Reducing positivity threshold also increased number of positive test results per cancer case
FRIDAY, Sept. 21, 2018 (HealthDay News) — Programmatic sensitivity for colorectal cancer (CRC) detection increases modestly with decreasing fecal immunochemical test (FIT) positivity thresholds, according to a study published online Sept. 18 in the Annals of Internal Medicine.
Kevin Selby, M.D., from Kaiser Permanente Northern California in Oakland, and colleagues identified programmatic (multitest) FIT performance characteristics and optimal FIT quantitative hemoglobin positivity thresholds among adults aged 50 to 75 years who were eligible for screening. A total of 640,859 individuals completed baseline quantitative FIT (2013 to 2014) and were followed for two years.
The researchers found that 75 percent of participants had at least one additional FIT and 0.19 percent received a diagnosis of CRC. At lower positivity thresholds, there was an increase in cancer detection, from 66 percent at 30 µg/g to 74.3 percent at 20 µg/g and 79.3 percent at 10 µg/g; there was also an increase in the number of positive test results per cancer case detected, from 43 to 52 and 85 at 30, 20, and 10 µg/g, respectively. Three percent more cancer cases would be detected and 23 percent more colonoscopies would be required by reducing the positivity threshold from 20 to 15 µg/g. Programmatic sensitivity decreased with increasing age at the conventional FIT threshold of 20 µg/g, and it was higher in men than women.
“Increased cancer detection at lower positivity thresholds is counterbalanced by substantial increases in positive tests,” the authors write.
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