Non-celiac gluten sensitivity (NCGS) refers to the subset of persons who report improvement in GI symptoms when they discontinue gluten-containing foods.
This process contrasts with celiac disease (CD), an autoimmune disease that causes inflammation and tissue damage in the small intestine, which can be diagnosed by upper endoscopic biopsy.
Many studies suggest that the irritable bowel syndrome (IBS) has patients with undiagnosed celiac disease.
It is suspected that a significant fraction of IBS patients in whom CD has been ruled out may have NCGS.
Note that serologies for celiac disease and biopsy can be falsely normal if the patient is on a gluten-free diet.
Adults always need a biopsy to confirm suggestive serologies for celiac disease.
Only about 17% of the 1.8 million-person US celiac population actually has a diagnosis and is on a gluten-free diet.
A similar number, 1.6 million, are currently on a gluten-free diet without a diagnosis of CD.
Studies suggesting genetic similarities and symptom resolution with gluten cessation in symptomatic individuals, despite negative duodenal biopsies while consuming gluten.
Some studies have shown biopsy-negative persons with serologic markers for CD have symptom resolution when off gluten, diarrhea in particular.