More Allergy and Intolerance Testing Nonsense: Part 2
Allergy Magazine has recently published a feature on DIY Diagnosis. There is a reasonable introductory summary about the difficulties of gaining access to allergy diagnosis and management on the NHS. There is the usual sloppiness about referring to allergies and intolerance as if they are synonymous. The author uncritically reproduces a number of claims that are frequently repeated but I have yet to see substantiated:
[h]aving an allergy is now one of the most common health complaints in the UK, affecting an estimated 23 million people and four out of ten school children. Up to 40 per cent of the population are sensitive to the three most common allergens: dust mites, pollen and pets. Millions more are intolerant to certain foods, most commonly wheat and dairy.There is the usual pop quiz where the reader is told that if they have 3 or more of a 16-item list of symptoms then they might have an allergy or food intolerance. The symptoms are the usual suspects: irritable bowel syndrome; constipation; bloating; migraines; anxiety; sinusitis; joint pains; fatigue; low immunity; itchy skin, rashes and eczema; acne or dry skin; itching, swollen lips and face; coughing or wheezing; shortness of breath; dry, itchy throat; diarrhoea or vomiting. Dr. Hadler writes about the medicalization of misery and would probably like a hands-up by anyone who hasn't experienced several of those symptoms over the last year.
The writer does make a handwave towards acknowledging that
[t]here is no clinically proven test for food intolerance yet, but the IgG blood test is the only test with scientific evidence to back up its reliability. [Emphasis added.]She quotes advice from experts on what to look for in a test.
Liz Tucker, allergy nutrition expert and wellbeing consultant says, ‘Research any test well before you jump in. Some tests are very accurate and have scientific evidence to prove it. But others have no records of accuracy and no evidence to prove it works. Always go for a clinically validated test.’Liz Tucker is one of the YorkTest-styled experts who endorses YorkTest's range. According to the writer of DIY Diagnosis,
Alex Gazzola, author of Living with Food Intolerance...agrees: ‘Don’t take advice from unqualified people offering unvalidated tests on the high street. I would avoid any test that has not been validated scientifically.’Gazzola's book is available from YorkTest and endorsed by Allergy UK's Muriel Simmons. At some point, it would be very helpful if somebody other than this self-referential pool of experts were to claim that these tests are clinically or scientifically validated and provide a summary of the research to prove it.
I did have high hopes that I might see some evidence for scientific and clinical validation for allergy and intolerance testing when I read:
Imutest is a clinically proven IgE allergy test, just like those used in hospital laboratories. In a study of 200 patients referred to an NHS allergy clinic for allergy tests, Imutest correctly identified allergies present with an accuracy of 98% in comparison to the gold standard laboratory test method.I tried to consult Imutest's website but it seems that they have recently gone into receivership. I searched Entrez PubMed and could not find a reference to Imutest. I contacted the journalist but it seems as if this claim was made in the material that was sent to her by Imutest and she no longer has the background research that she did for the piece. That's unfortunate: I don't have much disagreement with a well-conducted IgE test but I would have liked to have seen the reference. At the risk of sounding like a broken record, I don't think that a test result is sufficient as a stand-alone diagnosis; a good diagnosis also depends upon a good clinical history that is interpreted by a clinician with relevant qualifications.
DIY Diagnosis refers to several YorkTest products: the YorkTest Food Intolerance Indicator, the YorkTest 42 Foodscan, the YorkTest 113 Foodscan and the Yorktest Multi-Allergy Screening Test. She writes the following about the reliability of the YorkTest tests:
All tests are highly accurate in diagnosis between 95 -97%. For the Foodscan range, 70% of those tested who followed the advice given reported an improvement in their symptoms.I have looked high and low for an authoritative source for these claims about the YorkTest tests. I can't find them. I have seen these claims so often that I have to assume that there is reputable and substantial scientific literature to back them up but I have to declare that I have so far been completely unsuccessful in finding that research.
The journalist indicates that she discriminates between reliable, authenticated tests and those of a more dubious provenance. She mentions the BEST (Bio Energetic Stress Test) system and makes this comment about its reliability:
[c]urrently there is no clinical evidence to support this method of testing.I would say that the current position of relevant professional bodies is that there is no clinical evidence to support the use of IgG testing in the diagnosis of food intolerance (more on the lack of support for IgG testing).
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