A recent review in the Annals of Internal Medicine compared 31 studies on at-home colorectal cancer (CRC) tests called fecal immunochemical test (FIT) for sensitivity and found that they are just as effective for colorectal cancer screening in "average-risk" people as a colonoscopy. The team found that single-application FITs have moderate to high sensitivity and specificity for CRC.
Example of a common endoscope. Photo source: Wikipedia Commons
These screens vary in their testing methods, with some using a guaiac-based fecal occult blood test (gFOBT) while others use the fecal immunochemical test (FIT) for human globulin. The authors of the study chose to look only at FITs, for, according to lead author, Dr. Thomas F. Imperiale, MD, of the Indiana University School of Medicine, a FIT "is more sensitive and specific than guaiac-based fecal occult blood testing for CRC and advanced adenomas". The review included studies which compared FIT results to a colonoscopy, the "gold standard" for detecting CRC today.
The authors also included studies that varied by FIT threshold. FITs are marketed products from private companies which typically analyze the results themselves. For quantitative data, they look at the amount of hemoglobin in the stool and have a cut-off, or threshold, which is used to determine a "positive" or "negative" result. For example, if their threshold is 20 µg/g, a sample with a higher concentration than 20 µg/g it is labeled "positive". The reviewers grouped studies based on thresholds into five groups (<10, 10, >10 to <20, 20, and >20 µg/g).
Eighteen FITs were tested, with individual studies testing 1 to 6 FITs. The authors found that the specific threshold provided by the FIT kit was related to the sensitivity of the result. Studies comparing FITs with a <10 µg/g were more likely to detect hemoglobin than those with higher thresholds. However, the higher the sensitivity, the higher the false-positive rate. The authors conclude that, because FITs vary in terms of thresholds, which could mediate the false-positive rate, health care systems need to consider the quantity and quality of data for a specific FIT, including the thresholds for each one.
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At-home kits to test for CRC are more convenient, private, and less invasive than a colonoscopy. They are less cost prohibitive and, as this review suggests, may be just as accurate as a colonoscopy. Only sixty-five percent of Americans aged 50 to 75 years have been tested using any method for CRC. Better education for both patients and clinicians alike is needed to increase the percentage of adults aged 50 to 75 years getting screened. FITs could help recruit more adults because it is simple, can be done at home, and accurate. Most importantly, the message needs to get out that a FIT is not "second-best" compared to the colonoscopy. The results of such a campaign could increase the percentage of adults being screened for CRC to 80% by some accounts. And this will ultimately lead to early detection of CRC in more people.
Sources: Annals of Internal Medicine, MedLinePlus.gov, ccalliance.gov