|The Allergy Center|
Skin tests, allergy shots, antibodies to food, RAST, IgG4 antibodies,Dermatitis Herpetiformis, IgA skin deposits,Diet Revision as
Diagnosis of Allergy
The desire for simple, office or laboratory test for allergy is easy to understand, but difficult to fulfill. No single test will ever reveal the complex and variable nature of allergic reactivity. The lack of specific tests for different kinds of allergy have hindered progress in this field.
Skin tests are best used to diagnose airborne allergens which cause hay fever. There is a convenient correlation between nose-reactive IgE and skin-reactive IgE . By introducing tiny amounts of suspected antigens into the skin, a local wheal and flare reaction, similar to a mosquito bite, is produced if reactive IgE is present on skin mast cells. The association of hay fever and some asthma, and skin tests with allergy practice was further confirmed by the relative success of "allergy shots". These shots came to characterize the allergist's office; other aspects of allergy practice often were neglected. Allergy shots are immunological treatments. The immune response to any reactive substance can be modified by giving repeated challenges of the reactive substances. Serum assays of IgE antibodies are useful in diagnosing type 1 food allergy. In a study of patients with asthma, and atopic dermatitis, plasma histamine and tryptase levels rose in the group with immediate reactions to food challenges. An elevated plasma tryptase level is thought to indicate mast cell activation. The authors noted subjects who had delayed symptoms - diarrhea at 4 hours, erythema and urticaria and 8 hours, and exacerbation of atopic dermatitis at 24 hours had slow or low histamine responses with no tryptase elevation.
The idea that standardize protein extracts of foods would be the most reliable and "scientific" tests for food allergy have been thwarted by observations that skin tests with fresh-extracts from food correlated better with symptoms on challenge testing. Food antigens can be complex, multiple, and may not survive processing into standardized extracts. In a review of studies of type 1 reactions to vegetables and fruit, mouth and tongue symptoms dominated. Systemic reactions included urticaria, angioedema, asthma, rhinitis, headaches, and itchy hands. Testing with commercial food-protein extracts was found less reliable than using the fresh food. Skin tests do not reveal the more complex forms of food allergy. Some labs offer other tests for food allergy, including IgG RAST, and immune complex assays. While these tests produce interesting results, they are expensive and do not answer the main question - what should the patient eat?
The reality that I confronted for many years was that very sick patients would get better with diet revision that excluded gluten and other food ingredients regardless of their laboratory tests or biopsy results. My attitude is that positive antibody tests are interesting findings in research, but may not be helpful in the management of sick patients. You have to know that are four major classes of antibodies and many subtypes. It is estimated that one person can make a large number of antibodies that interact with a million or more targets. Every person has circulating serum antibodies to some food proteins, but there is no easy cause and effect connection between the amount of antibody and the activity of a disease. I concluded that antibody test results were not helpful in directing treatment. The prevalent attitude of physicians is that proper diet revision is too difficult to undertake and they would not consider diet revision to be a suitable experiment to undertake when a patient was chronically ill and not benefiting from treatments offered. I believe that the primary duty of the physician is to find an effective treatment for disease.
The IgE model of allergy inspired development of antibody-measuring laboratory tests. The idea was to show the affinity of circulating antibodies to different antigens. RAST has been used instead of, or in addition to, skin prick and scratch tests to assess food allergy. Variations of the RAST bear the acronyms ELIZA, FAST, and MAST. These are all tests for antibodies directed at selected antigens. The principles of RAST testing for IgE are applied to the measurement of other antibody types. Some studies suggest frequent IgG responses to food antigens. Tests measuring food-antigen specific IgG have been offered with an impressive computer-report of "food sensitivities". The levels of food-specific IgG are listed, and avoidance of foods that cause increased antibody levels is advised. Helpful food lists and food rotation instructions accompany some of the lab reports. It would appear that the problem of food allergy diagnosis is solved. Again, this simplistic approach to food allergy diagnosis is bound to mislead. While it is possible that avoidance of IgG-positive foods will be helpful, we do not know whether that avoidance will really resolve the illness problem. IgG is known to play a protective role and high levels may mean less disease. In my experience with the IgG RAST, the predictive value for food reactions is limited.
Kumar et al found IgG4 antibodies to wheat, beef, pork, lamb, soya beans and egg in irritable bowel patients. Levels of IgE antibodies were similar to controls.
Dermatitis Herpetiformis is characterized by the presence of IgA deposits in the upper dermis of skin Karpati suggested that DH develops in people with celiac disease who also produce IgA antibodies to epidermal transglutaminase an enzyme found in found in skin and other tissues.
Tests, such as anti-gliadin, anti-endomysium, and anti-transglutaminase antibody estimation can be used as screening tests in groups considered to be at risk of celiac disease. These include first-degree relatives of celiac patients and patients with irritable bowel syndrome, arthritis, diabetes mellitus, iron-deficiency anemia, epilepsy, cerebellar ataxia, autoimmune diseases, depression, weight loss and malnutrition. While these antibody tests are useful in identifying potential celiacs, they should not be used to “rule out’ gluten-related diseases.
