Skin tests in clinical practice and epidemiology

General paediatricians and the case of resolving peanut allergy

Children with peanut allergy are almost always advised to avoid nuts for life. There have been recent reports from academic centres that in some cases the allergy might resolve and thus these dietary restrictions can be lifted. To evaluate resolution of peanut allergy in a selected group of children in a general paediatric setting. Children 4-16 yr old with a clear history of an allergic reaction to peanuts who had not had any reaction in the previous 2 yr were eligible. Specific immunoglobulin E (IgE) or skin prick test (SPT) at the time of diagnosis was sought. A SPT and specific IgE was then done and if this was <or= 8 mm and <or= 17.5 kU[A]/l respectively, a double-blind placebo-controlled food challenge was undertaken. A negative challenge consisted of tolerance to a cumulative dose of 15.8 g peanuts followed by an open challenge. From the 82 case notes reviewed 54 children were eligible to participate. Twenty-nine agreed to participate and underwent SPT (29) and specific IgE (28). Of these children eight were eligible for food challenge. Four challenges were negative and four positive. Peanut allergy may resolve in approximately 15% of selected children attending an allergy clinic run by general paediatricians in a district general hospital. Food challenge constitutes the appropriate way of removing the burden that comes with a diagnosis of peanut allergy and enables dietary restriction to cease.

Do asthma patients in general practice profit from a structured allergy evaluation and skin testing? A pilot study

BACKGROUND

Although allergy is central to the pathophysiology of asthma, little is known about the benefits of a structured approach to allergen diagnosis and management in primary care asthma patients.

OBJECTIVES

We studied effects of a structured allergen evaluation and allergen avoidance advice combined with or without additional allergy skin testing on health status, illness perception, and lung function of asthma patients treated in general practice.

METHOD

Fifty-four asthma patients were randomly assigned to three groups: (i) Standard asthma care with information on the stepwise treatment approach, a written action plan, and inhaler technique training; (ii) Additional structured allergen evaluation and avoidance advice; (iii) Additional structured allergen evaluation and avoidance advice based on skin prick test results. Patients were seen for one initial appointment at a primary care asthma clinic and a follow-up examination 3 months later. On both occasions, questionnaire measures of symptoms, illness perception, and the perceived control of asthma were administered. Lung function was measured by spirometry (PEF, FEV1). Perceived allergic asthma triggers, the trigger impact, and the trigger control were assessed in both intervention groups.

RESULTS

Following intervention, a decrease in beta-adrenergic inhaler use, an increase in the perceived control of asthma, and a decrease in the bothering from asthma symptoms were observed for all three groups. Intervention groups showed a higher awareness of animal-allergic triggers, and the perceived control of asthma triggers was increased in the group receiving no skin tests. FEV1 showed an improvement in both intervention groups.

CONCLUSION

Structured allergy evaluation and avoidance advice can improve lung function and the control of asthma in primary care. Further research is needed on the additional benefits of allergy skin testing.

[Molecular aspects and diagnostic value of fungal allergens]

Cloning, sequencing and production of highly pure recombinant allergens allows to produce perfectly standardised allergen preparations. The development of a new cloning system based on filamentous phage allowed the fast isolation and characterisation of allergens from the fungus Aspergillus fumigatus. The produced recombinant allergens were tested in serological and clinical studies as well as for their performance for routine assessments in the ImmunoCAP-system. Thereby, a perfect correlation between skin test results and serology was found showing the potential of recombinant allergens for the diagnosis of allergic diseases. Moreover, the characterisation of fungal allergens substantially contributes to our understanding of the molecular nature of proteins involved in the elicitation of allergic reactions. Apart from allergenic proteins with unknown biological function, fungal allergens can be subdivided into two classes: 1. Species-specific, secreted proteins and 2. cytoplasmic, even in phylogenetically distant organisms, well conserved proteins. These fungal allergens show extended sequence similarity, a high level of IgE cross-reactivity and in some cases also cross-reactivity with homologous human proteins indicating autoimmune reactions involved in fungal allergy.

Measuring atopy in a multi-centre epidemiological study

Skin prick tests are used as a measure of atopy in epidemiological studies, but results may be influenced by the fieldworker performing the test. In a multi-centre epidemiological study the method of reporting the results should consider the need for comparability of findings from different centres. Data on over 1000 subjects from three English centres of the European Community Respiratory Health Survey were analysed to determine whether allergen wheal should be adjusted for histamine wheal, and what cutoff diameter gave the most comparable results. No consistent relation between allergen wheal diameter and histamine wheal diameter was found for any fieldworker or allergen. A cutoff of > 0 mm for a positive result gave a more consistent relation with the corresponding specific IgE value between fieldworkers than either a cutoff of > or = 3 mm or the use of the mean wheal diameter. While this result is not immediately generalisable to studies using different skin prick test reagents, the method of analysis to determine the appropriate criterion of reporting can be used in other epidemiological studies.