Heska AG
IgE anti plant glycoproteins in pet samples.
Effect on IgE in vitro testing.
Basis
We have observed that a significant percentage of dogs with allergic disease test IgE positive for many, and in some cases all, of the plant pollens in our test panels. We have shown that IgE from this subset of dogs is binding to carbohydrate allergens that are shared in common by these pollens. We believe that the anti-carbohydrate IgE produced against the shared carbohydrates is not relevant to the clinical disease, and that the large number of positive reactions reported complicates the selection of proper allergens to include in immunotherapy prescriptions.
We have developed a new test to confirm IgE reactivity to the shared carbohydrates when it occurs, and can now modify our existing ALLERCEPT test to block this reactivity. The new tests simplify and improve the process of selecting allergens for inclusion in immunotherapy prescriptions by selectively eliminating the carbohydrate-reactive IgE from the sample before testing. In the modified test, pollen positives now indicate IgE reactivity with allergens that are more likely implicated in clinical disease.
Anti-plant carbohydrate IgE antibodies affect IgE testing
The illustration below shows the problem.
Thesesituations will lead to a specific IgE reaction which is not clinically relevant. The result of the IgE test cannot be interpreted.
Is it possible to get a positive anti pollen IgE response in samples that possess IgE to the shared CHO?
Yes. An specific assay has been developed to prevent binding of the anti-CHO IgE to the allergens tested.
The use of this blocking reagent provides:
- A positive IgE test when there is IgE reactive with the unshared (unique) pollen allergens.
- A negative test when IgE is directed only against the shared CHO.
When the presence of cross-reactive IgE against carbohydrates should ideally be assessed?
The cross-reactive IgE should be identified before an allergen panel test is performed.
The principle of the new Heska pollen CHO test
•IgE detecting system: Fc-epsilon receptor
•Allergen: Proprietary CHO allergen extract.
•Species: dog, cat and horse
CHO-test performance
On a trial performed on 500 cases from all over Europe:
•Prevalence: 150 cases; 30%
•Sensitivity: > 88%
•Specificity: > 94%
What to do when the presence of cross-reactive IgE against carbohydrates is confirmed?
The ALLERCEPT testing laboratory will run a modified ALLERCEPT test which will block the IgE reaction against carbohydrates. Three scenarios are then possible:
- When the serumwill contain IgE reactive only with the shared CHO. When this occurs, the modified test will be negative for the pollens.
- When the serum will contain IgE reactive with both the shared CHO and also other relevant (unique) pollen allergens. In the modified test, the reactivity with the shared CHO will be blocked and positives will be reported only for the more relevant allergens.
- When the serum will be negative for all of the pollen allergens, both the shared CHO and the unique allergens, no positives will be reported.
Cases 1 and 2 are shown in Appendix-1
APPENDIX-1
For the true negative sample (case-1):
For the true positive sample (case-2):
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