The expanding role of Fecal Immunochemical Test (FIT) in the early detection of colorectal cancer

Colorectal cancer (CRC) remains one of the most preventable yet deadly forms of cancer, largely due to missed opportunities in early detection. Despite the existence of effective screening tools, CRC continues to cause approximately 935,000 deaths worldwide each year, ranking as the second most common cause of cancer-related mortality.

The gap between what is possible and what is practiced underscores an urgent need for more widespread and optimized screening strategies. As a recent P.A.C.E^.® and ACCENT^® accredited webinar hosted by SelectScience^® emphasizes, clinical laboratories are central to this transformation.

Sally C. Benton Biochemistry Services Clinical Lead and Consultant Clinical Scientist in Biochemistry, Berkshire and Surrey Pathology Services, and Royal Surrey County Hospital and Director, NHS Bowel Cancer Screening Hub, for the South of England delivers the session with a clear focus: Empower labs to adopt fecal immunochemical testing (FIT) not just as a test, but as a linchpin in a more intelligent and efficient approach to colorectal cancer screening.

“FIT is not new, but its significance in population-based and symptomatic testing has grown substantially,” Benton says. “We now understand how to implement it in more flexible and tailored ways, allowing us to reduce unnecessary colonoscopies while increasing early cancer detection.”

Tailoring screening strategies beyond one size FITs all

Benton opens with a stark look at CRC’s burden. In the UK, she notes, CRC is the fourth most common cancer and the second leading cause of cancer death. Yet, when detected early, five-year survival rates can exceed 90 percent. The problem lies in access and follow-through. Colonoscopy remains the gold standard, but it is invasive, costly, and resource intensive. “We need to use colonoscopy wisely,” she says, “because it’s not feasible to offer it to everyone with a low-risk profile.”

FIT offers a pragmatic alternative. It detects human hemoglobin in stools with much higher sensitivity and specificity than the older guaiac-based fecal occult blood test (gFOBT). Crucially, it provides quantitative results, allowing laboratories and clinicians to establish thresholds that reflect patient risk and service capacity.

“You can set different cut-offs based on the clinical question,” Benton explains. “In symptomatic patients, we might use a cut-off of 10 µg/g, but in screening programs we often use thresholds that match available resources and acceptable positive predictive values.” This adaptability makes FIT more than just a tool; it becomes a strategic filter that helps triage patients efficiently.

Tackling preanalytical variability

Despite its promise, FIT is only as reliable as the system that supports it. One of the main challenges Benton addresses is variability in the preanalytical phase, particularly patient sample collection. Because FIT relies on a single stool sample collected by the patient at home, inconsistencies in collection methods, timing, and storage can skew results.

“Preanalytical variability is probably our biggest Achilles' heel,” Benton notes. “We have to educate patients properly and ensure patient kits are user-friendly and stable under real-world conditions.”

Stability of hemoglobin in stools is affected by temperature and time. Benton highlights studies showing that samples can degrade, leading to false negatives. Her lab has implemented a policy of processing samples within seven days and encouraging patients to return them promptly.

Education plays a vital role too. “We’ve worked hard to develop clear instructions for patients,” she says. “Simple things like visual guides, translations, or in-person explanations can dramatically improve return rates and sample integrity.”

Analytical considerations for thresholds and quality control

While preanalytical factors are often overlooked, analytical integrity is equally critical. FIT’s value lies in its quantitative nature, but interpreting those numbers requires context.

“The choice of threshold is not trivial,” Benton says. An acceptable cut-off should be established at the facility. “A cut-off of 10 µg/g might identify more cancers but could overload endoscopy services with false positives. A higher threshold reduces strain but risks missing early-stage disease.”

This trade-off must be weighed carefully, especially in settings with limited capacity. Benton emphasizes that labs must work in close collaboration with clinical teams to agree on acceptable thresholds, taking into account epidemiology, resource constraints, and patient outcomes.

Equally important is robust quality assurance. Sally Benton discusses external quality assessment (EQA) schemes availability and challenges. There are some available for FIT, and Benton recommends that labs participate in these schemes to monitor performance and comparability across sites.

“FIT is more than just plugging a cartridge into a machine,” she says. “It requires rigorous internal QC and participation in external QA to maintain reliability over time.”

Integrating FIT into clinical pathways

The webinar also addresses how FIT data should be used in clinical decision-making. One of the most effective applications, Benton explains, is in symptomatic patients who do not meet urgent referral criteria for colonoscopy. FIT allows general practitioners to make more informed decisions about who needs further investigation.

“In primary care, we’ve seen how FIT can reduce unnecessary referrals and ensure high-risk patients are prioritized,” she says. “It’s a win for both patients and the system.”

She presents data from the National Health Service (NHS) that shows significant reductions in colonoscopy demand without compromising cancer detection rates. In fact, targeted use of FIT has been associated with improved stage distribution at diagnosis, with more cancers detected at earlier, more treatable stages.

“The more we learn to trust the negative predictive value of FIT, the more we can use it confidently to reassure patients,” Benton adds.

Future directions and ongoing challenges

As testing technologies evolve, the role of the lab continues to expand. Benton notes that molecular stool testing and biomarker panels may eventually complement or refine current FIT-based strategies. However, implementation hurdles remain.

“There’s still a lot of skepticism, particularly around missing cancers with low bleeding,” she acknowledges. “But when used correctly, FIT is a powerful triage tool that can drive system-wide improvement.”

She encourages labs to engage with national screening programs, contribute to data collection efforts, and advocate for fit-for-purpose infrastructure, including better digital reporting tools and automated systems.

“Success depends on integration,” she says. “The test itself is only part of the puzzle. We need end-to-end processes that connect the lab, the clinic and the patient.”

As CRC rates are projected to rise globally due to aging populations and lifestyle risk factors, early detection remains the most effective strategy for reducing mortality. The evidence presented in the webinar makes it clear: with thoughtful implementation, FIT can be a cornerstone of this strategy.

To learn more, and earn CPD credits, watch the full webinar on demand.