Meta-Analysis Finds Home-Based Test Effective for Colorectal Cancer Screening

Tests that require patients to collect a single stool sample at home and then send it to a lab for analysis detect about 79% of colorectal cancers (CRCs), according to a new evidence review now published by Lee, et al. in the journal Annals of Internal Medicine, February 4, 2014. The review of 19 studies examining eight different fecal immunochemical tests (FITs) also finds that such tests will correctly identify about 94% of patients who do not have cancers of the rectum or colon. "Now we also know that [FIT] is a great tool for assessing which patients have [this] cancer and which patients don’t,” said Beth Liles, MD, clinical investigator at the Kaiser Permanente Center for Health Research in Portland (OR, USA) of Kaiser Permanente (Oakland, CA, USA).

“The American Cancer Society and other professional organizations have recommended FIT as a screening tool for CRC since 2008, but there are still many people who don’t know about it,” said Jeffrey Lee, MD, MAS, and postdoctoral researcher at the Kaiser Permanente Division of Research and at the University of California, San Francisco. Unlike older stool tests, FIT does not require people to restrict their diets or to stop taking medications. Conducted annually, FIT detects small amounts of blood in the stool; people who test positive are much more likely to have CRC and so would need a follow-up colonoscopy.

The evidence review found that the FITs were fairly sensitive. On average, the tests detected 79% of CRCs with only one round of testing. The tests were also highly specific: on average, 94% of people who did not have cancer tested negative with a single FIT. By comparison, studies indicate that the at-home fecal occult blood test (FOBT) test, which requires 3 stool samples as well as medication and dietary restrictions, detects only about 13% to 50% of CRCs after a single round of testing.

According to the review, no single FIT performed markedly better than another, but the authors caution that there was only one study comparing brands head-to-head. Most of the FITs required collection of only one stool sample. Surprisingly, brands requiring two or three stool samples were no more accurate than those requiring only one.

The 19 studies included 80 to 27,860 patients, with the average age ranging from 45 to 63. Study settings varied. Eligibility criteria were to include all studies evaluating the diagnostic accuracy of FITs for CRC in asymptomatic, average-risk adults. The review was limited to studies in the English language. Two reviewers independently extracted data and critiqued study quality. In 12 of the studies, all patients took the FIT and received a colonoscopy. In seven studies, patients only had a colonoscopy to follow-up on a positive FIT. Approximately 2 years later, researchers followed up with patients who had had a negative FIT to determine whether they had been diagnosed with CRC.

FITs were concluded to be moderately sensitive, highly specific, and with high overall diagnostic accuracy for detecting CRC. Sensitivity for CRC improved with lower assay cutoff values for a positive test result but with a corresponding decrease in specificity. The study was part of Kaiser Permanente’s ongoing efforts to promote prevention and evidence-based care. Another Kaiser Permanente study also found that patients who visited their doctor for any reason were nearly 6 times more likely to be screened for CRC compared to those who did not visit their doctor.

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