Compromising between European and US allergen immunotherapy schools: Discussions from GUIMIT, the Mexican immunotherapy guidelines

Background

Allergen immunotherapy (AIT) has a longstanding history and still remains the only disease-changing treatment for allergic rhinitis and asthma. Over the years 2 different schools have developed their strategies: the United States (US) and the European. Allergen extracts available in these regions are adapted to local practice. In other parts of the world, extracts from both regions and local ones are commercialized, as in Mexico. Here, local experts developed a national AIT guideline (GUIMIT 2019) searching for compromises between both schools.

Methods

Using ADAPTE methodology for transculturizing guidelines and AGREE-II for evaluating guideline quality, GUIMIT selected 3 high-quality Main Reference Guidelines (MRGs): the European Academy of Allergy, Asthma and Immunology (EAACI) guideines, the S2k guideline of various German-speaking medical societies (2014), and the US Practice Parameters on Allergen Immunotherapy 2011. We formulated clinical questions and based responses on the fused evidence available in the MRGs, combined with local possibilities, patient's preference, and costs. We came across several issues on which the MRGs disagreed. These are presented here along with arguments of GUIMIT members to resolve them. GUIMIT (for a complete English version, Supplementary data) concluded the following.

Results

Related to the diagnosis of IgE-mediated respiratory allergy, apart from skin prick testing complementary tests (challenges, in vitro testing and molecular such as species-specific allergens) might be useful in selected cases to inform AIT composition. AIT is indicated in allergic rhinitis and suggested in allergic asthma (once controlled) and IgE-mediated atopic dermatitis. Concerning the correct subcutaneous AIT dose for compounding vials according to the US school: dosing tables and formula are given; up to 4 non-related allergens can be mixed, refraining from mixing high with low protease extracts. When using European extracts: the manufacturer's indications should be followed; in multi-allergic patients 2 simultaneous injections can be given (100% consensus); mixing is discouraged. In Mexico only allergoid tablets are available; based on doses used in all sublingual immunotherapy (SLIT) publications referenced in MRGs, GUIMIT suggests a probable effective dose related to subcutaneous immunotherapy (SCIT) might be: 50-200% of the monthly SCIT dose given daily, maximum mixing 4 allergens. Also, a table with practical suggestions on non-evidence-existing issues, developed with a simplified Delphi method, is added. Finally, dissemination and implementation of guidelines is briefly discussed, explaining how we used online tools for this in Mexico.

Conclusions

Countries where European and American AIT extracts are available should adjust AIT according to which school is followed.

[Allergy to egg proteins in children]

Food allergy prevalence has increased during the last years, affecting 15-20% of children, in this case, egg allergy affects from 0.5-2.5%. Most of the egg allergic reactions are type I or IgE mediated antibodies against egg proteins. Five major proteins have been identified: ovomucoid (Gal d1), ovoalbumin (Gal d2), ovotransferrin (Gal d3), lysozyme (Gal d4) and albumin (Gal d5). Ovomucoid protein, which is found in the egg white, is heat resistant and enzyme resistant. This protein is the most allergenic and the most common in egg composition. Clinical diagnosis requires a detailed questionnaire. Skin prick test or Ige specific diagnosis are made as first choice. Skin prick tests are quick and useful to determine the presence of IgE specific antibodies to egg. Specific IgE for egg can be measured using standarized IgE studies in vitro, making a quantitative measure. Traditionally with the clinical history a diagnosis can be made. Standarized oral double blinded-placebo controlled challenge continues to be the gold standard for food allergy diagnosis. The identification and elimination of egg proteins from the diet is the primary treatment and the only one validated to this food, but there are more studies needed to stablish protocols for each specific egg allergen before the oral inmunotherapy becomes a routine practice.

Alergia a las proteínas del huevo en edad pediátrica

La prevalencia de alergia alimentaria se incrementó en los últimos años: afecta de 15 a 20% de la población infantil; específicamente, la alergia al huevo afecta de 0.5 a 2% de población pediátrica. La mayor parte de las reacciones alérgicas al huevo son tipo I; es decir, son mediadas por anticuerpos de tipo IgE dirigidos contra proteínas contenidas en este alimento. Se ha identificado cinco alergenos mayores: ovomucoide (Gal d1), ovoalbúmina (Gal d2), ovotransferrina (Gal d3), lisozima (Gal d4) y albúmina (Gal d5). La mayor concentración de proteínas alergénicas están en la clara del huevo (Gal d1-4), mientras que en la yema de huevo sólo encontramos una (Gal d5). La proteína ovomucoide, que contiene la clara, es resistente al calor y a las enzimas digestivas; se considera la proteína con mayor poder alergénico y la ovoalbúmina es la proteína más abundante. El diagnóstico clínico requiere una detallada anamnesis. Por lo general, se realiza cualquiera de las pruebas (cutáneas o IgE específica) como primera opción. Las pruebas cutáneas son una prueba rápida y útil para determinar la existencia de anticuerpos IgE específicos al huevo. La IgE específica al huevo puede medirse cuantitativamente mediante estudios estandarizados de IgE in vitro. En conjunto con una buena historia clínica, se utilizan para apoyar el diagnóstico clínico. El reto oral estandarizado, doble ciego, controlado con placebo, aún es el patrón de referencia para el diagnóstico de alergia alimentaria. La identificación y eliminación en la dieta de la proteína de huevo responsable de las reacciones alérgicas es el tratamiento primario y el único validado contra la alergia a este alimento, pero se necesitan más estudios para establecer los protocolos para cada alergeno específico del huevo, antes de que la inmunoterapia oral se convierta en una práctica rutinaria.