FDA Approves a New Blood Test for Colorectal Cancer Screening

The FDA has approved a new blood-based test for colorectal cancer screening — the kind of simple blood draw that could pull more people into getting checked.

Approved on July 27, 2026, Freenome’s SimpleScreen CRC test (to be commercialised in the US by Abbott) is intended for adults 45 and older at average risk. It joins Guardant Health’s earlier Shield test in a fast-growing category.

How well it works

SimpleScreen detected colorectal cancer with 81.1% sensitivity and had 90.4% specificity for advanced disease. The important weakness: it caught only 13.7% of advanced precancerous lesions — the polyps colonoscopy can find and remove before they become cancer.

Why the polyp number is the one that matters

Colorectal cancer screening is unusual among cancer screening programmes because it can prevent the disease rather than only detect it.

Most colorectal cancers develop from adenomatous polyps over a period of years. Removing a polyp during colonoscopy means the cancer that would have developed from it never does — so the procedure is therapeutic as well as diagnostic.

That is why colonoscopy screening reduces colorectal cancer incidence, not merely mortality. Screening programmes for most other cancers can only find disease earlier.

A test detecting 13.7% of advanced precancerous lesions misses roughly six in seven opportunities to prevent a cancer. It is a cancer-detection test, and the prevention function is largely absent.

What the biology explains

The performance gap follows from what these tests measure.

Blood-based tests detect material shed by a tumour into the circulation — typically fragments of tumour DNA, sometimes proteins or other markers. Shedding depends on the lesion having a blood supply and enough cellular turnover to release detectable quantities.

An established cancer meets those conditions. A precancerous polyp is small, has limited vasculature and sheds far less, so there is often nothing detectable in a tube of blood.

That is a physical constraint rather than a limitation of the current generation, which is why the gap is likely to persist.

Why it matters anyway

Roughly a third of eligible Americans are not up to date on colorectal screening, often because stool tests and colonoscopy prep are off-putting.

The barriers are concrete. Colonoscopy requires a day of bowel preparation involving large volumes of laxative, a day off work, sedation and usually someone to accompany the patient home. Stool tests require handling a sample at home, which many people decline.

A blood test requires none of that, and easier tests get done. Comparing an imperfect test that is completed against a superior one that is refused is a different calculation from comparing the tests directly.

The caveat

Regulators and doctors are clear: these blood tests are not a replacement for colonoscopy, especially given the low detection of precancerous polyps.

They are best seen as a bridge for people who would otherwise skip screening entirely.

The risk is that they are not used that way. A person who would have had a colonoscopy but chooses the blood test instead has substituted a less effective option, and a normal result may be read as reassurance that removes the impetus to do anything more thorough.

What happens after a positive result

A blood test is not the end of the pathway, and understanding what follows clarifies what these tests actually change.

Any positive result requires colonoscopy to identify what produced it. The blood test indicates something may be present; it does not locate it, characterise it, or remove it. So a person with a positive result faces the procedure they may have been avoiding, now with the anxiety of an abnormal finding.

Specificity determines how often that happens unnecessarily. At around 90%, roughly one in ten people without advanced disease will be told their result is abnormal — and because the great majority of screened people do not have cancer, false positives substantially outnumber true ones in absolute terms.

Colonoscopy capacity is the system-level consequence. Screening programmes that generate more referrals than endoscopy services can absorb create waiting lists, and the people waiting include those with genuine disease.

None of that argues against the test. It does mean the benefit depends on the pathway behind it functioning — an easier front door is only useful if the room behind it has space.

Why screening starts at 45

The eligibility age in the approval reflects a change made in recent years, and the reason behind it is worth noting.

Guidelines long recommended beginning colorectal screening at 50. That threshold was lowered to 45 after data showed rising incidence among younger adults — a trend observed across several countries and not explained by increased detection alone.

The causes remain unsettled. Proposed contributors include obesity, dietary patterns, sedentary behaviour and changes in the gut microbiome, none of which has been established as the driver. What is clear is that people born more recently carry higher risk at any given age than earlier cohorts did.

Lowering the age expanded the eligible population substantially, which sharpened the capacity problem: more people to screen, with the same endoscopy resources. That context is part of why easier screening options attract interest, and part of why the trade-off between accessibility and effectiveness is being weighed as actively as it is.

Whether the category improves outcomes depends on which patients take it up — those who were screening already, or those who were not. General information, not medical advice.