Endomysial antibodies

(redirected from gliadin deamidated peptide antibodies)

Antibodies, Gliadin (Immunoglobulin G and Immunoglobulin A), Endomysial (Immunoglobulin A), Tissue Transglutaminase (Immunoglobulin A)

Synonym/acronym: Endomysial antibodies (EMA), gliadin deamidated peptide (IgG and IgA) antibodies, tTG.

Common use

To assist in the diagnosis and monitoring of gluten-sensitive enteropathies that may damage intestinal mucosa.

Specimen

Serum (1 mL) collected in a red-top tube.

Normal findings

(Method: Enzyme linked immunosorbent assay [ELISA] for gliadin antibody and tissue transglutaminase antibody; indirect immunofluorescence for endomysial antibodies)
Conventional Units
IgA and IgG Gliadin AntibodyLess than 20 units
Tissue transglutaminase antibodyLess than 20 units
Endomysial antibodiesNegative

Description

Gliadin is a water-soluble protein found in the gluten of wheat, rye, oats, and barley. The intestinal mucosa of certain individuals does not digest gluten, allowing a toxic buildup of gliadin and intestinal inflammation. The inflammatory response interferes with intestinal absorption of nutrients and damages the intestinal mucosa. In severe cases, intestinal mucosa can be lost. Immunoglobulin G (IgG) and immunoglobulin A (IgA) gliadin antibodies are detectable in the serum of patients with gluten-sensitive enteropathy. Endomysial antibodies and tissue transglutaminase (tTG) antibody are two other serological tests commonly used to investigate gluten-sensitive enteropathies. Gliadin IgA tests are the most sensitive for celiac disease (CD). However, it is also recognized that a significant percentage of patients with CD are also IgA deficient, meaning false-negative IgA results may be misleading in some cases. Estimates of up to 98% of individuals susceptible to CD carry either the DQ2 or DQ8 HLA cell surface receptors, which initiate formation of antibodies to gliadin. While it appears there is a strong association between CD and these gene markers, up to 40% of individuals without CD also carry the DQ2 or DQ8 markers. Molecular testing is available to establish the absence or presence of these susceptibility markers. CD is an inherited condition with significant impact on quality of life for the affected individual. The use of serological markers is useful in disease monitoring because research has established a relationship between amount of gluten in the diet and degree of intestinal damage as reflected by the level of detectable antibodies. CD shares an association with a number of other conditions such as type 1 diabetes, Down’s syndrome, and Turner’s syndrome.

This procedure is contraindicated for

    N/A

Indications

  • Assist in the diagnosis of asymptomatic gluten-sensitive enteropathy in some patients with dermatitis herpetiformis
  • Assist in the diagnosis of gluten-sensitive enteropathies
  • Assist in the diagnosis of nontropical sprue
  • Monitor dietary compliance of patients with gluten-sensitive enteropathies

Potential diagnosis

Increased in

  • Evidenced by the combination of detectable gliadin or endomysial antibodies and improvement with a gluten-free diet.

  • Asymptomatic gluten-sensitive enteropathy
  • Celiac disease
  • Dermatitis herpetiformis (etiology of this skin manifestation is unknown, but there is an association related to gluten-sensitive enteropathy)
  • Nontropical sprue

Decreased in

    IgA deficiency (related to an inability to produce IgA and evidenced by decreased IgA levels and false-negative IgA gliadin tests) Children under the age of 18 mo (related to immature immune system and low production of IgA)

Critical findings

    N/A

Interfering factors

  • Conditions other than gluten-sensitive enteropathy can result in elevated antibody levels without corresponding histological evidence. These conditions include Crohn’s disease, postinfection malabsorption, and food protein intolerance.
  • A negative IgA gliadin result, especially with a positive IgG gliadin result in an untreated patient, does not rule out active gluten-sensitive enteropathy.

Nursing Implications and Procedure

Pretest

  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching: Inform the patient this test can assist with evaluating the ability to digest gluten foods such as wheat, rye, and oats.
  • Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
  • Obtain a history of the patient’s gastrointestinal and immune systems, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Obtain a list of foods and the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
  • Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction.

Intratest

  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
  • Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
  • Promptly transport the specimen to the laboratory for processing and analysis.

Post-Test

  • Inform the patient that a report of the results will be made available to the requesting health-care provider (HCP), who will discuss the results with the patient.
  • Nutritional Considerations: Encourage the patient with abnormal findings to consult with a qualified nutritionist to plan a gluten-free diet. This dietary planning is complex because patients are often malnourished and have other related nutritional problems.
  • Recognize anxiety related to test results, and offer support. Discuss the implications of abnormal test results on the patient’s lifestyle. Provide teaching and information regarding the clinical implications of the test results, as appropriate. Educate the patient regarding access to appropriate counseling services. Provide contact information, if desired, for the Celiac Disease Foundation (www.celiac.org) or Children’s Digestive Health and Nutrition Foundation (www.cdhnf.org).
  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

  • Related tests include albumin, biopsy intestine, biopsy skin, calcium, capsule endoscopy, colonoscopy, d-xylose tolerance test, electrolytes, fecal analysis, fecal fat, folic acid, immunoglobulins (IgA), iron, and lactose tolerance test.
  • See the Gastrointestinal and Immune systems tables at the end of the book for related tests by body system.