Celiac disease is an autoimmune disorder suffered by genetically predisposed individuals. Upon exposure to gluten, a protein found in wheat, the bodies of these individuals initiate an autoimmune response targeted at their intestinal lining. This leads to inflammation and damage to the intestines, resulting in diarrhea, constipation, and improper absorption of nutrients and vitamins.
Diagnosis of celiac disease can be complicated, often involving blood tests and endoscopic biopsy (accomplished by sedating the patient, passing a tube into the gastrointestinal system through the mouth, and removing a tiny section of the intestinal wall for microscopic evaluation).
A separate condition called non-celiac gluten sensitivity causes many of the same symptoms as celiac disease. Celiac disease can be ruled out through diagnostic testing in these individuals; however, the treatment for non-celiac gluten sensitivity is practically identical to the treatment for celiac disease - strict adherence to a gluten-free diet. Despite this, differentiating between the two conditions is important, as the intestinal damage and autoimmune features of the more serious celiac disease can have severe health implications.
Research actually showed that patients with negative celiac blood tests while on a normal, gluten-containing diet were unlikely to have celiac disease. These individuals were also very unlikely to exhibit signs of malabsorption (such as weight loss and nutrient deficiencies), and usually did not have personal histories of autoimmune conditions or family histories of celiac disease. This means that in patients with all of these characteristics, celiac disease can usually be ruled out without the need for biopsy, and that these patients likely suffer from the less serious non-celiac gluten sensitivity.