• Kevin Selby, Christopher D Jensen, Jeffrey K Lee, Chyke A Doubeni, Joanne E Schottinger, Wei K Zhao, Jessica Chubak, Ethan Halm, Nirupa R Ghai, Richard Contreras, Celette Skinner, Aruna Kamineni, Theodore R Levin, and Douglas A Corley.
• Kaiser Permanente Northern California, Oakland, California (K.S., C.D.J., J.K.L., W.K.Z., D.A.C.).
• Ann. Intern. Med. 2018 Oct 2; 169 (7): 439447439-447.

BackgroundThe fecal immunochemical test (FIT) is commonly used for colorectal cancer (CRC) screening. Despite demographic variations in stool hemoglobin concentrations, few data exist regarding optimal positivity thresholds by age and sex.ObjectiveTo identify programmatic (multitest) FIT performance characteristics and optimal FIT quantitative hemoglobin positivity thresholds in a large, population-based, screening program.DesignRetrospective cohort study.SettingKaiser Permanente Northern and Southern California.ParticipantsAdults aged 50 to 75 years who were eligible for screening and had baseline quantitative FIT results (2013 to 2014) and 2 years of follow-up. Nearly two thirds (411 241) had FIT screening in the previous 2 years.MeasurementsFIT programmatic sensitivity for CRC and number of positive test results per cancer case detected, overall and by age and sex.ResultsOf 640 859 persons who completed a baseline FIT and were followed for 2 years, 481 817 (75%) had at least 1 additional FIT and 1245 (0.19%) received a CRC diagnosis. Cancer detection (programmatic sensitivity) increased at lower positivity thresholds, from 822 in 1245 (66.0%) at 30 µg/g to 925 (74.3%) at 20 µg/g and 987 (79.3%) at 10 µg/g; the number of positive test results per cancer case detected increased from 43 at 30 µg/g to 52 at 20 µg/g and 85 at 10 µg/g. Reducing the positivity threshold from 20 to 15 µg/g would detect 3% more cancer cases and require 23% more colonoscopies. At the conventional FIT threshold of 20 µg/g, programmatic sensitivity decreased with increasing age (79.0%, 73.4%, and 68.9% for ages 50 to 59, 60 to 69, and 70 to 75 years, respectively; P = 0.009) and was higher in men than women (77.0% vs. 70.6%; P = 0.011).LimitationInformation on advanced adenoma was lacking.ConclusionIncreased cancer detection at lower positivity thresholds is counterbalanced by substantial increases in positive tests. Tailored thresholds may provide screening benefits that are more equal among different demographic groups, depending on local resources.Primary Funding SourceNational Cancer Institute.

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