Cost-effectiveness of colonoscopy in screening for colorectal cancer

Modelling A decision model based on a Markov process was used to model the total costs and effectiveness of the three screening strategies. The timeframe of each cycle was one year. The model referred to a hypothetical population of 100,000 persons aged 50 years. If the annual FOBT is negative, patients have to wait for the next annual test and if positive, patients are referred to colonoscopy. In the case of normal colonoscopy, annual FOBT is resumed after 10 years, while in the case of an adenomatous polyp, surveillance colonoscopy is repeated every 3 years until the adenomatous polyps disappear. For 5-year flexible sigmoidoscopy, the model is similar to that for FOBT. In the case of colonoscopy, the model is similar to the previous ones, except that all the states associated with a screening test other than colonoscopy are eliminated. Those patients who declined scheduled tests entered the state of non-compliance. Three types of noncompliance were considered: screened patients must be compliant with the initial procedure, each repeated screening, and colonoscopy after a positive result on FOBT or flexible sigmoidoscopy. Patients could move to the state of CRC in any cycle.