopy with colonoscopy follow up of all adenomatous polyps; and flexible sigmoidoscopy with colonoscopy follow up of all adenomatous polyps > 10 mm in size. Results: The fecal occult blood program detected 5.6% of all colorectal cancer cases at a rate of 2914 colonoscopies/percentage of detection of colorectal cancer. The flexible sigmoidoscopy program detected 14% of all colorectal cancer cases at a rate of 8160 colonoscopies/percentage of detection of colorectal cancer. The flexible sigmoidoscopy program with follow up of adenomatous polyps > 10 mm in size detected 13% of all colorectal cancer cases at a rate of 1230 colonoscopies/percentage of detec- tion of colorectal cancer. Conclusions: Flexible sigmoidoscopy screening followed by colonoscopic follow up of adenomatous polyps > 10 mm in size is the most efficient screening strategy in terms of colonoscopies generated and cases of colorectal cancer detected. © 2001 Blackwell Science Asia Pty Ltd Key words: colonoscopy, colorectal cancer, fecal occult blood test, flexible sigmoidoscopy, screening. Correspondence: Assoc. Prof. JK Olynyk, University Department of Medicine, Fremantle Hospital, PO Box 480, Fremantle 6959, Western Australia, Australia. Email: jolynyk@cyllene.uwa.edu.au Accepted for publication 6 December 2000.