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Could aspirin enhance performance of stool DNA test for colon cancer?

Reuters Health • The Doctor's Channel Daily Newscast

NEW YORK (Reuters Health) – There’s no need for people to stop taking aspirin before an immunochemical fecal occult blood test (iFOBT) because it won’t hamper the performance of the test, a new study suggests. On the contrary, low-dose aspirin therapy might actually boost the test’s performance.

Stool DNA tests have been gaining attention as a cost-effective and less invasive alternative to colonoscopy for colorectal cancer screening. Because the target population for these tests is likely to be on low-dose aspirin, there have been suggestions that aspirin should be stopped prior to FOBTs.

But this appears to be unnecessary, Dr. Hermann Brenner of the German Cancer Research Center in Heidelberg and colleagues say. They assessed the performance of two quantitative iFOBTs (hemoglobin test and hemoglobin-haptoglobin test) both in the presence and absence of low-dose aspirin.

Among 1,979 study patients with an average age of 62 years, 233 were regular users of low-dose aspirin and 1,746 never used low-dose aspirin.

In the online December 7 Journal of the American Medical Association, they report that, for both tests, sensitivity for detecting advanced colorectal neoplasms was markedly higher in aspirin users than nonusers, while specificity was only slightly lower in aspirin users.

“Some increase in both the true positive rate (sensitivity) and the false positive rate among users of low-dose aspirin was expected,” Dr. Brenner told Reuters Health.

“The good, and to some extent, surprising news was that the increase in the true positive rate was so much larger than the increase in the false positive rate, so that test performance was, overall, much better among users of low-dose aspirin,” he added.

Specifically, advanced neoplasms were found in 24 users (10.3%) and 181 nonusers (10.4%) of low-dose aspirin.

The sensitivity with the hemoglobin test was 70.8% in aspirin users compared with 35.9% in nonusers; specificity was 85.7% in users compared with 89.2% in nonusers.

For the hemoglobin-haptoglobin test, sensitivity was 58.3% in aspirin users compared with 32.0% in non-users and specificity was 85.7% and 91.1%, respectively.

For the iFOBTs assessed in this study at least, “there is no need to stop low-dose aspirin,” Dr. Brenner said. “On the contrary, simultaneous application of low-dose aspirin might even enhance test performance.” This, he said, is something that should be studied.