Ciclitiria al demonstrated that jejunal mucosal biopsy specimens cultured in vitro secreted anti-gliadin antibodies of the IgG and IgM types. Circulating anti-gliadin antibodies (IgG) were demonstrated by the ELIZA technique in the serum of 36 of 44 patients with celiac disease. They also found that half the patients with other gastrointestinal disorders had raised titers to alpha-gliadin. The measurement of antigliadin, anti-reticulin R1 and antiendomysium antibodies can be used as screening tests. Anti-reticulin R1 (ARA-R1) and anti-endomysium (AEA) antibodies may be more reliable markers than anti-gliadin (AGA) antibodies. Transglutaminase antibodies (TGA) are now popular markers of CD. Transglutaminase is a normal enzyme and it appears to be the antigen target for AEA.
Patients are Frustrated
The difficulty in diagnosing food allergy and other food-related problems in clinical medicine and disputes within the allergy community have left many patients suffering, frustrated and confused. At the same time as physicians default in the diagnosis and treatment of food-related illnesses, many non-medical practitioners have launched careers in the food and chemical "sensitivity" business, using diverse, sometimes curious and bizarre methods, dubious tests and questionable treatments. Even well-intentioned efforts to diagnose and treat food allergy are often based on faulty premises and fail to deliver proper results.
Food allergy is diagnosed by physicians who understand the multisystem, polysymptomatic patterns of illness involved. These patterns are revealed by a careful history, and the diagnosis made on clinical grounds. The pattern of food-related illness, the sequence of symptom production, and the distribution of disturbances in the body can be explained if complex causation is assumed. Without a well-equipped research laboratory it will not be possible to actually measure the pathophysiological events.
Bad and Bizarre TestsOne frustrating aspect of working with food-related diseases is that confused and confusing people greet you at every turn. Food allergy, sensitivity and intolerance have are topics that have been obscured by nonsense and confusion for several decades. MDs, by in large, remain ignorant of delayed patterns of food allergy and are often not helpful to patients who seek their advice. A series of dubious testing procedures for “food sensitivity” have flourished in the non-medical sub-culture. A number of bad and bizarre "tests and treatments” have caught on as quick and easy methods of dealing with complex problems and have contributed to the aversion some physicians display toward the subject of food allergy. In any other context, some of these tests would be bad jokes or ludicrous charades. What makes the popularity of these fake tests a serious matter is that patients are suffering and are eager for solutions to their chronic health problems. Because they not getting help from qualified physicians, they are vulnerable to anyone who seems at all plausible and offers tests and treatments for food problems. Here are some examples of doubtful and bizarre tests:
Provocation Tests by InjectionProvocation tests by needle injection of food proteins into the skin have been used to determine food sensitivity. While these test are the most plausible of the group of the bad and bizarre tests, they do not do what they promise and should not be used to determine what the patients can eat. The intradermal (ID) injection test will occasionally show a delayed, cell-mediated response in 24-48 hours. Symptoms may develop as injected antigen reacts with skin mast cells, or reaches circulating basophils and triggers an amplified, immediate alarm response. There is no question that injected antigen can sometimes demonstrate symptom production in the allergic patient. Indeed, every allergist is concerned about triggering life-threatening anaphylactic reactions with any injection. If major symptoms do occur with one injected antigen, further testing is invalid for several days.
Clinical ecologists have claimed to "neutralize" the reaction by injecting further doses of antigen at different concentrations, and often test many substances in one session, lasting several hours. We do not believe any meaningful conclusions can be drawn from these testing marathons.
The subject tends to have fluctuating, confusing sensations, and is extremely vulnerable to suggestion from the testing person. The ID provocation test is not reliable in predicting responses to foods actually eaten, and should not be used as the basis for recommending diet revision. A small study by Jewett and associates in California questioned the validity of provocation tests; 18 patients were tested by this method and they concluded that subjects had difficulty differentiating active from inactive solutions and that the neutralizing effect was not related to the concentration of the active ingredients. This study failed to support the method of provocative-neutralization "allergy" testing - fair enough, but an associated editorial in this esteemed journal used this result to further a widespread prejudice against food-sensitive patients; with the byline, "Food Sensitivity or Self-Deception", the editorial hints darkly that all patients with food allergy are dupes. We have noticed over the past 15 years, that the mention of food allergy invites prejudiced if not hostile opinions from many members of the medical establishment. Indeed, some of the worst examples of dogmatic and irrational thinking can be elicited from MDs by food allergic patients. The only conclusion we can reach about provocation tests and this study is that if subjects are asked to sit in a room for several hours after breakfast or lunch, receiving a variety of injections, with a variety of distractions and suggestions, explicit or implicit, from testers and other subjects, everyone will come to the wrong conclusions about what is really going on. The authors of this study did not seem to realize that any group of subjects sitting in a room will report symptoms, if asked. This is not a mysterious "placebo" effect; but the "noise" of each person's body, which becomes apparent to everyone who sits quietly and does nothing for a few hours. They may be reacting to foods they ate before they arrived for the tests.
