Despite guidelines, some patients opt for second fecal blood test following positive result

Although the proportion of patients who repeat tests after receiving a positive result for colorectal cancer is low, at 7.4%, among those that do repeat tests, less than half go on to receive a colonoscopy, according to a study carried out across four large health systems.

Around 7% of patients whose fecal blood test for colorectal cancer (CRC) was positive repeated fecal testing instead of proceeding directly to a colonoscopy, and among those patients, just 41% underwent a colonoscopy within one year of the positive test, results of a mixed methods study show.

Researchers assessed data from 316,443 patients (ages 50 to 89 years) who had a positive fecal blood test between 2010 and 2018. Investigators also carried out interviews with physicians and patients at one of the four large health care systems included in the study. Any patients who had a history of CRC or underwent a colonoscopy within 10 years or flexible sigmoidoscopy within five years before fecal testing were excluded from the study. Current U.S. Preventive Services Task Force guidelines recommend patients with a positive CRC fecal test undergo a colonoscopy, the study authors noted. Findings were published by the Journal of General Internal Medicine on May 21.

Ninety-eight percent of fecal tests were fecal immunochemical tests and 1.9% were guaiac fecal occult blood tests. Just over half of the patients were male and their average age was 61.7 years. Within one year of a positive test, 76.3% of patients received a colonoscopy without repeat fecal testing, 3% repeated testing and then received a colonoscopy, 4.4% repeated testing without colonoscopy, and 16.3% of patients did nothing. Of the 23,312 repeat testers (7.4%), 59% did not receive a colonoscopy within one year. Patients with an initial positive test followed by a negative test were significantly less likely to undergo a colonoscopy than those with repeat positive tests (odds ratio [OR], 0.37; 95% CI, 0.35 to 0.40). Repeat fecal testing was more common with older age (OR for 65–75 years vs. 50–64 years, 1.37; 95% CI, 1.33 to 1.41) and higher Charlson comorbidity score (OR for ≥4 vs. 0, 1.75; 95% CI, 1.67 to 1.83).

The main reasons patients gave for undergoing repeat testing were to avoid a colonoscopy and disbelief of positive results. In interviews, physicians described "struggling to explain why the second test result should not outweigh the first, particularly for those with a mixed results pattern," the authors wrote.

Because the majority of patients included in the study were insured, findings may not be generalizable to other patient populations, the authors cautioned. Overall, "future research is needed on interventions targeting the elimination of repeat fecal testing after a positive test," they concluded.