IgG/IgG4 Test

The IgG test (IgG/IgG4 test) is a laboratory medicine procedure that can be used to diagnose food intolerance. With the help of the test procedure it should be possible to draw conclusions about IgG-mediated reactions of type III according to Coombs and Gell. Almost any food can lead to an antibody-mediated immune response in many patients due to intolerance, resulting in massive symptoms. According to the definition of the European Academy of Allergy and Clinical Immunology (EAACI, 1994), the following reactions after ingestion of food are called food intolerance or food intolerance reaction:

  • Toxic reactions: Food poisoning
  • Non-toxic reactions
  • non-immunological reactions
    • Enzymatic intolerances
    • Pharmacological intolerances
    • Intolerances to food additives
  • immunological reactions

The ingestion of the intolerant foods can cause chronic inflammation, some of which can not be detected by conventional methods. To detect the intolerance of each food, antibody detection is analyzed by immunoassay (antibody binding test).

Indications (areas of application)

  • Abdominal pain and discomfort – based on food intolerance, immune reactions may be associated with inflammatory processes and cellular hypoglycemia, which can cause significant pain. In the context of celiac disease, based on immunological intolerance of the components of gluten, there may be damage to the intestinal mucosa, which can cause severe pain.
  • Bloating – as a typical symptom of food intolerance is the feeling of fullness.
  • Flatulence – as a result of intestinal dysfunction due to food intolerance, there may be severe symptoms of flatulence and bloating (meteorism)
  • Recurrent (recurrent) diarrhea (diarrhea) – due to altered absorption properties of the intestine, diarrhea symptoms occur more frequently
  • Myalgia (muscle pain) and arthralgia (joint pain).
  • Cephalgia (headache) possibly also migraine
  • Behavioral problems in children

Before the examination

Medical history – medical history plays a crucial role in the diagnosis of food intolerance:

  • How often do the symptoms of food intolerance occur?
  • What foods trigger the reaction?
  • What is the temporal relationship between the reaction and food intake?
  • Are there influencing factors such as coffee and alcohol consumption?
  • Do the symptoms occur depending on physical exertion after food intake?
  • Are there predisposing factors such as other allergies?

Use of other testing procedures:

  • Prick test – using a collection of the most common food allergens, a food allergy can be suspected by dropping a potential allergen and then scoring the upper layers of the skin. A positive reaction to a solution of a food placed intradermally (in the dermis) in the prick test is not equivalent to an allergy.
  • Atopy patch test – this is a form of epicutaneous testing in which, in order to detect food intolerance, potential allergens that can trigger an immediate-type reaction according to Coombs and Gell are applied over the cutis (cutis lat. skin consists of: epidermis/upper skin and corium/leather skin).
  • Provocation test – this test procedure represents the gold standard because a reaction to a food represents an allergic or pseudoallergic reaction. The patient and, if applicable, the investigator are unaware of the food the patient is ingesting. However, it is problematic that an allergic reaction can occur, which can lead to anaphylactic shock.Therefore, this test must be performed only by allergy-experienced physicians who can also perform appropriate emergency measures.
  • Diets – with the help of omission and addition diets can be concluded food intolerances.

The procedure

The IgG test is based on the use of the ELISA procedure. The ELISA is an immunoassay, which is an antibody-based detection method. With the help of special search antibodies, substances can not only be detected but also quantified. The binding of the search antibody to the sought substance, which represents the antigen, results in a complex that can later be stained depending on the method. Specifically, the IgG test looks for IgG antibodies that are directed against various foods and can trigger an immune response in the body. The patient is then given a list of foods that promote the release of IgG antibodies. Arguments for the IgG test

  • Publications from the 1980s have shown that antigen-specific IgG4 can promote histamine release from basophilic granulocytes. Histamine is the most important factor in acute allergic reactions.
  • IgG testing is indicated (indicated) when celiac disease is suspected and IgA deficiency (selective IgA deficiency in the body) is present, according to various studies.
  • Avoidance of the respective intolerant food components often has a positive impact on associated chronic diseases such as atopic eczema (neurodermatitis) or osteoarthritis (degenerative joint disease).

Arguments against the IgG test

  • Various allergist associations warn against overestimation of the diagnostic value of IgG or IgG4 tests.
  • The IgG4 test for IgG4 in the blood against various foods is complex, because hundreds of food components can be responsible for an allergic reaction.
  • Positive results in the IgG4 test correlate only to a small extent with clinical symptoms, so there is insufficient specificity (probability that actually healthy people who do not suffer from the disease in question are also detected as healthy in the test).
  • Too few studies with an adequate design are available to support the validity of IgG testing.
  • According to current scientific findings, the formation of IgG4 against food components represents a physiological response and in no way indicates intolerance. Instead, IgG4 is thought to play an important role in the induction of immune tolerance to food components.

After the examination

After testing is complete, the patient is given a list of foods to avoid to prevent a food intolerance reaction.