Fecal Immunochemical Test Detects Sessile Serrated Adenomas and Polyps With a Low Level of Sensitivity

The serrated pathway is a distinct pathway of colorectal carcinogenesis that has been implicated in development of a substantial proportion of interval colorectal cancers. The fecal immunochemical test (FIT) detects early neoplasms with a higher level of sensitivity than the guaiac test. We investigated the sensitivity of the FIT in detection of sessile serrated adenomas/polyps (SSA/Ps).

We performed a prospective study of 6198 asymptomatic subjects (mean age, 59.0 ± 7.0 years) who received concurrent screening colonoscopies and FITs at the Health Management Center of National Taiwan University Hospital from August 2010 through November 2014. The sensitivity of FIT for conventional adenoma, advanced adenoma, and SSA/P at different cutoffs was calculated, and results were compared by using multivariate analysis adjusted for potential confounders.

Prevalence values of SSA/P, adenoma, and advanced adenoma were 1.4%, 20.2%, and 5.5%, respectively. At cutoffs of 10, 15, and 20 μg hemoglobin/g feces, the FIT detected all SSA/Ps with 12.3%, 6.2%, and 6.2% sensitivity, large SSA/Ps with 18.4%, 10.5%, and 10.5% sensitivity, and advanced adenomas with 32.4%, 24.5%, and 20.9% sensitivity, respectively. Multivariate analysis revealed that positive results from the FIT did not differ significantly between individuals with SSA/P and those with non-advanced adenoma or those with negative findings from colonoscopy. Patients with large SSA/Ps were less likely to have positive results from the FIT than patients with advanced adenoma, with odds ratios of 0.44 (95% confidence interval [CI], 0.18-1.05), 0.30 (95% CI, 0.10-0.90), and 0.37 (95% CI, 0.12-1.12) at cutoffs of 10, 15, and 20 μg hemoglobin/g feces, respectively, after adjusting for lesion size, even with synchronous conventional adenoma.

In a prospective study of 6198 subjects receiving the FIT and colonoscopy, we found that the FIT detected SSA/Ps with significantly lower levels of sensitivity than conventional adenoma. Further studies are needed to determine the effects of these findings on the effectiveness of FIT-based colorectal cancer screening program.