Food sensitivities (IgG) are one of the most common adverse reactions that individuals can have to food. What distinguishes |food sensitivities from food allergies is the speed and type of reaction that is caused. Food allergies are immediate typically atopic reactions; whereas |food sensitivities are delayed and gradual reactions.
Testing for Food Sensitivities
Suspicion of food sensitivities is commonly based on a thorough history, physical examination, and signs and symptoms that are commonly related to food sensitivities. Diagnostic testing includes:
IgG Blood Test
An IgG blood test can be done using different diagnostic processes. The following chart outlines the two main assays, or laboratory testing processes that are used., 
Comparison of ALCAT and ELISA IgG Testing
||Cellular Activation Assay (ALCAT) also known as cell size variability method
||Immunochemical in-vitro Assay (IgG-ELISA)
|| Whole blood
| Test measures
|| Activation of neutrophil granulocytes and other phagocytic cells. Measures leukocyte cellular re-activity.
|| Quantification of antige-ginding IgG-antibodies in serum
| Parameters measured
|| Activation of neutrophils by IgG, IgA and immune complexes, complement, mediators or drugs
|| Amount of specific IgG (or IgG-isotype) that are bound
| Assay time
|| 1-2 hours
|| 2-3 hours
|| All water soluble antigens. Complex mixtures as food extracts can be used, no bias on molecular size, no limitation by chemical nature.
|| Antigens have to be immobilized on a surface and typically are glyco-proteins.
|| Cellular assay, mimics the inflammatory situation in gut. Activation of a large percentage of the cells can be seen. Fast. Simple experimental procedure. Wide range of antigens (food, drugs, chemicals). Technical equipment might be supported by in-house technician.
|| In-vitro assay, using a well established procedure. Technical equipment available in most immunological and diagnostic labs. Easy shipment of samples. Reported "units" suggest precise data. Long-term storage of samples allows longitudinal studies or repeated measurements. Wide dynamic range, wide range of antigens available.
|| Blood has be drawn by experienced personnel. Fast shipment of samples on room temperature or 4 degrees C necessary. Long-term storage of samples impractical. As results in given ranges, minor measured differences may result in "large" reported differences in borderline cases. Re-activity of cells might be influenced by multiple parameters, including patients medication and shipping conditions. Specific technical equipment necessary.
|| The measured antibody titers may not allow a correlation to the inflammatory process as a solid phase assays, specifically if optimized for low titers, tend to measure low-avidity and cross-reactive antibodies. Also an IgG-ELISA does not detect IgA antibodies, the dominant class of antibodies in gut, and does not differentiate between inflammation-driving (IgG1, IgG3) and antigen-capturing IgG isotypes. Risk of a high number of false positives.
- ↑ Trevorrow M, Marsden T. Summer 2012 Food Allergies and Sensitivities: Observing the Complete Picture Vital Link;19(2):33-39.
- ↑ http://www.alcat.com/ ALCAT Testing