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Friday, May 14, 2010

Systematic review of food allergy papers highlights need for better studies

Public awareness of food allergy is high, which can be attributed, in part, to the work of advocacy groups. Still, in this setting, clinicians are being frustrated by the lack of reliable diagnostic and management guidelines as the demand for evaluation and intervention grows.

An article in the Journal of the American Medical Association (JAMA), published May 12th, reports rather equivocal results of a systematic literature review of food allergy. Chafen et al. (JAMA 2010, 303:1848-1856) find that there are reasons allergists are struggling to address food allergy; that’s because what is known about food allergy is of limited quality, contradictory, and lacks definitional consistency. Over 12,000 citations were reviewed for the authors’ inclusion criteria, with only 72 making the cut. The authors include prospective research in well-defined, appropriately sized populations employing oral food challenge as the diagnostic standard. Cow’s milk, hen’s egg, peanut, tree nut, fish, and shellfish were the foods represented in the 72 citations. They found that the single most confounding factor in establishing prevalence, optimal management guidelines, and prevention is the lack of a consensus diagnosis. The authors determine that self-report bias and low-quality study design, in addition to variability in diagnostic modality, make it almost impossible to develop useful practice guidelines.

Among several key points reported in the article are: 1) food allergy prevalence is greater than 1-2% but less than 10%, 2) among available tests, i.e., food challenge, food-specific IgE, and skin prick testing, not one is sufficiently easy, sensitive, or specific for recommending over the others, and 3) elimination diets are the empirical therapy, but are not supported by critical research. Of particular concern is the real possibility of over-diagnosing food allergy and exposing individuals to the medical and social stressors associated with it. The authors conclude that diagnostic criteria for food allergy are hampering the development of evidence to support clinical management.

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