Clinical Edge

Summaries of Must-Read Clinical Literature, Guidelines, and FDA Actions

FIT Performance & Optimal Positivity Thresholds

Ann Intern Med; ePub 2018 Sep 18; Selby, et al

Among adults screened for colorectal cancer (CRC) using the fecal immunochemical test (FIT), increased cancer detection at lower positivity thresholds was counterbalanced by substantial increases in positive tests, indicating that tailored thresholds may provide screening benefits. The community-based cohort study included adults aged 50-75 years who were eligible for screening and had baseline quantitative FIT results (2013 and 2014) and 2 years of follow-up. Nearly two-thirds of participants (n=411,241) had FIT screening in the previous 2 years. Measurements included FIT programmatic sensitivity for CRC and number of positive test results per cancer case detected, overall, and by age and sex. Researchers found:

  • Of 640,859 persons who completed a baseline FIT and were followed for 2 years, 481,817 (75%) had at least 1 additional FIT and 1,245 (0.19%) received a CRC diagnosis.
  • Cancer detection increased at lower positivity thresholds; the number of positive test results per cancer case detected also increased.
  • Reducing the positivity threshold from 20 to 15 µg/g would detect 3% more cancer cases and require 23% more colonoscopies.


Selby K, Jensen CD, Lee JK, et al. Influence of varying quantitative fecal immunochemical test positivity thresholds on colorectal cancer detection: A community-based cohort study. [Published online ahead of print September 18, 2018]. Ann Intern Med. doi:10.7326/M18-0244.