American Cancer Society Adds Blood Test to Colorectal Screening Options

Originally surfaced May 21, 2026.

In May 2026 the American Cancer Society updated its colorectal cancer screening guidelines to include Guardant Health's Shield blood test as a primary screening option for average-risk adults aged 45 and older. Shield is FDA approved, detects circulating tumor DNA, and is specifically positioned for people who have declined or have not completed stool-based or colonoscopy-based screening.

This is a real expansion. It is also a guideline change that needs to be read carefully, because it does not mean that a blood test is now equivalent to a colonoscopy for colorectal cancer screening.

What changed

The ACS update lists Shield alongside the existing screening options for average-risk adults 45 and older. The pitch is straightforward: a single venous blood draw, no bowel prep, no scope, no stool collection. For a meaningful share of eligible adults who simply have not gotten screened by any other method, that lowers the practical activation cost of doing something.

The Shield test is FDA approved and has been studied in the ECLIPSE trial. The ACS frames it as particularly useful for patients who decline or have not completed traditional screening methods.

What the test is good at and what it is not

Shield is a screening tool for colorectal cancer, not for advanced precancerous polyps. Sensitivity for advanced precancerous lesions and for early-stage cancer is meaningfully lower than colonoscopy. Colonoscopy is still the most thorough single test because it can find and remove polyps in the same visit, which prevents cancer rather than detects it.

Stool-based tests, including FIT and multi-target stool DNA, sit somewhere in between. They are more sensitive than Shield for some endpoints, less convenient than a blood draw, and more convenient than a colonoscopy.

The right way to read the ACS change is not that the blood test wins. It is that no screening is worse than imperfect screening, and the blood test is real screening for the right person.

The relevant testing context

The Shield test itself is a clinician-ordered, often insurance-billed test. It is not a self-pay direct-to-consumer panel and LabTestSuperstore does not offer it.

What LabTestSuperstore can offer is context. CEA, or carcinoembryonic antigen, is a tumor marker used in patients with known colorectal cancer to monitor treatment and recurrence. It is not a screening tool for average-risk adults and ACS does not endorse it for screening. The comprehensive health profile covers general baseline labs that are useful context for an overall health conversation, including the conversation with a clinician about which colorectal screening modality fits.

This article is editorial commentary and is not medical advice. Colorectal cancer screening decisions, including which modality and how often, should be made with a clinician who knows your personal and family history.