Research indicates lowering FIT positivity thresholds improves sensitivity, specificity comparable to mt-sRNA testing

Lowering the fecal immunochemical test (FIT) positive threshold yields levels of sensitivity and specificity that are comparable to those reported for multitarget stool RNA (mt-sRNA) testing without the additional testing, according to a research letter published June 1 in JAMA.

Tobias Niedermaier, Ph.D., from the German Cancer Research Center in Heidelberg, and colleagues examined whether lowering the FIT positivity threshold could achieve levels of sensitivity and specificity comparable to mt-sRNA testing, which incorporates a commercially available FIT, concentration of eight RNA transcripts, and participant-reported smoking status, without additional stool testing and smoking assessment.

The sensitivities of FIT for detecting colorectal cancer (CRC) or advanced adenoma and specificity for absence of advanced neoplasia were ascertained for FIT in the BLITZ study after lowering the positivity threshold to 8.8 µg/g, which yielded the same positivity rate as reported for the mt-sRNA test in the CRC-PREVENT study (17%). A total of 7,607 participants were included in the analyses.

The researchers found that lowering the FIT positivity threshold achieved similar sensitivities for CRC (94.9 versus 94.4%) and for advanced adenoma (44.7 versus 45.9%). Specificities were also similar (86.9 versus 85.5%).

"Future comparisons of novel stool-based screening tests with FITs should incorporate comparisons of sensitivities at the same positivity rate or specificity," the authors write.

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