Monday, October 01, 2007

NHS Choices Spreads Confusion About Allergy and Intolerance Tests

Question mark and reminders
Journalists and and a certain class of nutritionists frequently conflate allergy and intolerance. UK newspapers regularly carry stories about 'food allergies' where the topic is actually food intolerance and it is not unusual for IgG blood testing to be promoted as a scientifically and clinically validated test for the diagnosis of food allergies or intolerance. These misunderstandings are so common that I notice when a journalist doesn't make these mistakes.

Nonetheless, I was particularly irritated when a correspondent drew my attention to an NHS site with a section dedicated to allergies: Which allergy test? The page carries some useful information about various tests, both those which are available from the NHS and those that are direct-to-consumer. For some of the tests (e.g., the hydrogen breath test for lactose intolerance or the coeliac self-test) there is information about the specificity and sensitivity, as reflected in the number of accurate diagnoses, false positives or false negatives. Some of the descriptions even carry a warning that some tests are "[d]ismissed by allergists as unreliable and unscientific" (systematic kinesiology) or may be offered by people who "may not have relevant qualifications" (VEGA). The inclusion of such information for some tests and not for others makes it seem as if there are no comparable concerns for those tests where they are not mentioned rather than a lack of actual clinical data or research.

However, the credulous writer/s gave no such caveats about YorkTEST’s foodSCAN tests.
In this test, you send a small blood sample to YorkTest Laboratories. The lab examines your blood for IgG antibodies, which it believes cause food intolerance. Results are given in a traffic-light code: foods to avoid (red), to rotate (amber), and to eat freely (green).
Tests for: food intolerance.
Pros: the only intolerance test supported by Allergy UK. It is also supported by well-known figures such as Dr Hilary Jones and Patrick Holford.
Cons: very expensive (around £250).
However, when the well-respected clinician, Dr Glenis Scadding, Consultant Allergist at the Royal Nose, Ear and Throat Hospital gave her testimony to a House of Lords Committee that was considering allergy and allergic disease in the UK, she characterised IgG tests for food intolerance as a waste of money":
What I do dispute is that it is worth making any attempt to identify IgG antibodies. We all make IgG antibodies to food....I see no way in which this can be used to guide diet.

I don't think there's any point in spending money on IgG antibody tests. You're better off going to see a dietitian and using an exclusion diet followed by reintroduction. The IgG antibody tests are liable to leave patients on diets that are inadequate and patients often like to think they're improving. They carry on in the teeth of very little improvement and may end up malnourished.

I think [self-testing kits] should be banned.
The YorkTest foodSCAN range is available as direct to consumer tests; however, they are also frequently recommended by nutritionists who typically do not have any recognised or specific training in allergy diagnosis or management. It isn't clear why the people who put the NHS Choices Guide together did not take note of this strong criticism from an acknowledged expert when they noted allergists' criticism for other tests but chose to mention that the foodSCAN test is endorsed by well-known names without disclosing their relationship with YorkTest. Similarly, the Allergy UK Consumer Award is only based on anecdotal report and is no indication of clinical or scientific value. Allergy UK is admonished for their support of this testing in the House of Lords report.

In a comprehensive report HL 166-I (pdf from which pg numbers are given), the Committee makes a number of good recommendations and provide some useful summaries. Pages 86-88 cover the issue of direct-to-consumer tests such as the YorkTest foodSCAN IgG test for food intolerance and the YorkTest-Allergy UK MAST IgE test for allergies to food and airborne allergens, amongst others.

The House of Lords summed up their advice as follows (pg 87):
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 urge general practitioners, pharmacists and charities not to endorse the use of these products until conclusive proof of their efficacy has been established.

It almost seems gratuitous to add that the House of Lords aligns themselves with clinical experts in their notion of who is qualified to diagnose allergies and allergic disease (hint, it is not the typical holder of a Diploma ION nor an auto-didact nor self-proclaimed expert nor celebrity nutritionists).

It is absolutely clear that the House of Lords has considered the evidence and finds that there is no adequate scientific or clinical support for the usefulness of these blood tests as a direct to consumer item; further than that, there is clear cause for concern as to the relevance of the tests. The House of Lords urges professionals in positions of responsibility and authority, whose opinions or recommendations may influence others, to refrain from endorsing this technique. NHS Choices includes cautions about other tests and techniques, it should include them about the YorkTest foodSCAN range and IgG testing for food intolerance.

People trust sources of information that come with the implicit imprimatur of the NHS. The information about the allergy tests is shoddily researched and rather confusing. NHS Choices should rethink their guide. They need to amend the text about IgG food intolerance tests and some direct to consumer allergy and intolerance tests to reflect the well-founded concerns expressed in the report from the House of Lords.

Related reading:

Science Lessons takes a lively look at kinesiology for food intolerance testing
Patrick Holford, IgG Testing and the House of Lords
Patrick Holford and His "Deeply Impressive" Scientific Proof
Patrick Holford Endorses Allergy/Intolerance Blood Test: The House of Lords Wants Responsbile Professionals To Cease Endorsement of Such Techniques
Food intolerance testing and migraine
Truthiness and referenciness make the case for IgG food intolerance tests
More allergy and intolerance testing nonsense: part 1
More allergy and intolerance testing nonsense: part 2
Quote Mining and Misrepresentation: Poor Ways to Claim Clinical Validation or Sound Science
What is the Significance of IgG Antibodies and Testing?
Why IgG Testing for Food Intolerance Is Not As Simple As ABC or Doh Ray Mi

Labels: , , , , , , , ,