Imagine your pharmacy features a blood pressure measurement device. It has never worked correctly. Sometimes it give incorrect high results, suggesting hypertension. In other patients it misses hypertension completely. You’ve been advised by hypertension experts that this particular model isn’t accurate and shouldn’t be offered to consumers. Despite this, you continue to promote it to your patients, and you use the test results to recommend supplements to treat conditions that may or may not not exist.

Does this meet the professional standards expected for pharmacists? From an ethical perspective, does it respect patient autonomy? My sense is that consumers, ethicists, regulators, and other health professionals would say “no”. Pharmacists have an ethical and professional responsibility to base advice on the best scientific evidence – in this case, to ensure that a service being offered is reliable, accurate, and relevant for making health decisions.

That’s why I’m surprised to see Canadian and American pharmacies are now selling IgG food intolerance tests. Because if you agree that knowingly offering faulty blood pressure measurement tests is unacceptable, you should have just as much concern about food intolerance blood tests. These tests have been available for some time in the United Kingdom. Now they’re in North America. Rexall, the Canadian pharmacy chain, recently started selling the “Hemocode” test which is purported to test for 250 food intolerances:

You might love food, but some food might not love you The HEMOCODE Food Intolerance System can unlock your hidden food sensitivities Speak with your Rexall Pharmacist today to learn about a painless blood test that can identify over 250 common foods that may be causing you unpleasant symptoms such as chronic fatigue, migraines, back pain, fibromyalgia, psoriasis, acne, diarrhea and constipation.

There’s a short video that is very illustrative.

Narrated by a pharmacist, it describes that a simple fingertip blood test is used to screen blood against 250 items. Test results are then reviewed by “naturopathic medical professionals” who will describe the foods and other products that you are intolerant to, and your degree of intolerance. You’re also advised:

Your personalized results also include recommended vitamins and supplements that are uniquely suited to the customer, based on the foods that are suggested to be eliminated from your diet, which are themselves, uniquely personal.

So the $450 blood test, includes dietary change recommendations as well as vitamin and supplement recommendation. Hemocode is an IgG blood test, according to the manufacturer (text now removed; cached version here):

The Hemocode System is a finger prick test that identifies specific immune system-based food intolerances. Everything we eat can elicit a positive or negative reaction in the body. If you are intolerant to a certain food and you continue to eat it, your body will mount an inflammatory reaction which may manifest in a variety of lifestyle-affecting conditions such as headaches, chronic pain, digestive disorders and many other issues The Hemocode food intolerance test is a statistically proven, doctor and pharmacist recommended IgG-related test that determines which foods are causing negative reactions.

There is no published evidence cited on the Rexall site or the Hemocode site that documents how this test have been validated. Importantly, food intolerances are non-allergic by definition. So why test immunoglobulin G (IgG)? IgG molecules mediate interactions of cells with different cellular and humoral mechanisms. IgG antibodies signify exposure to products—not allergy. IgG may actually be a marker for food tolerance, not intolerance, some research suggests:

Children with eczema and egg or milk allergies with higher levels of IgG to milk/egg were more likely to be tolerant of these foods at a later age.

Resolution of cow’s milk allergy is associated with increasing IgG

A study found increasing IgG in patients who underwent oral immunotherapy for milk or peanut allergy

Given the lack of correlation between the presence of IgG and physical manifestations of illness, IgG testing is considered unproven as a diagnostic agent as the results lack clinical utility as a tool for dietary modification or food elimination. So I consulted the medical literature for consensus clinical opinion on IgG blood tests, for tests like Hemocode. I summarized the literature in a lengthy post on the diagnosis of food intolerance and the use of IgG testing over at Science-Based Medicine. Here are the highlights of that review:

From the American Academy of Allergy, Asthma and Immunology & American College of Allergy, Asthma and Immunology: Allergy diagnostic testing: an updated practice parameter:

IgG and IgG subclass antibody tests for food allergy do not have clinical relevance, are not validated, lack sufficient quality control, and should not be performed.

And from the the American Academy of Allergy, Asthma and Immunology (AAAAI) Practice Paper, Current approach to the diagnosis and management of adverse reactions to foods [PDF]:

Some tests are considered unproven in regard to the diagnosis of specific food allergies. Those for which there is no evidence of validity include provocation-neutralization, cytotoxic tests, muscle response testing (applied kinesiology), electrodermal testing, the “reaginic” pulse test, and chemical analysis of body tissues. Measurement of specific IgG antibodies to foods is also unproven as a diagnostic tool.

From the European Academy of Allergy and Clinical Immunology [PDF]:

…testing of IgG4 to foods is considered as irrelevant for the laboratory work-up of food allergy or intolerance and should not be performed in case of food-related complaints.

From the Australasian Society of Clinical Immunology and Allergy (ASCIA):

There is no credible evidence that measuring IgG antibodies is useful for diagnosing food allergy or intolerance, nor that IgG antibodies cause symptoms … Despite studies showing the uselessness of this technique, it continues to be promoted in the community, even for diagnosing disorders for which no evidence of immune system involvement exists.

From the Department of Pediatric Pneumology and Immunology, University Children’s Hospital Charité, Berlin: Unproven diagnostic procedures in IgE-mediated allergic diseases [PDF]:

The determination of specific IgG-antibodies in serum does not correspond with oral food challenges. … Since IgG-antibodies to common dietary antigens can be detected in health and disease, the determination of food-specific IgG is of no clinical relevance and should not be part of the diagnostic work-up of food allergy.

From the Department of Paediatrics, National University Hospital , Singapore, Diagnostic tests for food allergy [PDF]:

INAPPROPRIATE TESTS :Food-specific IgG tests

Unfortunately, the determination of specific IgG antibodies in serum does not correspond with oral food challenges. … Recent studies have shown that the IgG response may even be protective, and thus prevents or protects against the development of IgE food allergy. Hence, there is no convincing evidence to suggest that this test has any diagnostic value for allergy.

From the UK House of Lords Science and Technology—Sixth Report on Allergy:

We are concerned both that the results of allergy self testing kits available to the public are being interpreted without the advice of appropriately trained healthcare personnel, and that the IgG food antibody test is being used to diagnose food intolerance in the absence of stringent scientific evidence. We recommend further research into the relevance of IgG antibodies in food intolerance, and with the establishment of more allergy centres, the necessary controlled clinical trials should be conducted. We urge general practitioners, pharmacists and charities not to endorse the use of these products until conclusive proof of their efficacy has been established.

This is just a selection of the clinical opinions on IgG food intolerance tests – see the post at Science-Based Medicine for the full summary.

Conclusion

At present, there are no reliable and validated clinical tests for the diagnosis of food intolerance. These tests lack both a sound scientific rationale and evidence of effectiveness. Major allergy and immunology organizations around the world advise against the use of IgG testing for diagnosing food intolerance. These tests may lead to unnecessary and difficult dietary changes, with the potential to negatively affect nutritional status – particularly in children. So why are pharmacies offering them? Using IgG test results to guide dietary recommendations and to suggest supplements for consumers makes pharmacists look like quacks, not credible, science-based health professionals. Whether it’s ignorance of the science, or indifference to the evidence, when it comes to pharmacies selling IgG food intolerance tests, consumers are quite literally paying the price.