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The gluten challenge test is a
medical test A medical test is a medical procedure performed to detect, diagnose, or monitor diseases, disease processes, susceptibility, or to determine a course of treatment. Medical tests such as, physical and visual exams, diagnostic imaging, genetic ...
in which
gluten Gluten is a structural protein naturally found in certain Cereal, cereal grains. The term ''gluten'' usually refers to the elastic network of a wheat grain's proteins, gliadin and glutenin primarily, that forms readily with the addition of water ...
-containing foods are consumed and (re-)occurrence of symptoms is observed afterwards to determine whether and how much a person reacts to these foods. The test may be performed in people with suspected
gluten-related disorders Gluten-related disorders is the term for the diseases triggered by gluten, including celiac disease (CD), non-celiac gluten sensitivity (NCGS), gluten ataxia, dermatitis herpetiformis (DH) and wheat allergy. The umbrella category has also been r ...
in very specific occasions and under medical supervision, for example in people who had started a gluten-free diet without performing duodenal biopsy. Gluten challenge is discouraged before the age of 5 years and during
pubertal Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the brain to the gonads: the ovaries in a female, the testicles in a ...
growth. Gluten challenge protocols have significant limitations because a symptomatic relapse generally precedes the onset of a
serological Serology is the scientific study of serum and other body fluids. In practice, the term usually refers to the diagnostic identification of antibodies in the serum. Such antibodies are typically formed in response to an infection (against a given mi ...
and
histological Histology, also known as microscopic anatomy or microanatomy, is the branch of biology that studies the microscopic anatomy of biological tissue (biology), tissues. Histology is the microscopic counterpart to gross anatomy, which looks at large ...
relapse, and therefore becomes unacceptable for most patients.


History

Before serological and biopsy-based diagnosis of coeliac disease was available, a gluten challenge test was a prerequisite for diagnosis of coeliac disease. Today, with serological testing ( determination of coeliac disease-specific antibodies in the blood) and duodenal biopsy with
histological Histology, also known as microscopic anatomy or microanatomy, is the branch of biology that studies the microscopic anatomy of biological tissue (biology), tissues. Histology is the microscopic counterpart to gross anatomy, which looks at large ...
testing being available for diagnosing coeliac disease, patients with suspected coeliac disease are strongly advised to undergo both serological and biopsy testing before undertaking a gluten-free diet. People who present minor damage of the small intestine often have negative blood antibodies titers and many patients with coeliac disease are missed when a duodenal biopsy is not performed. Serologic tests have a high capacity to detect coeliac disease only in patients with total villous atrophy and have very low capacity to detect cases with partial villous atrophy or minor intestinal lesions with normal villi. Currently, gluten challenge is no longer required to confirm the diagnosis in patients with intestinal lesions compatible with coeliac disease and a positive response to a
gluten-free diet A gluten-free diet (GFD) is a nutritional plan that strictly excludes gluten, which is a mixture of prolamin proteins found in wheat (and all of its species and hybrids, such as spelt, kamut, and triticale), as well as barley, rye, and oats ...
. Nevertheless, in some cases, a gluten challenge with a subsequent biopsy may be useful to support the diagnosis, for example in people with a high suspicion for coeliac disease, without a biopsy confirmation, who have negative blood antibodies and are already on a gluten-free diet. Gluten challenge is discouraged before the age of 5 years and during
pubertal Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the brain to the gonads: the ovaries in a female, the testicles in a ...
growth. European guidelines suggest that in children and adolescents with symptoms which are compatible with coeliac disease, the diagnosis can be made without the need for an intestinal biopsy if anti-tTG antibodies titres are very high (10 times the upper limit of normal). A recently proposed criterion to
non-coeliac gluten sensitivity Non-celiac gluten sensitivity (NCGS) or gluten sensitivity is a controversial disorder which can cause both gastrointestinal and other problems. NCGS is included in the spectrum of gluten-related disorders. The definition and diagnostic criteria ...
diagnosis concludes that an improvement of gastrointestinal symptoms and extra-intestinal manifestations higher than 50% with a gluten-free diet, assessed through a rating scale, may confirm the clinical diagnosis of non-coeliac gluten sensitivity. Nevertheless, this rating scale, is not yet applied worldwide. To exclude a
placebo A placebo ( ) can be roughly defined as a sham medical treatment. Common placebos include inert tablets (like sugar pills), inert injections (like saline), sham surgery, and other procedures. Placebos are used in randomized clinical trials ...
effect, a double-blind placebo-controlled gluten challenge is a useful tool, although it is expensive and complicated in routine clinical ground, and therefore, is only performed in research studies.


