Evaluating Colorectal Cancer Screening Strategies (Immunological Test vs Biochemical Test) in Catalonia, Spain 2008-2010

Abstract

Background: The aim of this study was to evaluate the screening strategy (quantitative immunological test vs biochemical test) in a popu-lation-based screening program for colorectal cancer (CRC) in Catalonia. Methods: The fourth round of a screening program for CRC with a fecal occult blood test was implemented in Hospitalet de Llobregat during 2008-2010. A biochemical test was offered to 50,227 individuals and a quantitative immunological test was offered to 12,707 individuals. We analysed differences according to the screening strategy in the following variables: acceptability of the target population (participation, dropouts, and adherence to colonoscopy), diagnostic accuracy (positive predictive value and detection rates), results (size and location of lesions, staging of CRC) and resources (number of colonoscopies needed and time interval between the positive test and colonoscopy). Results: Participation was higher among individuals who used the immunological test (OR: 1.35; CI95%:1.27-1.42). Detection rates for adenomas and cancer were also higher for the immunological test, hightlighting the detection rate for high-risk adenomas (26.7‰ vs. 3.0‰). The positive predictive value for high-risk adenomas was 45.0% and 46.9% in the immunological test and guaiac test, respectively. The number of colonoscopies needed to detect cancer with the immunological test was almost two-fold than those needed with the guaiac test (13.6 vs 7.4). Conclusions: The immunological test is a good screening strategy particularly sensitive for detecting high-risk adenomas. However, it is paramount to have enough resources to assure the quality of the CRC screening due to the large number of colonoscopies that would be required.