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• Allergen Specific IgG4(Foods and Inhalants)
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Allergen Specific IgG4 (Foods and Inhalants)

Update on the Value of Allergen Specific IgG4 Testing in Patients with Adverse Reactions to Foods

Reactions can vary from mild food intolerance to a severe anaphylactic response often of the type found in patients with elevated levels of allergen specific IgE antibody.

Case in point:

A 62 year old woman with swelling of the lips and tongue after ingestion of banana. This patient's reaction was so severe that the treating physician initially ordered testing for IgE antibody to banana, expecting to confirm that her reaction must be due to an elevated measurement of IgE similar to scores seen in his peanut sensitive patients. To his amazement, the patient had no detectable levels of IgE reactivity to banana!

MRT Laboratories, Inc. then performed an allergen specific IgG4 assay for banana. The result was surprising. She had extremely high levels of banana IgG4. The result was well above the 10 ug/ml that has been reported by others with adverse reactions to milk and other food intolerances. Our lab has observed similar antibody responses in food sensitive patients; i.e. low allergen specific IgE and high allergen specific IgG4.

Laboratory data suggests that levels above 10 ug/ml represent an extraordinary immune response to the specific food antigen.

General information about IgG4 use:

Many studies have been carried out to establish the clinical role and usefulness of IgG4 testing. It is well known that the IgG4 measurement has been a useful indicator for the effect of hyposensitization therapy. IgG4 seems to play the role of blocking antibody in allergen immunotherapy. In contrast, in food induced allergy reactions IgG4 may have a provocative role. High levels of IgG4 antibodies to foods have been observed in atopic eczema patients as well as in patients with asthma, celiac disease, chronic rhinitis, irritable bowel syndrome.

Since IgG4 antibodies may be associated with delayed reaction to foods, it has been suggested that IgG4 testing may assist in confirming food sensitivity in IgE negative patients.

MRT Laboratories Inc. has identified that the rate of positive results is highest for dairy foods, eggs and high fiber foods, such as legumes, grains, banana, and pineapple. The allergen specific IgG4 assay may be ordered for individual allergens as well as suggested and/or custom panels.

Specimen requirement: 1 ml serum is sufficient for 90 tests.

Depending on exposure, fish and shellfish may be added to the suggested panel. Custom Panel requests are dependent on the individual patient's diet.

The interpretation of a positive test result by the practitioner should always be correlated with the history, physical and clinical symptoms of the patient.