WASHINGTON - The Food and Drug Administration is weighing the benefits and risks of two experimental colon cancer screening tests that use DNA from a patient's stool to detect dangerous tumors and growths.

FDA scientists have questions about the accuracy and the real-world impact of the kits if they are approved. The agency posted its reviews of the tests from Epigenomics and Exact Sciences online, ahead of a two-day meeting that starts Wednesday.

Doctors have long used stool tests to look for hidden blood that can be a warning sign of tumors and precancerous polyps.

Both tests reviewed by the FDA were more accurate at detecting tumors and worrisome growths than the traditional blood stool test. However, both tests also returned more false positives, reporting growths when none were actually present.