All you need to know about allergy testing and intolerance tests
Last Updated: 10th November 2022 · Written by Donna Mastriani
At Lifelab Testing, we ensure that all our samples for our allergy testing and intolerance test are handled with the utmost care, treated confidentially and looked after.
All our Allergy and Intolerance testing products work in the same way. They are immunoassay’s that determine levels of antibody reactivity against specific allergens. We test using a blotting procedure which is very similar to ELISA (which you may see with other providers of similar tests). Western Blotting procedures are commonly used diagnostic tools and provide analytics for many areas of health care and immunology that can aid in diagnosis of medical conditions.
But how do they do this?
In order to measure a specific antibody response, we require several things. A client’s sample, and a panel of specific allergens derived from foods or other triggers (such as pollen or epithelium cells). Then we also need conjugate, wash solution and substrate.
Each client’s sample will be unique to them, and all our testing panels are produced in an identical way by our supplier and adhere to forms of quality control and compliance as an accredited provider of analytical tests. We ensure that every delivery from our supplier confirms to these standards by checking its certificate of conformance. Our supplier also provides us with IgG4 and IgE conjugates and a substrate which also conform to quality control standards, as well as a washing solution.
How many allergens are on a panel will vary based on the test that you purchased but the reaction will be the same.
The first stage of the immunoassay will be to apply a quantity of patient sample (dependent on whether it is IgE or IgG4 and which panel tested based on purchased product) to the testing panel. If there are any specific antibodies present in the sample, specifically relating to those on the panel, they will bind. Every panel also has three control values that will always react the same way with known values.
Next up the panel will require to be washed with the wash solution, this is designed to remove all unbound sample from the panel and prevent non-specific binding to the panel, whilst also not being too abrasive to remove bound allergens and antibodies.
Next the specific conjugate is used. A conjugate has been devised to react to either IgG4 or IgE antibodies. So, if there have been any reactions to the allergens on the panel, the conjugate will then bind to the complex of antibody and allergen. If this happens the complex will be marked by the presence of the conjugate binding. This will be left to react for a period of time.
The next step is to use the wash solution again to remove unbound conjugate.
A substrates job is to make this reaction complex visible for analysis. There are many ways to do this. We use a colorimetric method, which means we apply a numeric value to the shade of a colour.
When we apply the substrate to the panel, if there has been a reaction between a conjugate and an allergen/antibody complex the position on the testing panel will be visibly coloured. If there has been no reaction the substrate won’t react, and the position will remain clear.
The three control areas of the panel will always react in the same manner. These controls correlate to three known values of increasing reactivity. The reaction on the panel is then stopped and then scanned, software analyses the strength of the present colour against these three controls and determines the value of reactivity.
These are then presented as a client’s reactivity profile for the results. The stronger the colour the more concentration of specific antibodies in their blood.