August 28, 2019
2 min read

Lower FIT threshold increases sensitivity for colorectal cancers

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Results of a meta-analysis revealed that using a fecal immunochemical test positivity threshold of 10 µg hemoglobin/g feces or less, rather than between 10 and 20 µg hemoglobin/g feces, can increase the sensitivity for detecting colorectal cancers by more than 10%.

Kevin Selby, MD, MAS, of the Center for Primary Care and Public Health at University of Lausanne in Switzerland, and colleagues wrote that the optimal FIT positivity cutoff is not known and can likely change based on many factors, including age and sex. It can also be adjusted to optimize CRC detection while taking local colonoscopy resources into account.

“Some experts in the United States favor a uniform threshold of [20 µg hemoglobin/g feces or less], but evidence is limited because individual studies included small numbers of patients with CRC; data and consistent definitions for advanced adenoma detection were frequently not included; variable comparison groups between studies; and variability between FIT brands and positivity thresholds,” they wrote.

Investigators searched the literature for studies that included FIT for CRC screening in asymptomatic adults so they could quantify the change in CRC and advanced adenoma detection at different positivity thresholds, as well as by age and sex. They calculated sensitivity and specificity at four different threshold ranges ( 10 µg hemoglobin/g feces; 10 to 20 µg/g; 20 to 30 µg/g; and > 30 µg/g).

Across 46 studies comprising 2.4 million individuals and 6,478 detected cancers, Selby and colleagues determined that sensitivity for detection of CRC increased from 69% (95% CI, 63%–75%) at a threshold between 10 µg hemoglobin/g feces and 20 µg hemoglobin/g feces to 80% (95% CI, 76%–83%) at 10 µg hemoglobin/g feces or less. Sensitivity for detection of advanced adenomas also increased from 21% (95% CI, 18%–25%) to 31% (95% CI, 27%–35%) at the same thresholds. However, specificity decreased from 94% to 91%.

In three studies stratified by sex, sensitivity for detection of CRC was 77% in men and 81% in women. In three studies stratified by ages, sensitivity for CRC detection was 85% for ages 50 to 59 years and 73% for ages 60 to 69 years.

Selby and colleagues wrote that their findings suggest that FIT positivity threshold as low as 10 µg hemoglobin/g feces or less could be considered preferable in settings that have sufficient resources for follow-up colonoscopies.

“Additional data are needed regarding the influence of sex and age on test performance,” they wrote. “Future research should determine the impact of quantitative thresholds of 10 µg/g with multiple rounds of annual testing and provide better estimates of FIT performance in important subgroups.” by Alex Young

Disclosures: The authors report no relevant financial disclosures.