– Molecular diagnostics is a milestone in allergology. Today, the information that the patient is allergic to peanuts tells us little. On the other hand, the information that he is allergic to Ara h 2 is very much… We are talking with Dr. Emilia Majsiak, MD, PhD about a new chapter in diagnosing food allergy.
Statistics show that food allergy is the fastest growing form of allergy in the population of our country. Can we identify the reasons?
We cannot speak of one specific cause. The observed increase in the incidence results mainly from the unfavorable interaction of genetic and environmental factors. We know that the risk of allergies is much higher in people with a family burden and can be as high as 60% if both parents are allergic.
The second very important factor is the rapidly progressing civilization development: environmental pollution, cigarette smoke, processed food, higher hygiene standards characteristic of developed societies. All of this can cause our immune system to recognize certain foods as ‘hostile’ and to start producing antibodies against them.
Can food sensitization have different symptoms in different patients?
Yes, one person may experience vomiting and another may have a rash. In the case of a mild course of food allergy, the most common symptoms are nausea, vomiting, abdominal pain, but also skin changes, stuffy nose, and lacrimation. However, severe course includes hives, breathing problems, swelling of the tongue or throat, fainting. The most dangerous manifestation of allergy and what we fear the most is anaphylactic shock, i.e. a state of immediate threat to life.
There are many food allergy tests on the market – are all of them reliable?
Unfortunately, no – many of the available methods are not applicable in the diagnosis of allergies, and even proved to be useless in diagnosing food allergy, and yet they are recommended by people who are not allergists. An example is the ALCAT test, popular in the 90s in Poland, which never obtained the approval of the American and European Academy of Allergology and Clinical Immunology or the Polish Society of Allergology.
Also, the effectiveness of the MRT test, which is based on the measurement of the total volume of white blood cells and platelets, has not been confirmed by independent studies. The same applies to the VEGA test, the study of the composition of the intestinal microflora, bioresonance, hair and nail analysis or tests for the so-called IgG-dependent food intolerances. All these procedures may mislead patients, exposing them to costs and harmful dietary restrictions, but most of all to diagnostic delay and treatment delay.
So what should the correct diagnostic path look like?
The first thing you should do is visit an allergist who will interview you for allergies. It will then decide whether or not to perform diagnostic tests to identify the foods responsible for the patient’s hypersensitivity reactions. These can be skin tests or blood tests. If we manage to detect the causative agent, the situation is simple – we simply eliminate the allergenic food from the diet, or check the risk of cross-allergies.
Can we do a blood test for a specific allergen or better a panel for a specific number of allergens?
It depends – for example, if you feel unwell every time you eat a salad with carrots, you can do a single test and test only E (IgE) antibodies to carrots, but if you do not fully recognize the factor causing the symptoms or these foods there are many that cause symptoms – for example, a food panel containing 20 or 30 allergens can be made. We can also perform a wide panel – comprehensive molecular tests, in which we will examine not only allergens, but also their protein components.
What does this give us?
Let’s stick to the example of carrot – firstly, we will find out which protein in the carrot sensitizes you, and secondly, we will check which group of proteins it belongs to. Let us assume that you sensitize Ms. Dau c 1 protein, which belongs to the PR10 group. Knowing this, the allergist may suggest that the patient watch for harm from other foods containing “nearly identical” proteins from the PR10 group. So in this case: is it harmless, for example, from apple, celery and if there are no symptoms when birch dusts. This additional information makes it possible to precisely establish the diagnosis, and then to formulate therapeutic and dietary recommendations.
In what situations can molecular diagnostics prove particularly useful?
Molecular tests are recommended for people who find it problematic to identify the source of their allergy, as well as for patients who have experienced severe reactions after contact with a given allergen, such as anaphylactic shock. Imagine this situation: the patient got a shock while on vacation. Romantic scenery: sunset on the seashore, sweetheart by your side, a plate full of fish and seafood, and an ambulance.
