Examinations for Celiac Disease Diagnosis

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Generality

The examinations used for the diagnosis of celiac disease essentially include the patient's medical history and objective observation, the search for specific antibodies and autoantibodies in his blood, the execution of the sorbitol breath test, the stool test, and, in last analysis, the gold standard exam: duodenal biopsy.

Exam preparation

Before undergoing these tests it is important that the patient maintains their dietary habits, unless otherwise prescribed by a doctor. If, for example, the subject stops taking gluten-containing foods, he could be falsely negative to the tests used for the diagnosis of celiac disease, thus appearing healthy despite the disease.

Anamnesis and physical examination

In this preliminary phase the doctor tries to highlight the symptoms, or the sensations reported by the patient about his own health condition, and the clinical signs (objective symptoms detected by the same doctor) typical of celiac disease. These symptoms are essentially gastrointestinal in origin and include dyspepsia, diarrhea or constipation, malaise, flatulence and abdominal distention; in an advanced stage these symptoms, typical of malabsorption syndromes, are combined with those of malnutrition: short stature in children, pubertal delay, weight loss, iron deficiency anemia and folate deficiency, vitamin deficiency, osteoporosis and osteomalacia. It should be remembered, however, that the clinical spectrum of this pathology is extremely varied and heterogeneous, also as regards the intensity of the symptoms, which can be severe or extremely nuanced.

Search for specific autoantibodies

The extreme variability of the clinical picture of celiac disease, and its similarity to that typical of other diseases (syndrome of bacterial contamination of the small intestine, Crohn's disease, irritable bowel syndrome and pancreatic insufficiency) requires that, in the face of clinical suspicion, they are performed further assessment tests.

Among the first-line tests we recall the blood dosing of particular antibodies and autoantibodies, such as anti-tissue transglutaminase (tTGA, the most used for diagnostic purposes), anti-endomysium antibodies (EMA, directed against the components of intestinal cells of the 'organism) and antigliadin antibodies (AGA, aimed at gluten components and less clinically important due to the high rate of false positives).

If the levels of these antibodies appear above normal, the patient is probably celiac and therefore eligible for further assessment tests. Patients with high anti-tissue transglutaminase antibody titers and anti-endomysium antibodies have a 95% chance of being celiac.

At the moment, the validation of the use of other antibodies in the diagnosis of celiac disease, such as the antireticolin antibodies R1 (R1-ARA) and the antidigiunals (JAB) is in progress.

Sorbitol Breath Test

This diagnostic test is particularly useful in celiac disease screening; it is performed by administering 5 grams of sorbitol to the patient and then measuring the concentration of hydrogen in the expired air at regular intervals. If this increases it means that sorbitol has escaped absorption in the small intestine and has been fermented by the bacterial flora of the colon, producing intestinal gases including hydrogen.

A sorbitol breath test positivity therefore indicates a problem of intestinal malabsorption, common among celiac subjects but also to other diseases, for example in case of pancreatic insufficiency, small bacterial contamination syndrome, short bowel syndrome and Crohn's disease .

Stool examination

Stool examination is poorly used for the diagnosis of celiac disease, although it may be useful to identify patients to be subjected to further investigations (screening method). In the presence of malabsorption syndromes it is possible to find an excessive quantity of fats in the fecal sample (steatorrhea) and an acid pH of the faeces. Similar to the sorbitol breath test, the positive test is recorded in the presence of any generic cause of intestinal malabsorption.

Duodenal biopsy

This is the gold standard for the diagnosis of celiac disease, that is, the examination that leaves less room for methodological errors and interpretation of results. This is an invasive test, performed on subjects positive to previous tests to obtain diagnostic confirmation of celiac disease.

The examination is carried out by esophagogastroduodenoscopy, during which a long and thin flexible tube is inserted through the oral cavity and made to flow down the esophagus up to the stomach and the first part of the intestine. This instrument is equipped with a camera with a light source and micro-surgical instruments can be slid through the tube to withdraw small samples of the intestinal mucosa, subsequently observed in the laboratory.

Since the celiac disease subverts the normal architecture of the intestinal mucosa, with the flattening of the villi, the cytological examination allows us to confirm or exclude celiac disease with almost absolute certainty. The exam loses diagnostic value in the presence of allergies to milk or soy proteins, however rare and mostly childhood-like diseases that are accompanied by overlapping histological findings; analogous speech in the presence of viral gastroenteritis that can however be recognized a priori for the sudden appearance of symptoms, for their severity and for their trend over time.