ImmunoCAP Specific IgG measures antigen-specific IgG antibodies in human serum and plasma. Specific IgG comprises antigen-specific antibodies of immunoglobulin class G. These antibodies are part of the natural defense system of the body and develop in response to contact with foreign substances.
The presence of IgG antibodies specific to a certain antigen is a marker of exposure to that antigen. Furthermore, the level of specific IgG in serum usually reflects the extent of exposure to that antigen. Measuring specific IgG antibodies may provide a range of valuable clinical information in several fields.
In allergic disease, specific IgG is used:
- In clinical studies with asthma, rhinitis, urticaria, eczema and gastrointestinal disorders
- As a marker for exposure in different lung diseases, e.g. allergic alveolitis, aspergilloma and aspergillosis
In monitoring immunotherapy, increased levels of specific IgG:
- Show a general (but not definitive) correlation with clinical outcome
- Show that the immune system is responding to the therapy
Expected test values
There is no common cut-off value for specific IgG antibodies, as these are markers for antigen exposure and are not directly related to the disease. Results vary both within and between antigens. Geographical variations are also important, as are individual levels of exposure.
To determine if levels are increased, the reference level of specific IgG antibodies to a certain antigen should be measured in a number of samples from normal healthy persons and, if possible, compared with the levels in a group of patients.
Specimen collection and preparation
- Collect blood samples and prepare serum or plasma according to standard procedures
- Keep specimens at room temperature (RT) for shipping purposes only
- Store at 2 °C to 8 °C for up to one week, otherwise store at –20 °C
- Avoid repeated freezing and thawing
The test technology is based on an extremely high total binding capacity, achieved through a high binding capacity per mg cellulose in combination with an optimal amount of cellulose in each solid phase. This ensures binding of all relevant antibodies, regardless of antibody affinity still giving low non-specific binding.
The ImmunoCAP solid phase consists of a cellulose derivative enclosed in a capsules. The hydrophilic, highly branched polymer provides an ideal microenvironment fo rallergens, binding them irreversibly while mainitaining their native structure.
The test is designed as a sandwich immunoassay.
The antigen of interest, covalently coupled to the solid phase, reacts with the specific IgG antibodies in the patient sample.
After washing away non-specific IgG antibodies, enzyme labelled antibodies against IgG are added to form a complex.
After incubation, unbound enzyme-anti-IgG is washed away and the bound complex is then incubated with a developing agent.
||After stopping the reaction, the fluorescence of the eluate is measured. The higher the fluorescence, the more specific IgG antibodies are present in the sample.
As in all diagnostic testing, a definitive clinical diagnosis should not be based solely on the results of a single test method. A diagnosis should be made by the physician after evaluation of all clinical and laboratory findings.