Testing

The test is also frequently used in
clinical trials Clinical trials are prospective biomedical or behavioral research studies on human subject research, human participants designed to answer specific questions about biomedical or behavioral interventions, including new treatments (such as novel v ...
, for example for assessing the efficacy of novel drugs for patients with coeliac disease. Medical guidelines for performing a gluten challenge vary in terms of the recommended dose and duration of the test.


Preparation

In order to be able to assess the results of the gluten challenge, the patient needs to have been on a
gluten-free diet A gluten-free diet (GFD) is a nutritional plan that strictly excludes gluten, which is a mixture of prolamin proteins found in wheat (and all of its species and hybrids, such as spelt, kamut, and triticale), as well as barley, rye, and oats ...
beforehand, with symptoms having disappeared sufficiently for allowing for a subsequent re-appearance of symptoms under gluten challenge to be observed.


Procedure

It remains unclear what daily intake of gluten is adequate and how long the gluten challenge should last. Some protocols recommend eating a maximum of 10 g of gluten per day for 6 weeks. Nevertheless, recent studies have shown that 2-week challenge of 3 g of gluten per day may induce histological and serological abnormalities in most adults with proven coeliac disease. This newly proposed protocol has shown higher tolerability and compliance, and it has been calculated that its application in secondary-care gastrointestinal practice would identify celiac disease in 7% patients referred for suspected non-coeliac gluten sensitivity, while in the remaining 93% would confirm non-coeliac gluten sensitivity, but is not yet universally adopted. A double-blind placebo-controlled gluten challenge can be performed by means of capsules containing gluten powder (or wheat powder) or a placebo, respectively,Lundin KEA, Alaedini A, ''Non-celiac Gluten Sensitivity''. In: although it is expensive and complicated in routine clinical ground, and therefore, is only performed in research studies. Longer challenges might be necessary in some people especially in adults. There are indications that patients with non-coeliac gluten sensitivity show a reappearance of symptoms in far shorter time than is the case for coeliac disease: in non-coeliac gluten sensitivity, symptoms usually relapse in a few hours or days of gluten challenge. In cases of suspected coeliac disease, a gastrointestinal biopsy is performed at the end of the gluten challenge. For an alternative diagnosis of non-coeliac gluten sensitivity, the reappearance of symptoms is assessed. However, there is no agreement so far as to how to perform a non-coeliac gluten sensitivity symptom evaluation after a gluten challenge. For people eating a
gluten-free diet A gluten-free diet (GFD) is a nutritional plan that strictly excludes gluten, which is a mixture of prolamin proteins found in wheat (and all of its species and hybrids, such as spelt, kamut, and triticale), as well as barley, rye, and oats ...
who are unable to perform an oral gluten challenge, an alternative to identify a possible celiac disease is an
in vitro ''In vitro'' (meaning ''in glass'', or ''in the glass'') Research, studies are performed with Cell (biology), cells or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in ...
gliadin Gliadin (a type of prolamin) is a class of proteins present in wheat and several other cereals within the grass genus ''Triticum''. Gliadins, which are a component of gluten, are essential for giving bread the ability to rise properly during ba ...
challenge of small bowel biopsies, but this test is available only at selected specialized tertiary-care centers.


Variations

For determining whether certain foods such as oats can be tolerated by certain patients, a gradual challenge may be performed.


References

{{Gluten sensitivity Medical tests Challenge test