Allergix IgG4 Food Antibodies 90 - Serum

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Turnaround Time: 7 Days
CPT Code:

86001 (x90)



Test Type: Kit Based, Serum


Circulating IgG4 food antibodies are not diagnostic for a specific condition but indicate an immune response to the presence of food antigens. IgG4 antibodies are produced in a delayed hypersensitivity reaction, which can occur one to seven days after exposure to the offending food antigen. These reactions are difficult to detect since there may be no obvious association with the offending food. Commonly reported symptoms for elevated IgG4 responses involve GI tract, skin, nose, and throat. In contrast, the immune response could be a normal response that would not necessarily cause symptoms. Therefore, test results should always be viewed in the context of the overall clinical picture.

Conditions associated with IgG4 food antibodies:

  • Eosinophilic esophagitis
  • Irritable bowel syndrome/ GI symptoms
  • Crohn's disease

Of the 5 classes of antibodies, immunoglobulin G (IgG) is the most abundant circulating antibody, making up 75% of antibodies. The other classes of antibodies include IgE, IgA, IgM, and IgD. IgG has 4 subclasses including IgG1, IgG2, IgG3, and IgG4 making up 66%, 23%, 7%, and 4% of the IgG antigen pool respectively.

IgG4 is unique compared to the other subclasses. It acts as a blocking antibody to the allergy-producing IgE antibody, and with the IgE antibody, is considered part of the Th2 response. Increases in IgG4 levels correlate with improved clinical responses since it blocks the IgE anitbody allergic response; it is involved in establishing immunologic tolerance to that food. IgG4 does not activate complement compared to IgE3. Some speculate that IgG4 may be produced initially to attenuate IgE-mediated disease, but ultimately results in a pro-inflammatory process in susceptible atopic hosts.

Collection Details:

Patient Preparation:

  • It is not necessary to have the patient fast.
  • It is not necessary to discontinue nutritional supplements prior to this test. Abnormalities that may be found will reveal special needs that have not been met by
    recent dietary and supplemental intake.
  • The use of immunosuppressive drugs, like cortisone, can give false negative test
    results. Discontinue the use of such drugs for 60 days before testing to allow
    antibody reactions to be seen.

Collection Instructions:

1. Write patient’s first and last name, date of birth, gender and date of collection on the Test Requisition Form (located in the pouch on top of the Specimen
Collection Kit Box), as well as all transfer tubes, using a permanent marker.
• IMPORTANT: To ensure accurate test results you MUST provide the
requested information.
2. Red/gray top serum separator tubes and red top clear transfer tubes
» Draw one red/gray top serum separator tube completely. Exceptions: Draw
2 red/gray top serum separator tubes when ordering IgG4 with IgE Foods
» Place tube(s) upright in a rack at room temperature no longer than
20 to 30 minutes.
» Centrifuge the red/gray top serum separator tube(s) for 15 minutes. The serum
must be free of hemolysis or red blood cells.
» Pipette 3 ml serum, using a fresh disposable pipette, into the red top clear
transfer tube(s). A total of 6 ml of serum is required when ordering IgG4 with
IgE Foods (#0270)*» Discard the serum separator tube(s) after pipetting the serum into the transfer