Serum allergen-specific IgE reactivity: is there an association with clinical severity and airway eosinophilia in asthmatic cats?

Abstract

Objectives The aim of this study was to evaluate the results of serum allergen-specific IgE testing in cats with a clinical diagnosis of asthma and to determine if the number of allergens with positive IgE reactivity and magnitude of positive IgE responses would be associated with the severity of clinical signs or airway eosinophilia. Methods Medical records from 2008 to 2018 were retrospectively reviewed. Inclusion required a diagnosis of feline asthma based on consistent clinicopathologic features and bronchoalveolar lavage (BAL) cytology with >10% eosinophils; additionally, cats needed to have the results of serum allergen-specific IgE tests. Results Eighteen cases satisfied the inclusion criteria. Median age was 5 years and the most common presenting clinical sign was cough (n = 10/18). Most cats lived exclusively indoors (n = 13/18). The median percentage of BAL eosinophils was 47%. Serum allergen-specific IgE testing supported an underlying allergic etiology in 14/18 (78%) cats, with all but one having polysensitization. The severity of clinical signs and magnitude of airway eosinophilia did not correlate with the degree of positive IgE reactivity. Conclusions and relevance This study identified a strong association between the identification of allergen-specific IgE and cats with asthma, and the majority of these cats were polysensitized. However, larger numbers of allergens with positive IgE reactivity or magnitude of IgE reactivity were not significantly associated with clinical severity or airway eosinophilia. Knowledge of positive allergen-specific IgE results could guide allergen avoidance, regardless of the magnitude of IgE reactivity.

Serum immunoglobulin E responses to aeroallergens in cats with naturally occurring airway eosinophilia compared to unaffected control cats

“…11 Finally, a recent noncontrolled retrospective study reported intermediate and positive serum IgE responses in a majority (78%) of cats with respiratory signs related to eosinophilic airway disease. 13 We hypothesized that the number of cats with naturally occurring eosinophilic airway disease that produced allergen-specific IgE would be significantly higher than the number of control cats, which were matched for age and environment. We also hypothesized that the number of positive allergen reactions would be higher in affected as compared with control cats.…”

Immunopathogenesis of the feline atopic syndrome

“…62 A very recent retrospective study of 18 cats with a clinical diagnosis of asthma failed to show any association between the number and strength of allergen-specific IgE reactions on serology and the severity of clinical signs or airway eosinophilia. 63 The authors nonetheless concluded that there was a strong association between the identification of allergen-specific IgE in that 14 of the 18 cats (78%) showed positive reactivity. However, the absence of a control group raises questions as to the validity of this conclusion.…”

“…However, the absence of a control group raises questions as to the validity of this conclusion. 63 In the first and only study on the efficacy of ASIT for spontaneous feline asthma, IDT was performed on 20 cats that fulfilled the necessary clinicopathological diagnostic criteria. 64 Positive results were seen in 15 cats, mostly to HDMs and to a lesser extent, to pollens.…”

“…The 10 cats without skin disease selected had a significantly greater incidence of positive IDT reactions and positive allergen‐specific IgE serology than did an age‐matched control group 62 . A very recent retrospective study of 18 cats with a clinical diagnosis of asthma failed to show any association between the number and strength of allergen‐specific IgE reactions on serology and the severity of clinical signs or airway eosinophilia 63 . The authors nonetheless concluded that there was a strong association between the identification of allergen‐specific IgE in that 14 of the 18 cats (78%) showed positive reactivity.…”

“…The authors nonetheless concluded that there was a strong association between the identification of allergen‐specific IgE in that 14 of the 18 cats (78%) showed positive reactivity. However, the absence of a control group raises questions as to the validity of this conclusion 63 …”