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This Month"s Feature Review:
Immunotherapy (Desensitisation): An Update
Immunotherapy has been adopted as the best term to denote the slow immunizing process of injecting allergenic extracts in ascending doses, which causes increased tolerance to develop to the injected substance. It has come a long way since first used in 1911 by Noon, an English doctor.
Several randomised studies have shown that it is a very effective and safe treatment for allergic rhinitis, allergic asthma and anaphylaxis to insect venom.
Immunotherapy has been reported by Timothy Sullivan, MD, from Emory University Atlanta, to be "considerably less expensive than pharmacological treatment for asthma and allergic rhinitis", based on a comparative economic analysis.
The annual cost of pharmacotherapy for moderate to severe asthma was estimated at $1,000 per year, and for allergic rhinitis, approximately $1,200. Allergen immunotherapy is estimated at $800 for the initial year and $170 to $290 for each subsequent year of maintenance therapy (depending on the number of antigens involved)
This article adopts some of the summary statements from the draft manuscript Allergen Immunotherapy: A Practice Parameter&
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Improved screening for peanut allergy by the combined use of skin prick tests and specific IgE assays
Fabienne Rance, MD et al, Toulouse, France
Background: The diagnosis of peanut allergy must be based on reliable, safe, criteria. Double-blind, placebo-controlled food challenges (DBPCFCs) are the gold standard but are costly and dangerous because they can trigger severe reactions.
Objective: The aim of this study was to develop a strategy for diagnosing peanut allergy while reducing the need for DBPCFCs.
Methods: We studied 363 children referred for an evaluation of suspected food hypersensitivity. They all benefited from the same diagnostic strategy, which included, in order, clinical history, a skin prick test (SPT), and a specific IgE assay.
Personnel who were unaware of the results of the other tests performed DBPCFCs on all the children. To assess the performance characteristics of the SPT (comparing commercial and raw peanut extracts) and the specific IgE assay, we compared the results with those provided by the DBPCFCs. For SPTs and specific IgE assays, we sought to determine the cut-off values required to exclude false-positive and false-negative results.
Results: According to DBPCFC results, 177 children were allergic to peanut, and 186 were not. The performance characteristics of the SPTs were superior with the raw extract because the negative predictive value was 100% (95% confidence interval [CI], 97.5-100). If the skin reaction with the raw extract was less than 3mm, we could be quite certain that the child was not allergic. On the other hand, if the SPT resulted in a wheal diameter of larger than 3mm, we could only be 74% certain that the children were allergic. Furthermore, if the SPT resulted in a wheal diameter of 16mm or larger, we could be quite certain that the child was allergic because the positive predictive value was 100% (95% CI, 87.2-100). The combined use of the tests resulting in a positive diagnosis if the SPT result was 16mm or larger or specific IgE concentrations of 57kUA/L or greater, and in a negative diagnosis if the SPT result was less than 3mm and the specific IgE concentration was less than 57kUA/L, allowed us to classify subjects with almost complete certainty as being allergic or not because the predictive values were 100%.
Conclusion: Commercial extracts could not be used to reliably predict tolerance of peanut. Peanut DBPCFCs can be avoided when SPTs with raw extracts resulted in wheals with the largest diameter of less than 3mm and a specific IgE concentration of less than 57KUA/L and also when wheal diameters were 16mm or larger or specific IgE values were 57KUA/L or greater. Otherwise DBPCFCs were indispensable for the unequivocal diagnosis of peanut allergy.
Reference: J Allergy Clin Immunol 2002; 109:1027-33
Effects of laundry detergents on Dermatophagoides farinae (house dust mite 2), Dermatophagoides pteronyssinus (dust mite 1), and Euroglyphus maynei.
DiAnn L. et al
Background: House-dust mites in clothing and bedding are the source of major allergens. Based on studies of Dermatophagoides pteronyssinus only, weekly washing in hot water is recommended to kill dust mites and remove allergens from clothing and bedding. However, in the USA, washing is most often done in warm or cold water, and other mite species are involved.
Objective: The purpose of this study was to investigate the lethal effects of various temperatures of hot water alone and hot, warm, and cold water containing detergents and chlorine bleach on D. farinae, D. Pteronyssinus, and E. maynei.
Methods: Mites were soaked in test solutions at various temperatures and for various length of time, allowed time to recover, and then analysed for survival.
