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Food challenge tests
  1. S Roberts
  1. Wythenshawe Hospital, Southmoor Road, Manchester M23 9LT, UK; stephen.robertssmuht.nwest.nhs.uk

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Ewan and Clark’s helpful commentary provokes further comment on the diagnosis of allergy and the management of the allergic child.1 The issues raised are controversial because differences in clinical practice exist between countries, between allergy centres in the UK, and between allergists and general paediatricians. Unavailability of skin prick testing outside allergy centres accounts for some of the differences, but neither SPT or RAST distinguish between sensitisation and clinical allergy; scepticism about the meaningfulness of test results will continue until they are validated by oral food challenge (OFC) and correlated with a careful clinical history. Persistence of positive SPT is not always evidence for persistence of allergy2 and restriction of the OFC to the role of confirming resolution of allergy as suggested by Ewan and Clark will tend to disadvantage patients with indeterminate skin prick results, those with newer food allergies such as kiwi and sesame with uncertain prognosis, and those where the history is open to question. The usefulness of OFC as a tool for exploring allergic thresholds and for defining the characteristics of an individual’s allergic reaction has not yet been clearly defined but merits further study. Although OFC should only be recommended and performed by allergists experienced in the selection of appropriate patients, challenge need not be restricted by risks of severe adverse reactions, the incidence of which is reported to be approximately 1% for open challenges in routine clinical practice.3 Higher rates of severe reactions have been described in studies where larger and cumulative doses of allergen were used in double blind placebo controlled challenges.4 My own series of patients with higher rates of reactions requiring bronchodilator treatment included a high proportion of asthmatic children and they also received larger doses of allergen.5

Establishing the true presence of food allergy is fundamental to clinical management. Allergists are better at making a correct diagnosis than the non-specialist, but the various diagnostic errors and pitfalls suggest that we should be utilising all the available tests more fully in the best interests of the patient. I agree with Ewan and Clark that many more trained paediatric allergists will be required to provide this service.

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