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Cancer Epidemiol Biomarkers Prev. 2019 Sep 5. doi: 10.1158/1055-9965.EPI-18-1368. [Epub ahead of print]

False-Positive Results in a Population-Based Colorectal Screening Program: Cumulative Risk from 2000 to 2017 with Biennial Screening.

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Cancer Prevention and Control Programme, Catalan Institute of Oncology, L'Hospitalet de Llobregat, Barcelona, Spain.
Gastroenterology Department, Bellvitge University Hospital, L'Hospitalet de Llobregat, Barcelona, Spain.
Colorectal Cancer Group, ONCOBELL Programme, Bellvitge Biomedical Research Institute Hospitalet de Llobregat, Barcelona, Spain.
Consortium for Biomedical Research in Epidemiology and Public Health (CIBEResp), Barcelona, Spain.
Cancer Prevention and Control Programme, Catalan Institute of Oncology, L'Hospitalet de Llobregat, Barcelona, Spain.
Cancer Prevention and Control Group, IDIBELL Programme, Bellvitge Biomedical Research Institute, Hospitalet de Llobregat, Barcelona, Spain.
Department of Biostatistics, Epidemiology & Informatics, University of Pennsylvania, Philadelphia, Pennsylvania.



The aim of this study was to estimate the cumulative risk of a false-positive (FP) result in a fecal occult blood test (FOBT) through 7 screening rounds and to identify its associated factors in a population-based colorectal cancer screening program.


Retrospective cohort study, which included participants ages 50 to 69 years of a colorectal cancer screening program in Catalonia, Spain. During this period, 2 FOBTs were used (guaiac and immunochemical). A discrete-time survival model was performed to identify risk factors of receiving a positive FOBT with no high-risk adenoma or colorectal cancer in the follow-up colonoscopy. We estimated the probability of having at least 1 FP over 7 screening rounds.


During the period of 2000 to 2017, the cumulative FP risk was 16.3% (IC95%: 14.6%-18.3%), adjusted by age, sex, and type of test. The median number of screens was 2. Participants who began screening at age 50 years had a 7.3% [95% confidence interval (CI), 6.35-8.51] and a 12.4% (95% CI, 11.00-13.94) probability of an FP with 4 screening rounds of guaiac-based test and immunochemical test, respectively. Age, the fecal immunochemical test, first screening, and number of personal screens were factors associated with an FP result among screenees.


The cumulative risk of an FP in colorectal screening using FOBT seems acceptable as the colonoscopy, with its high accuracy, lengthens the time until additional colorectal screening is required, while complication rates remain low.


It is useful to determine the cumulative FP risk in cancer screening for both advising individuals and for health resources planning.

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