Fortunately, the man is saved. After returning home, she goes to an allergist, but her skin tests for fish and seafood are negative. How it’s possible? The study Variability of allergens in commercial fish extracts for skin prick testing, published in 2019 in the journal Allergy, showed that out of 26 commercially available fish allergen testing, only six of them contained the main allergenic fish protein – parvalbumin, which carries with it high risk of anaphylaxis. A person allergic to this protein can get a shock from just inhaling over a pan with fried fish. So knowing what kind of protein it is and what is the risk of serious reactions can save the life of a patient with food allergy.
There are several tests available for molecular diagnostics: ISAC, ALEX and FABER – are they different?
Yes, the first available test that allowed to determine only allergen molecules was the ISAC test, while the FABER and ALEX – this is the next, third generation of tests in allergology, which apart from molecules also allows you to test extracts. What additionally distinguishes the FABER test is the communication platform to which both the doctor and the patient have access. It contains information about all the molecules and extracts that were positive in our study.
We will find out what kind of protein it is, what group it belongs to, whether it carries the risk of anaphylaxis, whether it is thermostable or thermolabile. The last piece of news is very valuable, I will present it on the basis of a patient allergic to cow’s milk proteins: a person allergic to cow’s milk whey proteins: alpha-lactalbumin, beta-lactoglobulin, bovine serum albumin and lactoferrin may tolerate milk after cooking or baking, in turn, a patient allergic to casein, which is a thermostable protein, no longer.
This means that the elimination diet of each cow’s milk allergy patient may be different – one more restrictive and the other less. There are also other interesting facts: there are such molecules, e.g. in a peach, that after eating this fruit, no symptoms may occur, but if a person allergic to this molecule will eat a peach and go for a run, severe symptoms and even shock may occur. I am talking about the so-called cofactors, i.e. factors that trigger anaphylaxis. These include, among others: exercise, alcohol, menstruation, non-steroidal anti-inflammatory drugs (NSAIDs).
Will the FABER test show us?
The test can show in the cited example that there are E antibodies to peach and more specifically to the Pru p 3 protein which belongs to the LTP protein group. An allergist who interprets the result of this test, seeing this information, knows that patients allergic to this group of molecules may not have symptoms, but in the context of cofactors: physical activity, alcohol or severe stress, even strong systemic reactions may occur.
So you can say that we have entered a new era in the diagnosis of food allergies, and 8 great allergens are going away …
We can definitely say that molecular diagnostics is a milestone in allergology. Today, the information that the patient is allergic to peanuts is too general. Molecular diagnosis of allergies gives us a broader picture of the patient’s sensitization. We get additional information that brings a lot to a person with this allergy – because in the case of allergy to the proteins of the peanut Ara h 1, Ara h 2, Ara h 3 or Ara h 6 there is a high risk of a severe reaction or even shock, while allergy to Ara h 8 peanut is most often associated with a local response: itching, swelling of the mouth, i.e. oral allergy syndrome (OAS).
In the era of molecular diagnostics and the knowledge it allows, people allergic to peanuts, fish, milk or other foods do not have to tremble every time they reach for a dish that they have not prepared themselves. They can check which molecule sensitizes them and what effects it can cause, whether it may be abdominal pain, bloating and some discomfort, or whether eating such a meal may end tragically …
Are there any limitations with molecular diagnostics?
At present, about four thousand proteins are described, of which about 170 are available for routine diagnosis. Thus, it is possible that the patient will obtain a positive result for a given allergen extract, but in the test the molecules of this allergen currently available for testing will be negative . For this reason, testing allergen extracts together with molecules increases the diagnostic accuracy and complexity of the test. On the other hand, we are talking about a young field that is constantly developing.
The FABER test has been available since 2016, and ALEX since 2017 – so this is new knowledge that we all learn, which also requires commitment, time and attention to efficiently interpret the results of molecular tests. Therefore, it is very important that the patient does not interpret the test result for himself. The results of such tests should be interpreted by a specialist in the field of allergology. This is the latest knowledge in allergology, and only an allergist doctor can correctly interpret these results.