After the ACS update, when does a blood test fit colorectal screening?

The American Cancer Society’s May 27, 2026 update did not make a blood test interchangeable with colonoscopy. For average-risk adults, the society still says colorectal cancer screening should start at age 45 and continue through age 75 for people with a life expectancy greater than 10 years. Adults ages 76 to 85 should make an individualized decision with a clinician, and screening is not recommended after 85. Stool-based tests and visual exams remain the preferred choices. Blood-based tests were added as recommended, but non-preferred, options. ([pressroom.cancer.org](https://pressroom.cancer.org/colorectal-cancer-screening-guideline-update-2026))

That new option is mainly meant for people who decline or do not complete preferred screening tests. ACS also says people should still be offered a choice between stool testing and a direct visual exam, and it continues to stress that the most effective test is the one a patient actually completes on time. ([pressroom.cancer.org](https://pressroom.cancer.org/colorectal-cancer-screening-guideline-update-2026))

Why a blood test may be easier, but not equivalent

The main appeal is simplicity: a blood draw in a clinic may feel easier than bowel prep for colonoscopy or completing a stool test at home. But the tradeoff is what the test can miss. In the ECLIPSE study, a prospective, multicenter accuracy study published in The New England Journal of Medicine and funded by Guardant Health, the blood test detected 87.5% of stage I to III colorectal cancers overall, but 65% of stage I cancers and 13.2% of advanced precancerous lesions. That matters because advanced precancerous lesions are one of the main targets of screening before they turn into cancer. ([nejm.org](https://www.nejm.org/doi/full/10.1056/NEJMoa2304714?utm_source=openai))

That evidence helps explain why ACS left blood testing in a lower tier. The group says blood-based tests are less sensitive than established stool-based tests for advanced precancerous lesions and stage I cancers, with studies predicting less effectiveness in reducing colorectal cancer incidence and mortality. Colonoscopy also has an advantage a blood test does not: if a suspicious polyp is found, it can often be removed during the same procedure. ([pressroom.cancer.org](https://pressroom.cancer.org/colorectal-cancer-screening-guideline-update-2026))

A positive blood test still means colonoscopy

The follow-up rule is one of the most important practical details. ACS says any positive stool or blood-based screening test should be followed by colonoscopy, preferably within 6 months, to complete screening. FDA’s approval page for Shield says people with positive results are advised to have diagnostic colonoscopy, and that a negative result does not guarantee a person does not have colorectal cancer. ([pressroom.cancer.org](https://pressroom.cancer.org/colorectal-cancer-screening-guideline-update-2026))

Who this option may fit — and who it does not

FDA says Shield is for adults 45 and older who are at average risk and need colorectal cancer screening. It is not a replacement for diagnostic colonoscopy or surveillance colonoscopy in people at higher risk. Medicare’s coverage page uses a similar definition: ages 45 to 85, no symptoms of colorectal disease, and no personal history or family history that places someone in a higher-risk group. ([fda.gov](https://www.fda.gov/medical-devices/recently-approved-devices/shield-p230009))

That means this is a screening option for people without symptoms. If you have blood in the stool or lower gastrointestinal pain, or you have a personal history of colorectal cancer, adenomas, inflammatory bowel disease, or an inherited high-risk syndrome, this is not a substitute for medical evaluation. In those situations, a reasonable next step is prompt medical care rather than routine screening. ([medicare.gov](https://www.medicare.gov/coverage/blood-based-biomarker-tests-for-colorectal-cancer-screening))

Coverage and follow-up planning matter

Medicare Part B covers blood-based biomarker screening once every 3 years for eligible beneficiaries ages 45 to 85 who are at average risk and have no symptoms. Medicare also says a follow-up colonoscopy after a positive blood test is covered as a screening test, and people pay nothing for the blood test if the provider accepts assignment. That is useful for Medicare patients, but it does not settle every cost question for people outside Medicare, so checking plan details and follow-up logistics before testing is still wise. ACS’s advocacy arm said coverage and affordability remain major barriers to screening. ([medicare.gov](https://www.medicare.gov/coverage/blood-based-biomarker-tests-for-colorectal-cancer-screening))

Why an easier option could still help

A simpler test may still matter because too many eligible adults remain unscreened. A CDC analysis of 2022 BRFSS data found that 61.4% of U.S. adults ages 45 to 75 were up to date with colorectal cancer screening. Among adults ages 45 to 49, only 29.8% were up to date and 65.7% had never been screened. Those numbers are self-reported, and the survey’s overall response rate was 45.1%, so they are useful context rather than a perfect measure. ([cdc.gov](https://www.cdc.gov/pcd/issues/2025/25_0175.htm))

Bottom line

After the ACS update, a blood test makes the most sense when an average-risk adult age 45 or older is not going to complete a preferred screening option and needs a more acceptable starting point. It is better understood as an alternative to staying unscreened, not as a one-step replacement for colonoscopy. A practical next step is to ask a clinician whether you are average risk, which screening test you are most likely to complete on time, and how follow-up colonoscopy would be arranged if the result is positive. ([pressroom.cancer.org](https://pressroom.cancer.org/colorectal-cancer-screening-guideline-update-2026))

Sources

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This article is for general informational purposes only and is not medical advice. Research findings can be early or incomplete, and health guidance can change. Always talk with a qualified healthcare professional about personal symptoms, diagnosis, medications, vaccines, screenings, or treatment decisions. If you think you may have a medical emergency, call emergency services right away.