Fecal occult blood testing when colonoscopy capacity is limited

Fecal occult blood testing (FOBT) can be adapted to a limited colonoscopy capacity by narrowing the age range or extending the screening interval, by using a more specific test or hemoglobin cutoff level for referral to colonoscopy, and by restricting surveillance colonoscopy. Which of these options is most clinically effective and cost-effective has yet to be established.

We used the validated MISCAN-Colon microsimulation model to estimate the number of colonoscopies, costs, and health effects of different screening strategies using guaiac FOBT or fecal immunochemical test (FIT) at various hemoglobin cutoff levels between 50 and 200 ng hemoglobin per mL, different surveillance strategies, and various age ranges. We optimized the allocation of a limited number of colonoscopies on the basis of incremental cost-effectiveness.

When colonoscopy capacity was unlimited, the optimal screening strategy was to administer an annual FIT with a 50 ng/mL hemoglobin cutoff level in individuals aged 45-80 years and to offer colonoscopy surveillance to all individuals with adenomas. When colonoscopy capacity was decreasing, the optimal screening adaptation was to first increase the FIT hemoglobin cutoff value to 200 ng hemoglobin per mL and narrow the age range to 50-75 years, to restrict colonoscopy surveillance, and finally to further decrease the number of screening rounds. FIT screening was always more cost-effective compared with guaiac FOBT. Doubling colonoscopy capacity increased the benefits of FIT screening up to 100%.

FIT should be used at higher hemoglobin cutoff levels when colonoscopy capacity is limited compared with unlimited and is more effective in terms of health outcomes and cost compared with guaiac FOBT at all colonoscopy capacity levels. Increasing the colonoscopy capacity substantially increases the health benefits of FIT screening.