Cytotoxic TestsCytotoxic tests were offered in the early 80s for definitive "food sensitivity" determination and were condemned by the American College of Allergists as ineffective. Cytotoxic tests expose blood cells to food extracts in a chamber viewed through a microscope; cell counts before and after reveal cell damage. Automation can be applied to cell counting and evaluation with computer print-outs of test results. While the earlier cytotoxic tests have little to offer, more sophisticated analysis of food antigen and blood-cell interactions is always relevant to understanding pathogenic mechanisms. An automated test has been offered as the ALCAT diagnostic system. The ALCAT brochure repeats the understanding that multiple mechanisms are involved in food allergy and that responses to food antigens by various blood components should be measured in food allergic individuals. The predictive significance of these measurements remains to be discovered.
Muscle testingMuscle testing is one of the bizarre charades used to demonstrate "food and chemical sensitivity". The subject is invited to hold a glass vial containing the test substance and the examiner tests the strength of the other arm that is outstretched. Sometimes the subject is instructed to hold the vial over the body part to be tested. Weakness is interpreted as a food reaction, and the subject is advised to avoid the test substance. Variations on this theme have emerged. As a party game, muscle testing could be fun. Anyone who believes that this is a valid test of body physiology needs to be re-educated in biology. Muscle testing is a worthless scam if you are paying real money to be "tested."
Vega MeterA simple resistance meter, dressed up in a fancy box (Vega meter), is used to measure skin resistance between a ground plate and an "acupuncture point", usually at the thumb web. A glass vial, containing test substances, is placed somewhere (it doesn't seem to matter where) in the circuit. Meter readings are interpreted as "positive or negative reactions". The more imaginative Vega meter readers will tell you that they can balance levels of certain substances in your body by doing meter readings and prescribing drops.
You might sign up for a series of tests and treatments and the cost can vary from hundreds to thousands of dollars. Too good to be true? Of course, Vega meters are scams.A pseudo-science explanatory system, referring to "oscillations in the electromagnetic field", confuses and misleads the sincere patient who just wants to get better.
Feathers, Crystals, FantasyWe have seen machines, tests and treatments that go from impressive scams and charades to the ludicrous and ridiculous. One patient, for example, brought 4 pages of food test results from a homeopathic practitioner who used a crystal and a feather to evaluate her food sensitivities. This was a neatly hand-written list showing the many foods tested and her sensitivity to them, presented as a percentage: she was 80% sensitive to milk and so-on. Many balancing potions were prescribed and she was to avoid the foods that had high percentage scores on the "tests". She did improve on this regimen because she stopped eating many problem foods; however, she soon lost her way and became confused about what she should do long-term. We would all like either a futuristic machine that could give us all the answers or the super-human ability to simply write down the reactive repertoire of each person, but the emperor has no clothes! Vega machines, muscle tests, feathers, pendulums and crystals belong in the magician’s bag of tricks or the hypnotist’s stage show but are not part of a sincere practice of medicine, using valid and reproducible techniques. If you have paid real money for these tests and associated treatments, you have been cheated.
Live Blood Cell AnalysisThe idea is that you put a drop of blood on a microscope slide and look at the living cells. This could be a good idea, but there are serious flaws when this procedure is offered as diagnostic test for food allergy or food toxicity. So far, we have not been convinced that any office-based live cell analysis is valid. The analysts, in our opinion would have difficulty identifying which cell types they were observing. They have no way of differentiating cell-damage artifacts from real pathology. Their displays of cell abnormalities appear to be mostly artifacts, and their diagnoses defy biological knowledge. We would bet big money against the reproducibility of this technique. Any takers?
Experienced microscopists know that looking at living specimens under the microscope changes the specimen. Viewing live cells is difficult because they have to be suspended in a nutrient solution, at the right temperature. It is challenging to keep them alive. Heat from the light source tends to dry cells; the water in which they are suspended evaporates and the cells pucker up, change shape and develop abnormal looking membranes. They may stick together. There are artifacts, in other words, that an uncritical observer can interpret as evidence of disease. Even if the lab has expensive equipment and expertise to keep the cells alive and in good condition, the observer has to be familiar with different cell types, understand their morphological characteristics and behavior. There are possibilities for advanced systems of live blood cell analysis. We would like to know more about how blood cells behave in vivo, and it is possible to simulate living conditions under the microscope, although expensive equipment and skilled operators are prerequisites. There are proper techniques for observing how specific living blood cells behave when exposed to specific stimuli. One test, for example, observes whether lymphocytes begin to multiply when they are exposed to an antigen. A clinical test based on this idea could be useful. This is a research project, not a validated diagnostic method and certainly not a technique that can be done by amateurs.
See Diet Revision as Proper Diagnosis and Treatment Combined