(RxWiki News) The gold standard for detecting colorectal cancer is the colonoscopy, which provides an internal view of the entire colon. At home fecal sample tests are also available, but how accurate are they?
The at-home fecal immunochemical test, or FIT, accurately detects 79 percent of colorectal cancers, a review of previous studies found.
And the overall diagnostic accuracy of FITs is 95 percent.
"Talk to your doctor about different colorectal cancer screening methods."
A team of researchers, led by Jeffrey K. Lee, MD, in the Division of Gastroenterology with the University of California, San Francisco, identified and analyzed data from studies involving thousands of people to quantify the accuracy of FITs in detecting the presence or absence of colorectal cancer.
Colorectal cancer will be diagnosed in nearly 143,000 Americans this year, and the disease will be the cause of death of almost 51,000 people in this country.
There are several ways to screen for colorectal cancer. In addition to internal exams, two types of at-home tests are available that examine fecal samples for blood that may suggest colorectal cancer (CRC).
Fecal occult blood occult tests (FOBTs) look for occult, or tiny spots of blood hidden in the stool. Before taking this test, people are required to change their diet and stop certain medications. According to the study authors, FOBTs are linked to a 15 to 33 percent decrease in colorectal cancer (CRC) deaths. The accuracy of the test remains unclear, though, and the FOBT needs to be taken annually, something not all patients consistently do.
The FIT requires no changes in diet or medication intake, costs less than $25 and is easy to complete at home. Like the FOBT, the FIT looks for hidden blood in the stool. There are a number of different kinds of FITs, requiring different numbers of stool samples and having different cut-off measurements that indicate potential cancer.
FIT kits are sold under various brand names including OCMicro, FlexSure, HemeSelect and others.
If either the FOBT or FIT comes back positive, a colonoscopy is performed to confirm or dispute the test findings.
Dr. Lee and team analyzed the data from 19 studies, conducted between 1996 and 2013, which were designed to measure the effectiveness of the FIT in accurately detecting CRC.
The researchers looked at both FIT sensitivity, which shows a correct positive result for when disease is actually present, and specificity, which shows a correct negative result for disease that is not present. Overall accuracy of the test was also assessed.
Investigators discovered that the FIT was fairly sensitive, accurately detecting an average of 79 percent of CRCs with one round of testing.
The FIT was also highly specific, accurately showing negative results for 94 percent of people who did not have CRC.
Overall accuracy of FITs was 95 percent, according to Dr. Lee’s team.
Most FITs were performed with only one stool sample; tests requiring two or three samples were not more accurate than those requiring only one.
Sensitivity was greater when cut-off values (a positive result measure) were lower.
“Fecal immunochemical tests are moderately sensitive, are highly specific, and have high overall diagnostic accuracy for detecting CRC. Diagnostic performance of FITs depends on the cutoff value for a positive test result,” the researchers concluded.
"This study shows that the FIT test is a very good screening test for colon cancer. It is cheap, easy for everyone to do and accurate in diagnosing colon cancer." said Dr. Subhakar "Sub" Mutyala, Associate Director of the Baylor Scott & White Cancer Institute and Associate Professor at Texas A&M College of Medicine in Temple, Texas.
"The next step will be to see how widespread will be the usage of FIT and ultimately, if the earlier detection of cancer will decrease deaths from colon cancer," Dr. Mutyala told dailyRx News.
This study was published February 3 in the Annals of Internal Medicine.
Primary funding came from the National Institute of Diabetes and Digestive and Kidney Diseases and National Cancer Institute. No conflicts of interest were disclose