Could Crohn’s disease leave a trail in your blood long before the first cramp or urgent bathroom trip? A study presented on October 19, 2026, at UEG Week in Barcelona, Europe’s largest gastroenterology meeting, suggests it can. By testing blood samples that had been stored for years, an international team found antibody patterns linked to inflammatory bowel disease (IBD) up to 10 years before diagnosis. It is a research finding, not a test you can order yet. Here is what the study showed, and what a routine Crohn’s disease blood test can and cannot tell you today.
What the UEG Week 2026 study found
The work was led by Dr. Arno Bourgonje, of University Medical Center Groningen in the Netherlands, who carried it out during a fellowship at the Icahn School of Medicine at Mount Sinai in New York. The team used a U.S. military serum bank, where blood drawn during routine service is stored for years. They analyzed 2,000 samples from 500 people: 200 who later developed Crohn’s disease, 200 who later developed ulcerative colitis, and 100 matched people who stayed healthy. Each person had four samples, taken at diagnosis and roughly two, four and 10 years earlier.
Every sample was screened against about 357,000 fragments of bacteria, viruses, foods and human proteins. People heading toward IBD had a narrower range of antibodies than the healthy group, and clear differences were already visible a decade out.
- In future Crohn’s disease, antibodies against herpes-family viruses (including Epstein-Barr virus) and against flagellin, the protein that lets some gut bacteria swim, were higher, especially in people who later had complicated disease or disease of the ileum.
- Responses to certain “encapsulated” bacteria, such as pneumococcus, faded steadily as diagnosis approached.
- Future ulcerative colitis showed rising antibodies against herpes viruses and against the body’s own proteins (autoantibodies).
According to the congress press release, computer models separated future Crohn’s cases from healthy people with a score of 0.90 and predicted complicated Crohn’s with a score of 0.85, on a scale where 1.0 is perfect and 0.5 is a coin flip. The authors call it a proof of principle: the signatures still have to be confirmed in other, more diverse groups followed over time, and turned into an affordable lab test, before anyone could use them in practice. The descriptive part of the work was published in July 2026 in the journal Gut.
Latest scientific advances: Crohn’s starts before symptoms do
This study joins a run of recent research pointing in the same direction: Crohn’s disease has a silent “preclinical” phase. A 2023 review in Nature Reviews Gastroenterology & Hepatology describes it as a series of stages, from inherited risk to inflammation that builds quietly before anyone feels it.
Several possible blood signatures are emerging:
- Blood proteins. A Swedish-led team reported in 2024 in Gastroenterology that a set of proteins, many tied to the gut lining’s barrier function, could flag people who would later develop Crohn’s. A 2025 analysis of the UK Biobank in Nature Communications picked up a protein signal as long as 16 years before diagnosis.
- Antibodies to gut bacteria. In healthy parents, siblings and children of people with Crohn’s, a Canadian study published in 2026 linked an immune reaction to one shared piece of bacterial flagellin with a higher chance of developing the disease.
- The shape of antibodies. A 2024 study in Nature Immunology found that antibodies in future patients carry different sugar chains, which makes them more inflammatory, and tied this to anti-yeast antibodies (ASCA) that doctors already know.
- Stool calprotectin. Among relatives with no symptoms, a 2026 study in Gut showed that persistently high fecal calprotectin helped find early Crohn’s lesions on bowel exams.
What this means for you: nothing changes in your care right now. These tools are being used to pick volunteers for prevention trials, such as diet studies in relatives of patients. The long-term goal is to spot people at risk early enough to slow down, or even prevent, the disease.
What a Crohn’s disease blood test can show today
No single blood test confirms or rules out Crohn’s disease. The diagnosis is built from symptoms, a physical exam, blood and stool tests, and a look inside the bowel with colonoscopy and biopsies or imaging. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) notes that blood tests look for anemia, signs of infection or inflammation such as a high white cell count, and raised C-reactive protein. For the basics of the condition, see our complete guide to Crohn’s disease.
If you already have results in hand, three habits help: read blood and stool results together, watch the trend over time rather than one number, and do not draw conclusions from a single flagged value on your own.
