Food Allergy ELISA IgG Tests Fall Short for Diagnosis
Over the past 15 years, the use of IgG testing to determine food allergies has been met with controversy. There is good reason for this. Research now shows that IgG testing offers little in the way of concrete diagnostic accuracy for food allergies and food sensitivities.
Today, numerous clinical practices regularly diagnose food allergies using IgG testing offered by diagnostic labs under a variety of trademarks. Recently drugstore pharmacies have joined the fray, offering in-store blood draws with follow-up test results.
IgG stands for Immunoglobulin G – an antibody protein produced by the immune system’s B-cells. Food allergies are typically diagnosed with the presence of IgE antibodies, but IgG’s link to food intolerance or weak allergies has yet to be scientifically established.
While a few small studies have shown a possible correlation between self-reported food allergy and IgG testing with ELISA, most of the food allergy societies such as the European Academy of Allergy and Clinical Immunology and the American Academy of Allergy, Asthma and Immunology (AAAAI) have resoundingly rejected the accuracy of IgG testing to confirm a food intolerance.
These agencies have surveyed the evidence, and found that positive IgG results can just as easily indicate a food that has been eaten regularly as much as it might indicate a food intolerance. But the evidence either way has been weak. Until now.
IgG testing has finally been put to the (large study) test
The controversy was recently put to the test in a very large study from researchers at the International Medical Center of Beijing’s PLA General Hospital. The researchers conducted a multi-center study of 21,306 adults from around China.
The researchers stated this about the importance of their study:
“Although commercial laboratories worldwide are currently offering broad-scale testings for serum levels of food-specific IgGs to the public, to our knowledge, the study described here is the first representative cross-sectional study to address the distribution of food-specific IgGs and its relationship to chronic symptoms in a large population.”
The study population composed of both healthy people and people with reported food intolerances. The researchers gave all the subjects blood tests for 14 food-specific IgG antibodies using ELISA – which stands for enzyme-linked immunosorbent assay.
The foods tested included wheat, mushrooms, eggs, fish, chicken, beef, soybeans, rice, tomato and others.
From the 21,306 subjects tested, 5,394 of them were randomly selected to complete surveys on their diets and their food tolerance-related symptoms.
The researchers then calculated the results of the surveys with the IgG testing to determine if there was a correlation between the intolerant foods reported by the patients with the food-specific IgGs gained from the test results.
No correlation found between higher IgG levels and food intolerances
Instead of finding the IgG test results closely matching those food intolerances reported, the researchers instead found that higher IgG test results often related to foods they were eating without intolerance symptoms, and lower IgG results for foods they reported as being sensitive to.
In fact, the results were so varied that the researchers could not find any correlation between the IgG results and the reported food allergy. They found that higher IgG levels were found among women and age – older people had more food-related spikes in IgG levels.
More revealing was that higher IgG levels were also distinctly related to where the subjects lived and that region’s general diets. In those areas where more corn consumed, for example, more people had higher IgGs related to corn – regardless of whether they reported a food intolerance to corn or not.
In other words, the IgG testing revealed nothing about food intolerance among the population.
And healthy people can have similar levels of heightened IgGs as those who have food intolerances:
“In summary, the present study demonstrates for the first time that food-specific IgG serum concentrations are variable in both healthy and symptomatic Chinese adults. “
This scenario is called a false-positive. When a test result that is being promoted to indicate a particular condition shows a positive result for a person who does not have that condition, the result is called a false-positive.
And the many cases in this study that had positive test results for foods they were not sensitive to are, by definition, false-positives.
This also explains the scenario of a patient receiving a IgG positive test result for a food they are sensitive to. Because there is a history of eating that food, there is a sensitivity. And because there is a history of eating that food, there is a positive IgG.
But when a test result comes back with 10-20 foods that show positive IgG results for foods that may or may not produce intolerance, there is a good reason to question all those positive results.
Higher IgGs may relate simply to foods eaten more frequently
As some other studies have indicated, the study indicates the possibility that by eating more of a food, our immune system creates a greater tolerance to it, and thus produces higher IgG levels. This possibility exposed by the research means that higher IgG levels may actually relate to a lower intolerance to that particular food instead of a greater intolerance:
“Finally, the study does not provide an answer to the question of whether food-specific IgGs play a protective role or an allergic role in adults.”
This also explains why a particular test result can be positive for a person who has an intolerance to that particular food. If a patient reports food intolerance to a particular food or foods, this typically means they have been eating that food with at least a measure of frequency.
Other research has questioned IgG testing for food sensitivities
While this study is the largest and first of its kind to objectively test such a large population of both healthy and food-intolerant individuals, previous studies on IgG testing have concluded similar results. In a review of the data from a number of studies, the Task Force from the European Academy of Allergy and Clinical Immunology (EAACI) found:
“Testing for blood IgG4 against different foods is performed with large-scale screening for hundreds of food items by enzyme-linked immunosorbent assay-type and radioallergosorbent-type assays in young children, adolescents and adults. However, many serum samples show positive IgG4 results without corresponding clinical symptoms. These findings, combined with the lack of convincing evidence for histamine-releasing properties of IgG4 in humans, and lack of any controlled studies on the diagnostic value of IgG4 testing in food allergy, do not provide any basis for the hypothesis that food-specific IgG4 should be attributed with an effector role in food hypersensitivity.”
Other allergy associations from around the globe have stated similar findings and guidelines against utilizing IgG testing to diagnose food intolerances. These include:
- American College of Allergy, Asthma and Immunology (ACAAI)
- American Academy of Allergy, Asthma and Immunology (AAAAI)
- Australasian Society of Clinical Immunology and Allergy (ASCIA)
- Allergy Society of South Africa
- The Food Allergy Initiative.
Of course, this leaves open other possibilities related to food sensitivities – that have not been readily explored. Namely, the real causes and the ability to reverse food intolerances.
Zeng Q, Dong SY, Wu LX, Li H, Sun ZJ, Li JB, Jiang HX, Chen ZH, Wang QB, Chen WW. Variable food-specific IgG antibody levels in healthy and symptomatic Chinese adults. PLoS One. 2013;8(1):e53612. doi: 10.1371/journal.pone.0053612.
Mullin GE, Swift KM, Lipski L, Turnbull LK, Rampertab SD. Testing for food reactions: the good, the bad, and the ugly. Nutr Clin Pract. 2010 Apr;25(2):192-8. doi: 10.1177/0884533610362696.
Jenkins M, Vickers A. Unreliability of IgE/IgG4 antibody testing as a diagnostic tool in food intolerance. Clin Exp Allergy. 1998 Dec;28(12):1526-9.
Stapel SO, Asero R, Ballmer-Weber BK, Knol EF, Strobel S, Vieths S, Kleine-Tebbe J; EAACI Task Force. Testing for IgG4 against foods is not recommended as a diagnostic tool: EAACI Task Force Report. Allergy. 2008 Jul;63(7):793-6. doi: 10.1111/j.1398-9995.2008.01705.x.