Prospective evaluation of allergen-component resolved diagnostic allergy testing and its relation to clinical features of allergic disease in children

The diagnostic possibilities in childhood allergies are rapidly changing. Only
a few years ago, sensitization to specific whole allergens was considered to be
diagnostic of allergy. More recent studies have shown that allergen
sensitization is not always accompanied by clinical reactivity to the allergen,
in particular to foods. This has been particularly well documented for peanut
sensitization in children, where the large majority of children sensitized to
whole peanut allergen do not show allergic symptoms when ingesting peanut
orally. Because of the unclear relationship between peanut sensitization and
clinical peanut allergy, prevalence rates of parent-reported food allergy in
children vary considerably between surveys. Accumulating evidence suggests that
component resolved diagnostics (CRD), i.e. testing of sensitization to specific
allergen components instead of testing sensitization to the whole allergen,
may improve the relationship between sensitization and clinical allergy in
children. For example, the sensitivity and specificity of specific
immunoglobulin E (IgE) to the peanut allergen Ara h2 to oral food challenge
outcome in children has been reported as 60% and 98%, respectively.These were
preliminary studies comparing children with and without known peanut allergy,
however. The use of CRD in other food allergies and in inhalant allergies is in
its infancy. Further studies are therefore needed to evaluate the relationship
of CRD to clinical allergy in children.
Although guidelines on the diagnosis of allergic disease in children are
available, both nationally and internationally, these documents differ
considerably, reflecting the rapidly changing possibilities and viewpoints
regarding the usefulness of allergy testing in clinical practice. For example,
whilst the 2010 revision of the Dutch general practitioners* guideline of the
diagnosis of food allergy recommends not to use specific IgE testing to foods
because of their limited ability to predict clinical food allergy, most
international practice guidelines suggest that the diagnosis of food allergy
may be reliably made based on a suggestive history, combined with evidence of
atopic sensitization to the relevant allergen. These striking differences
between guidelines are likely to leave primary and secondary care clinicians
confused as to the true role of specific IgE testing in the diagnostic work-up
of allergic diseases in clinical practice. It is likely that the improved
diagnostic accuracy of specific IgE testing by splitting up allergen responses
into responses to different allergen components will be helpful in diminishing
this confusion, but this must be supported by high-quality data from a large
and representative patient sample.

by improving the understanding of the relationship of CRD to clinical
expressions of allergic disease in children, this study aims at generating data
that can improve the development of tools that will help the primary or
secondary care practitioner to interpret results of specific IgE testing to
allergens and their components in a clinically meaningful context.

prospective cohort study

minimal burden (once only additional blood sampling of 10 ml of blood; no
additional venipuncture; once only completion of questionnaires by parents), no
risk