Blood tests get cold-shouldered
Liquid biopsies. Blood draws. The promise of painless screening for colorectal cancer has been the darling of the industry lately. The American Cancer Society just pulled the rug out.
In its major guideline update— the first since 2018 — the ACS says blood-based tests are not a preferred option.
Not even close.
They’re allowed only as a last resort for people who absolutely refuse stool tests or colonoscopies. Why? Because they miss too much. The main point of screening isn’t just to find cancer. It is to prevent it by hunting down precancerous polyps before they mutate.
Blood tests have abysmal sensitivity for those pre-cancerous lesions. We’re talking roughly 13%. That’s it. Two large studies confirmed this gap. If the test misses the polyp, it can’t remove the cancer threat. That defeats the purpose.
Older adults have another headache. Specificity drops with age. For people over 70, the chance of a false positive rises sharply. That means more unnecessary colonoscopies with their own risks, driven by test errors rather than real disease.
A blood test is better than nothing? Sure. If you won’t do anything else. But it is not the gold standard. Not anymore.
Two stool tests make the cut
The real news is in the stool. Two new FDA-approved options are now preferred :
- ColoSense (mt-sRNA)
- Cologuard Plus (ng-mt-sDNA)
Both launched in 2024 after showing they can spot cancer and significant precancers with high accuracy. ColoSense uses RNA markers alongside a blood check and smoking history. It caught stage I cancers 100% of the time in validation studies.
Cologuard Plus tweaks the original formula for better precision without sacrificing sensitivity.
Both are done every three years. They sit alongside the trusted annual stool blood tests (FIT) and older DNA tests.
The math checks out. Modeling suggests all these options reduce deaths and cases similarly. The catch? Access. Medicare and Medicaid coverage for the shiny new ColoSense is still in limbo. That leaves a gap for patients who need these options but can’t afford them out-of-pocket.
A positive screening result is the beginning of the diagnosis, not the end.
Positive means scope
Here is a rule you cannot negotiate.
Get a positive stool test? You need a colonoscopy.
Ideally within six months. The guidelines are blunt: you cannot repeat the stool test. You cannot switch to a blood test to verify. You have to go under.
People ignore this step all the time. Self-reported data is full of holes because folks stop once they get their result slip in the mail. A trial showed only 50% of people with positive blood tests followed through with scopes within half a year. Even fewer finished the journey when compared to stool test positives.
Why? Fear. Hassle. Procrastination.
Does it matter? Yes. Without the colonoscopy to remove the growth, the screening was for naught.
45 is the new normal
Start at 45. That recommendation from 2018 stays.
Cancer is creeping earlier. Incidence in adults under 50 rose by 3% every year from 2013 to colorectal cancer is now the top cause of cancer death in young men. Second in women. Diet seems to play a heavy role, particularly for women in this age bracket.
But the numbers look bleak for uptake.
Only 37% of people aged 45-49 were up-to-date with screening in 2023. Disparities are stark. Hispanic, Asian, and Indigenous adults trailed behind White and Black peers in getting screened.
Why the lag? It isn’t just fear of the scope.
Black Americans face CRC rates 11% higher and mortality 40% higher than Whites. Alaska Natives have more than double the incidence. Indigenous populations overall see rates nearly 50% higher.
Money blocks access. Insurance status matters. And while older tests remain cheaper, the cost of these new molecular stool tests will be a wall for the underinsured. The ACS notes that simply having more choices doesn’t help if those choices are expensive or out of reach. Equity requires coverage. Period.
The goal remains: stop the disease before it starts. Lifestyle helps too. Alcohol intake matters. But none of that replaces the scope.
So. What is the best test?
The one you actually do.
Talk to a doctor. Don’t guess. Because waiting doesn’t make the cancer go away. It only makes it louder.
