Comparison of immediate intradermal test reactivity with serum IgE quantitation by use of a radioallergosorbent test and two ELISA in horses with and without atopy

OBJECTIVE

To compare a radioallergosorbent test and 2 ELISA with intradermal testing for the determination of environmental allergen hypersensitivity in horses with and without atopic diseases.

DESIGN

Prospective clinical study.

ANIMALS

10 horses with recurrent urticaria, 7 with atopic dermatitis, 16 with chronic obstructive pulmonary disease, and 22 without atopy.

PROCEDURE

History, physical examination, hemogram, serum biochemical analyses, bronchoalveolar lavage, and an intradermal test (used as the criterion standard) with a regional panel of 73 allergens were performed in all horses. Serum was analyzed by use of the 3 in vitro assays of allergen-specific IgE.

RESULTS

An ELISA based on the alpha chain of the high-affinity IgE receptor, the Fcepsilon receptor immunoglobin epsilon chain (FcepsilonRIalpha) for IgE, had the overall highest kappa statistic (0.238), positive predictive value (49%), and negative predictive value (78%). Overall agreement between the FcepsilonRIalpha-based ELISA and the intradermal test was fair. The highest kappa statistic was obtained by the FcepsilonRIalpha-based ELISA in horses with atopic dermatitis (0.330). Kappa statistics for the radioallergosorbent test and a polyclonal antibody-based ELISA agreed slightly with that of the intradermal test at best.

CONCLUSIONS AND CLINICAL RELEVANCE

None of the 3 serum allergy tests reliably detected allergen hypersensitivity, compared with the intradermal test. The FcepsilonRIalpha-based ELISA performed significantly better overall than the other 2 tests. Low sensitivity of all 3 assays indicates the need for continued study to elucidate a more sensitive test for the determination of potentially pathogenic allergens in horses.

Comparison of response to immunotherapy by intradermal skin test and antigen-specific IgE in canine atopy

The intradermal skin test (IDST) and serologic allergy test (SAT) has been developed for confirming a diagnosis of canine atopy and determining allergens for immunotherapy. To determine the prevalence of causative allergens for canine atopic dermatitis in Japan, IDST and SAT were performed with the CMG Immunodot strips on 95 atopic dogs using 9 allergens. In addition, we compared agreement rate, sensitivity and specificity between them (using IDST as the standard). The allergen most commonly positive in both tests was house dust mites (IDST: 69.5%, SAT: 48.4%). Moreover, Japanese cedar, mugwort and grass mix were detected as attendant causative allergens. Agreement rates between the two tests ranged from 67.4% to 96.8%; the overall mean agreement rate were 81%. SAT was shown to have sensitivity to IDST ranging from 16.7 to 68.2%. The specificities were very high for all allergens, on the order of 94.9-100% (median=98.7%). Finally, the efficacy of immunotherapy was evaluated on 27 atopic dogs based on IDST (15 dogs) and SAT (12 dogs) results. Overall, 60% (9/15) of the IDST group and 66.8% (8/12) of the SAT group experienced a 50% to 100% reduction in their symptomatology. No significant differences were found in response to immunotherapy during the follow-up period between allergen selection methods. These results indicate the value of serologic tests as an aid to identifying an allergen solution for immunotherapy.

Efficacy of hyposensitization in feline allergic diseases based upon results of in vitro testing for allergen-specific immunoglobulin E

A survey was undertaken to evaluate the responses to hyposensitization in cats for which a diagnosis of allergic disease was made by assessment of clinical signs and evaluation of allergen-specific immunoglobulin E (IgE) using the radioallergosorbent test (RAST). Eighty-one cases were available for analysis. In 39 cases, a dietary change resulted in some subjective improvement, which usually was minimal; however, some cases had significant improvement. In 75.3% of cases, an improvement of at least 50% was noted and ascribed to a combination of immunotherapy and dietary change, when implemented. The response of the 42 cases in which immunotherapy alone was used or where there was no response to dietary change was broadly similar. Response of the specific dermatological conditions ranged from 93.6% in the case of linear granuloma to 60% in cases where self-induced hair loss was evident. Response also was good in cases of presumed allergic asthma (86.1% improvement) and suspected allergic otitis externa (62.6% improvement). In nine patients, the hyposensitization was discontinued due to lack of response. The results suggest that confirmation of a suspected diagnosis of allergic disease in cats by means of in vitro tests and subsequent therapy with hyposensitization should be a major consideration in feline practice.

[Atopic dermatitis in dogs. Symptomatology and diagnosis]

The immunological backgrounds of canine atopy, and in particular of atopic dermatitis, are described in the present review. The significance of the history, the intradermal allergic test and the determination of allergen-specific antibodies in the diagnosis of canine atopy are discussed.