Times gets it right on food allergy tests… mostly

admin February 25, 2010 1 Comment

Testing for food hypersensitivities is a confusing business. Here’s a summary of what the medical profession can do:

1. Coeliac disease can be tested for effectively through a number of blood tests and a biopsy.
2. Food allergies can be diagnosed clinically using a combination of several of the following: blood testing, skin prick testing, challenge testing and examining clinical histories.
3. Of the food intolerances, only lactose intolerance can be tested for – by using the hydrogen breath test.

Set those three aside, and we’re entering controversial territory. There are no tests for other possible intolerances which are accepted by orthodox medicine. The only way to reliably diagnose them is through an elimination and reintroduction diet, under the close supervision of a specialist dietitian.

As most people are aware, there are other tests available privately whose manufacturers maintain can help identify intolerances, and there are many alternative therapists who claim to be able to diagnose food sensitivities using their unproven techniques.

This Times story this week does a reasonable job of warning the reader about many of them.

My key quibble is that the article, like many before it, uses the slightly unsatisfactory tactic of recruiting a non-food-allergic journalist to discredit procedures which claim to test for food intolerances and not classical food allergies. And besides, we all know one example isn’t enough to prove or disprove – even the widely accepted food sensitivity tests I mentioned above can produce false positives too.

But the key matter is whether these tests work or not. Is there a body of evidence supporting them, based on randomised double-blind placebo controlled trials, published in peer-reviewed medical journals?

No.

The exception is IgG testing, for which there is one trial, which was mildly positive. IgG testing is offered by two organisations – YorkTest and Cambridge Nutritional Sciences. Despite the endorsement of Allergy UK and, in the former case at least, of some well-known individuals, these tests are not considered suitable for diagnosing food intolerances by most independent experts working in the field, who believe the theory on which they are based – that raised IgG antibodies indicate possible food intolerances – is at present unproven. Vigorous (and ongoing) PR has seen both get some positive coverage (including, I’m afraid, in the past, from me) and some high-profile “it worked for me’s”, but the case for IgG testing has been dealt a severe blow by people brighter than yours truly elsewhere on the web, and I certainly can’t improve on it here. If you’re interested, this is a fairly good place to start, but I’ll post up others when I find them.

As far as Mr Joe Public is concerned, I feel he needs to ask himself who to believe.

Does he believe people such as kinesiologists, most of whom have no medical training, and who think they can diagnose food sensitivities by placing foods on people’s bellies and checking their physical strengths?

Does he believe people who are trying to sell him very expensive tests?

Or does he believe independent medical professionals with no vested interests?

I hope it’s the last of the three. Because the people who really matter – that’s allergists, immunologists, gastroenterologists and dietitians – with very few exceptions do not accept these tests. And although sometimes these experts may be unsympathetic to people experiencing chronic problems – as my last post concerning Dr Max Pemberton’s article in the Telegraph exemplified – it doesn’t make the alternative any wiser an option, at present.