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IgG Food Allergy Testing

 
It seems like everyone has a gluten intolerance these days, and I am no exception. I stopped eating gluten in 2007 because my doctor thought that gluten intolerance could be the cause of some skin issues I was having. I took it out of my diet, and it didn’t help the skin issues, but when I tried to put it back into my diet, I started having stomach pain. I had never had stomach issues before that. For the next couple of years, I oscillated between a gluten-free diet and periods of trying to reintroduce gluten. It never worked, and eventually I resigned myself to the gluten-free diet.
I asked my doctor about being tested for gluten intolerance, and she said that I had already done the most effective method of diagnosis – an elimination diet. She mentioned IgG blood tests of food intolerance, but she said that she considered them extremely unreliable. The other option involved me putting gluten back into my diet. At that point, I knew how I felt when eating gluten, so we agreed that it wasn’t worth the discomfort.
When I moved to Colorado and got a new doctor, she thought that I should be tested for food allergies. She wanted me to do the IgG blood test. I told her that my previous doctor was skeptical of the results, but this doctor insisted that the results from her lab are quite reliable. The test was covered by my insurance, so I did it. My results had a few foods that I should avoid completely and a few foods that I could eat no more than every 4 days, including gluten. Most of the other foods on the list were things that I eat regularly and had eaten within the 24 hours before the test. I tried the diet for a few weeks, but it was really challenging, and I didn’t notice any difference in how I felt, so I went back to my gluten-free diet.
After learning a bit more about allergies and immunoglobulin in class, I thought it would be interesting to look into the IgG blood testing more. The tests use ELISA method to evaluate IgG-mediated immune responses to various foods.
I found this blog post by a pharmacist who comes out pretty strongly against the tests. He evaluates the tests based on analytic validity, clinical validity, clinical utility and ethical / legal/ social implications, and concludes that the tests are a waste of money at best. He emphasizes that IgG antibodies signify exposure to foods not intolerance. Some research actually suggests that IgG might be a marker for food tolerance or resolution of food intolerance. He lists the recommendations against IgG blood testing by numerous US and European allergy associations.
Sheryl Miller, the clinical director at Bastyr University in Seattle, a school of Naturopathic medicine, wrote a review back in 1998 about the reliability of IgG blood testing. At their clinic, they sent the same blood sample to 3 labs for the tests under 6 different names – 3 of the samples were sent immediately after the blood draw and the rest were sent a week later, frozen according to guidelines. The results were not consistent. Bastyr concluded that the variability in results was unacceptable at two of the three labs. Miller also questioned the theory behind IgG food allergy testing. This paper was written many years ago, and perhaps the tests are more consistent now, but I did find more recent, similar anecdotes online.
Is there any evidence for the reliability or utility of these tests? It seems like most of the proponents are the labs themselves. I did see one clinical trial in which IBS patients who followed a diet based on IgG test results had significantly fewer symptoms than control patients. However, the study has been criticized for numerous shortcomings, including the fact that most patients on the IgG diet removed dairy or wheat, and regardless of IgG status, most IBS benefit from removing these foods.
After reading through all this information, though, I am still a little confused about whether IgG antibodies to commonly eaten foods are normal among people with no issues with leaky gut. It seems to me that food should stay in the digestive system and not be floating around stimulating an immune response, right? Are positive results on an IgG food intolerance test indicative of intestinal permeability rather than intolerance to specific foods?
References

Atkinson, W., Sheldon, T. A., Shaath, N. & Whorwell, P. J. Food elimination based on IgG antibodies in irritable bowel syndrome: a randomised controlled trial. Gut 53, 1459–1464 (2004).

Gavura, S. “IgG Food Intolerance Tests: What does the science say?” (2012).

Hunter, J. O. Food elimination in IBS: the case for IgG testing remains doubtful. Gut 54, 1203–1203 (2005).

Jones, S. M. et al. Clinical efficacy and immune regulation with peanut oral immunotherapy. Journal of Allergy and Clinical Immunology 124, 292–300 (2009).

Miller, S. IgG Food Allergy Testing by ELISA/EIA: What Do They Really Tell Us? Townsend Letter January, 62-65 (1998).

Tomičić, S. et al. High levels of IgG4 antibodies to foods during infancy are associated with tolerance to corresponding foods later in life. Pediatric Allergy and Immunology 5(1), 35-41 (2008).