A comparison of intradermal testing and detection of allergen-specific immunoglobulin E in serum by enzyme-linked immunosorbent assay in horses affected with skin hypersensitivity.

This study aimed to develop and test a new method for diagnosing skin allergies in horses, using an allergen-specific enzyme-linked immunosorbent assay (ELISA), a diagnostic tool used in clinical immunology, and compared its efficacy to the more established intradermal testing.

Objective and Methodology

• The researchers were interested in improving the method for diagnosing skin allergies in horses. Skin hypersensitivities in horses are often diagnosed only based on clinical signs, without further testing to confirm the allergic nature of the disease or to identify the specific allergens involved.
• The study aimed to develop an allergen-specific ELISA using a monoclonal antibody tailored for horse immunoglobulin E (IgE), an antibody that plays a crucial role in allergies.
• The newly developed ELISA was used to examine the potential for detecting allergens in serum and was compared to the traditional intradermal testing.
• The research team performed intradermal testing with 61 allergen extracts on ten horses known to have skin hypersensitivity. The same horses had their blood serum analyzed using the ELISA for antibodies to the same allergens.

Results

• The concordance between the ELISA results and the intradermal test results was evaluated using the kappa test. This test is used for comparing the agreement of two methods. Only two of the 61 allergen extracts (Timothy and Quack) showed substantial agreement, with kappa values greater than 0.60.
• The statistical comparison of the remaining 59 allergens showed little or no agreement between the two tests beyond what could be expected by chance alone. This suggests that the ELISA’s performance in detecting allergens in horses’ serum did not match the results from intradermal testing for the majority of the allergens.

Further Analysis and Conclusion

• To explore potential factors that might have influenced the ELISA’s sensitivity, the researchers modified the assay to detect other types of immunoglobulins in the serum, specifically IgGb and IgG(T), and also determined the protein content in all tested allergen extracts.
• They found high variations in detectable protein content among the commercial allergen extracts, which might have affected the ELISA’s performance. Additionally, high concentrations of allergen-specific IgG in horse serum were found to compete with IgE for binding to the plates used in the ELISA, potentially reducing the test’s sensitivity to IgE.
• The findings suggest that, when using whole serum and crude allergen preparations, the ELISA may provide limited diagnostic information in horses.
• The study emphasizes the importance of reliable diagnosis of allergens in equine skin hypersensitivity, as this can help shape specific treatments for allergic reactions or the development of allergy vaccines in horses.