Fecal Immunochemical Test Detects Cancer and Polyps

The most commonly used noninvasive test for colorectal cancer (CRC) screening has been the guaiac fecal occult blood test (gFOBT). The fecal immunochemical test (FIT) detects CRC and colorectal polyps with higher levels of sensitivity than the gFOBT, and may be more acceptable to patients.

The fecal immunochemical test (FIT), has shown to be more sensitive for CRC and colorectal polyps and may be more acceptable to patients because FIT can often be done with one sample, instead of three, and does not require dietary restrictions, such as meat avoidance. Screening can reduce incidence and mortality of CRC, but is often underused.

Scientists at the Veterans Administration San Diego Healthcare System (VASDH, San Diego, CA, USA) conducted a retrospective observational study of 7,898 patients, 50–75 years old, who were offered stool-based CRC screening as part of primary care March 2014 through January 2015. The team performed manual reviews of colonoscopy and pathology reports for veterans with positive results from the tests. The primary outcome was test completion within one year of order; secondary outcomes were positive results and detection of advanced neoplasia by diagnostic colonoscopy. The primary analysis used an intention-to-screen approach, which included all patients with test orders; as-screened analyses were also performed.

Before July 2014, when noninvasive CRC screening was offered, a three-sample Hemoccult Sensa gFOBT test was distributed at point of primary care and returned either by mail or in person. From July to August 2014, VASDHS transitioned to using a one-sample FIT (Polymedco OC auto 80, Cortland, NY, USA), also returned either by mail or in person. Colonoscopy and pathology reports were specifically reviewed to ascertain presence of any advanced neoplasia. Advanced neoplasia in this analysis included any CRC or advanced adenoma.

The investigators obtained 4,662 FIT orders and 3,236 gFOBT orders. In the intention to screen analysis, a significantly higher proportion of subjects completed a FIT (42.6%) than a gFOBT (33.4%). Advanced neoplasia was detected in a significantly higher proportion of subjects offered a FIT (0.79%) than a gFOBT (0.28%). The numbers needed to invite to achieve one additional completed test and identify one additional patient with advanced neoplasia were 11 and 196, respectively. The investigators estimate that for every 1,000 tests, FIT would yield 51 colonoscopies, compared with 42 for gFOBT.

Samir Gupta, MD, MSCS, AGAF, the study’s senior and corresponding author and a staff physician, said, “Many physicians are unaware of the difference between FIT and gFOBT, and potential advantages. One of our hopes is that the paper and other associated literature will help laboratory directors and primary care physicians to realize that making a simple switch could have big benefits for patients.” The study was published in the August 2017 issue of the journal Clinical Gastroenterology and Hepatology.