Assessing the impact of a single qualitative fecal immunochemical test on colonoscopy prioritization and mortality in risk-stratified patients with suspected colorectal cancer: a retrospective cohort study.

Background: Performing fecal immunochemical tests in symptomatic individuals at low-or moderate risk for suspected colorectal cancer could help prioritize candidates for colonoscopies. The objective of this study was to assess the diagnostic accuracy of the fecal immunochemical test (FIT) in symptomatic individuals at low-or moderate risk of colorectal cancer and explore association with survival. Methods: We conducted a retrospective cohort study between December 2016 and July 2024 from a single-center, public hospital in Chile. Adults (≥18 years-old) individuals were included, those with symptoms suggestive of colorectal cancer and set for evaluation via colonoscopy. Symptomatic individuals with suspected colorectal cancer were stratified as high risk or low/moderate risk by a trained nurse according to 2015 NICE guidelines. Subsequently, high risk patients were directly referred for colonoscopies, while low/moderate risk patients underwent a single qualitative FIT and prioritized to colonoscopy based on results. Main outcomes were FIT diagnostic accuracy for colorectal cancer, overall mortality, and colorectal cancer-specific mortality. Findings: A total of 394 out of 1304 participants (30%) were classified as high risk. The remaining 910 (70%) were categorized as low/moderate risk and were referred for FIT. From these, 808 (89%) individuals were tested and had results for FIT. Regarding the diagnostic accuracy of the FIT, sensitivity was 96% and specificity reached 66.8%, with a negative value of 99.8%. Low/moderate risk positive FIT (FIT+) and high-risk participants had higher mortality rates vs. low/moderate risk negative FIT (FIT-) individuals. Time-to-event analysis confirmed a lower cumulative mortality in low/moderate risk FIT- patients. A multivariable Cox regression model showed a consistently lower risk of death in this group, while a non-significant trend towards increased mortality was observed in low/moderate risk FIT+ individuals after 30 months. Interpretation: In symptomatic individuals at low or moderate risk, a single qualitative FIT was associated with high sensitivity and moderate specificity for colorectal cancer detection. FIT may help prioritize colonoscopy in low-resource settings, but further prospective validation is warranted. Funding: This research was partially funded by ANIDFONDAP152220002 (CECAN).