Which tests can monitor or screen for this?
| Test | What it measures | What it can suggest |
|---|---|---|
| Complete blood count (CBC) | Red cells, white cells, platelets | Anemia from bleeding or poor absorption; high platelets or white cells with inflammation |
| C-reactive protein (CRP) | Body-wide inflammation | An active flare, though it can stay normal in some people |
| Ferritin, vitamin B12, albumin | Iron stores, absorption, nutrition | Deficiencies that are common when the ileum is involved or inflammation lasts |
| Fecal calprotectin | Inflammation in the bowel wall | Bowel inflammation rather than irritable bowel syndrome; useful for follow-up |
| ASCA and ANCA antibodies | Antibodies to a yeast or to certain white cells | A hint toward Crohn’s or ulcerative colitis in unclear cases; never a diagnosis on their own |
Learn more: CRP as an inflammation marker, how to read a complete blood count, low ferritin and fecal calprotectin results.
When to see a doctor
Talk to your primary care provider if you have had diarrhea that will not settle, repeated belly pain, unexplained weight loss, lasting fatigue or sores and abscesses around the anus for several weeks, especially if a close relative has IBD. An abnormal lab result without symptoms is also worth discussing, calmly. Seek emergency care or call 911 for severe abdominal pain, high fever, repeated vomiting or heavy bleeding from the rectum.
Glossary
- Inflammatory bowel disease (IBD): a group of long-term gut conditions that includes Crohn’s disease and ulcerative colitis.
- Preclinical phase: the period when a disease is developing in the body but causes no symptoms yet.
- Antibodies: proteins the immune system makes to recognize a germ or another substance.
- Flagellin: the protein that forms the whip-like tail some bacteria use to move.
- Ileum: the last part of the small intestine, often affected in Crohn’s disease.
- Fecal calprotectin: a protein measured in stool that reflects inflammation in the bowel.
Frequently asked questions
Can I get a blood test now to find out if I will develop Crohn’s disease?
No. The antibody and protein signatures in these studies are research tools. No lab offers a routine test that predicts Crohn’s disease.
Does a normal blood test rule out Crohn’s disease?
Not always. CRP and the CBC can be normal even when the bowel is inflamed. Fecal calprotectin and a look inside the bowel complete the picture.
My parent has Crohn’s. Should I be screened?
There is no routine screening for relatives. Your risk is higher than average, but most relatives never develop the disease. Mention your family history to your doctor if you have gut symptoms.
Are ASCA antibodies enough to diagnose Crohn’s?
No. They can point in a direction in some cases, but they are not reliable enough to confirm or exclude the disease on their own.
Why does Epstein-Barr virus show up in this study?
Future patients reacted more strongly to this very common virus. That suggests an immune system already out of balance, but it does not prove the virus causes Crohn’s.
Sources
- Bourgonje AR et al. Deciphering the prodrome of inflammatory bowel disease up to 10 years before disease onset by massively parallel serology. Gut, 2026. DOI: 10.1136/gutjnl-2025-337762
- United European Gastroenterology. UEG Week 2026 press release (Barcelona, October 19, 2026), via ScienceDaily
- Rudbaek JJ et al. Deciphering the different phases of preclinical inflammatory bowel disease. Nature Reviews Gastroenterology & Hepatology, 2023. DOI: 10.1038/s41575-023-00854-4
- Grännö O et al. Preclinical protein signatures of Crohn’s disease and ulcerative colitis. Gastroenterology, 2024. DOI: 10.1053/j.gastro.2024.11.006
- Feng et al. Plasma proteomic profiles identify biomarkers predicting Crohn’s disease up to 16 years before onset. Nature Communications, 2025. DOI: 10.1038/s41467-025-66483-4
- Wu RY et al. Serum IgG response to a conserved domain of commensal flagellins predicts future risk of Crohn’s disease in first-degree relatives. Clinical Gastroenterology and Hepatology, 2026. DOI: 10.1016/j.cgh.2025.12.006
- Gaifem J et al. A unique serum IgG glycosylation signature predicts development of Crohn’s disease. Nature Immunology, 2024. DOI: 10.1038/s41590-024-01916-8
- Turner D et al. Preclinical stages of Crohn’s disease defined by faecal calprotectin in asymptomatic first-degree relatives. Gut, 2026. DOI: 10.1136/gutjnl-2025-336368
- NIDDK. Diagnosis of Crohn’s disease
Further reading
- IBD remission: why flares come back when your tests look fine
- Ulcerative colitis blood test: what your results really show
- Irritable Bowel Syndrome: Symptoms, Tests, and Treatment
- EBV Reactivation After COVID: What Your Blood Test Results Mean
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