Signs of Crohn's disease could be present in the blood up to ten years before diagnosis.
This disease causes lasting inflammation of the digestive system. It can lead to stomach pain, diarrhea and severe fatigue. Yet the changes that precede it seem to begin long before doctors make their diagnosis. Researchers set out to find these early traces.
Blood test.
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They analyzed 2,000 blood samples from 500 people. Among them, 200 developed Crohn's disease, another 200 developed a different inflammatory bowel disease, ulcerative colitis, and 100 developed neither of these two diseases. Some samples had been collected ten years before diagnosis.
The researchers focused on antibodies, substances produced by our immune system to recognize what it considers foreign. They can preserve traces of encounters with microbes, but also reveal unusual reactions from our natural defenses.
When comparing the samples, the team noticed that people who would later become ill had different antibody profiles from healthy people.
The researchers then trained a computer program to recognize these profiles. It distinguished fairly well between people who would go on to develop Crohn's disease and those in the control group, even when using older samples. The score obtained, 0.90 on a scale of up to 1, indicates a strong ability to separate the groups studied.
Some profiles also seemed to predict the most difficult-to-treat forms of Crohn's disease. This is an interesting lead: knowing earlier that a person is at risk could help doctors monitor them more closely and, perhaps, intervene before complications appear.
But a blood test cannot yet predict whether someone will develop this disease. The study was presented on October 19 at the UEG Week 2026 medical congress. The results must now be confirmed in other people, in studies that follow them over the years.
The researchers will need to show in particular that their method works outside their original group and provides a real benefit to patients. For now, this discovery mainly shows that the immune system can change silently many years before the first diagnoses.