Results: D. farinae was the most temperature-sensitive and chlorine bleach-sensitive of the three species. In 50? C water alone, 100% mortality for D. farinae was obtained in 10 minutes, whereas most D. pteronyssinus and E. maynei survived. However, 53? C-soaks for 12 and 5 minutes were needed to kill all D. pteronyssinus and E. maynei, respectively. Laundry detergents at their recommended and doubled concentrations and chlorine bleach generally increased mite mortalities over water alone for the three species. Soaking for 4 hours in warm water containing various detergents alone induced mortalities of 19 to 50%, 2 to 35%, and 14 to 46% for D. farinae, D. pteronyssinus, and E. maynei, respectively.
Conclusions: Washing bed linen weekly in warm water with a 4-hour pre-soak containing most detergents and bleach will kill most D. farinae and, depending on the detergent brand, moderate numbers of D. pteronyssinus. Four-hour soaks in warm water containing the recommended concentrations of various detergents alone, also kills moderate numbers of D. farinae, D. pteronyssinus, and E. maynei. Therefore, the cumulative effect of weekly washing with long pre-soaks should significantly reduce mite levels over time in bed linens, particularly when mattresses and pillows are encased to prevent reinfestation.
Reference: Annals of Allergy, Asthma, & Immunology 2002;88:578-583
Recognition of pathogenically relevant house dust mite hypersensitivity in adults with atopic dermatitis: A new approach?
Dev Shah, et al, Leicester, UK
Background: The pathogenic importance of the ubiquitous house dust mite, D. pteronyssinus (Dp), in atopic dermatitis is unclear.
Objective: We aimed to explore the relevance of Dp hypersensitivity in adult patients with atopic dermatitis by using an invivo topical challenge method and in vitro assays for T-cell reactivity.
Methods: Dp and control skin prick test solutions were applied to the cubital fossae of 20 patients twice daily for four days; the severity of dermatitis and pruritus in the challenge sites were determined before and after testing. The same solutions were used in PMBC proliferation assays that include 10% fresh autologous serum; the latter aimed at maximizing IgE-facilitated allergen presentation.
Results: Although most patients had markedly elevated Dp-specific serum IgE levels, only 6 of 20 patients developed increased cubital fossae dermatitis severity and pruritus scores that were greater at sites of application of Dp solution than at control sites. In addition PMBC proliferations in response to Dp solution in the presence of autologous serum was significantly greater in the in vivo challenge-positive patients than in those who did not respond to challenge. A sub-group of patients (7/20) also developed transient but pronounced contact urticaria at sites of Dp application.
Conclusion: These findings suggest that hypersensitivity to Dp might be clinically relevant in approximately one third of the adult atopic dermatitis population studied. They also point to methods of identifying patients who might respond to house dust avoidance measures.
Reference: J Allergy Clin Immunol 2002; 109: 1012-8
Interpretation of commercial food ingredient labels by parents of food-allergic children
Preeti Joshi, Scott Sichererm MD et al, Mt Siani School of Medicine, New York
Background: To avoid allergic reactions, food-allergic consumers depend on the ingredient labels of commercial products. Complex ingredient terminology (eg, casein and whey for milk) and label ambiguities (eg, natural flavour and may contain peanut) might compromise the ability of patients/parents to determine the safety of particular products.
Objective: The purpose of this investigation was to determine the accuracy of label reading among parents of food-allergic children.
Methods: Parents of children on restricted diets attending our referral center were asked to review a group of 23 food labels taken from widely available commercial products. For each label, each parent/patient pair was asked to indicate wether the product was safe for the allergic child and, if it was not, which foods restricted from the childs diet were in the product.
Results: There were 91 participants. Peanut was the most commonly restricted food (82 children), followed by milk, egg, soy, and wheat (60, 45, 27 and 16 children, respectively). Identification of milk and soy was the most problematic: only 4 (7%) of the 60 parents correctly identified all 14 labels that indicated milk, and only 6 (22%) of 27 parents correctly identified soy protein in 7 products. Peanut was correctly identified in 5 products by44 (54%) of the 82 parents restricting peanut. Wheat (10 labels) and egg (7 labels) were correctly identified by most parents (14/16 and 42/45, respectively). Correct label identification was associated with prior instruction by a dietitian.
Conclusions: With current labelling practises, most parents are unable to identify common allergenic food ingredients. These results strongly support the need for improved food labelling with plainEnglish terminology and allergen warnings as well as the need for diligent education of patients about reading labels.
Reference: J Allergy Clin Immunol 2002; 109:1019-21
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