The Clinical Utility of Recombinant Component Testing for Nut Allergy in Doha, Qatar

Abstract

Prior studies found high prevalence of respiratory diseases in IgE-deficient patients (IgE<2.5 kU/L). The utility of allergen-specific testing in these patients is unknown. We investigated skin and serum specific IgE (ssIgE) test positivity to environmental allergens in patients with IgE-deficiency. METHODS: IgE-deficient patients with rhinitis and/or asthma diagnoses who had skin prick testing (SPT), intradermal skin testing (IDST) and/or ssIgE done (2010-2018) were randomly matched (age and gender) to three groups of patients with rhinitis and/or asthma who had environmental testing during the same period: normal IgE (2.5≤IgE<100), high IgE (100≤IgE<1000), very high IgE levels (≥1000 kU/L). RESULTS: Out of 71 IgE-deficient patients identified, 21 (30%) had at least one positive skin test, compared with 69% of patients with normal (p<0.05), 94% with high (p<0.05) and 93% (p<0.05) with very high IgE levels. In IgE-deficient individuals, SPT identified at least one sensitization in 14/71 (20%) patients (mean of 364 positive SPT/patient), IDST in 11/37 (15.5%) patients and ssIgE were positive (ssIgE>0.1 kU/L) in 2/52 (3.8%) individuals. The proportion of patients being on subcutaneous immunotherapy (IT) was 4.2% in the IgE-deficiency group, similar with the rate of IT in individuals with normal IgE levels (5.6%, p50.7) and significantly lower than in those with high (19.7%, p<0.01) and very high IgE levels (22.9%, p<0.01). CONCLUSIONS: Although IgE-deficient patients lack serum IgE, about a third of those with respiratory symptoms have positive skin testing. Allergen-specific tests are useful to diagnose environmental sensitizations and prescribe immunotherapy in IgE-deficient individuals.