canis - Articles
Skin: intradermal test
Overview
- Identify potentially important allergens in order to start immunotherapy once a diagnosis of atopy Skin: atopy has been made.
Uses
Alone
- Identify potentially important allergens in order to start immunotherapy Allergen-specific immunotherapy once a diagnosis of atopy Skin: atopy has been made.
In combination
- Diagnosis of atopy in dogs with compatible history, clinical signs and laboratory tests that do not support other differential diagnoses.
- Identification of allergens involved in atopy for desensitizing vaccine production.
- To identify allergens involved in atopy before attempting specific avoidance (however avoidance is rarely practical in dogs) Skin: atopy - allergen avoidance.
Other points
Only undertake intradermal testing if animal owner is willing to commit to at least 1 year of hyposensitization treatment if test confirms diagnosis of atopy.Sampling
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Tests
Methodologies
- Skin testing is performed with dogs in lateral recumbency usually with the use of sedation, eg medetomidine Medetomidine.
- An area approximately 15x15 cm over the lateral trunk is clipped.
- Injection sites are marked with a felt-tip marker.
- 0.05 ml of each of a panel of allergens is injected into the dermis with histamine and saline used as positive and negative controls respectively.
- Injection sites are examined 15 min later for immediate reaction
, and at 24-48 hours for delayed reaction.
Availability
- Intradermal skin testing is available by referral to a veterinary dermatologist.
Intradermal skin test panels are available but testing and interpretation should only be undertaken by experienced practitioner.
Validity
Sensitivity
- 66-90%.
- A positive intradermal skin test indicates that animal has skin sensitizing antibody.
A positive test does not necessarily mean that the allergen is clinically significant in that animal.
Specificity
- Completely negative results are usually because the tentative diagnosis of atopy was incorrect.
Technique intrinsic limitations
- False-positives: may occur if very irritable, inflamed or traumatized test site, eg with pyoderma Skin: mucocutaneous pyoderma.
- False-negatives: if drug interference, inherent host factors, eg serious internal disease, testing at the wrong time of year.
Technician extrinsic limitations
- Poor skin test technique may give false-negative or false-positive results.
- Irritant allergens may give false-positive results.
- Insufficient allergenic principle, eg outdated extract may give false-negative results.
Result Data
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Further Reading
Publications
Refereed papers
- Recent references from VetMedResource and PubMed.
- Mueller R S, Bettenay S V & Tideman L (2000) Aero-allergens in canine atopic dermatitis in southeastern Australia based on 1000 intradermal skin tests. Aust Vet J 78, 392-399.
- Codner E C & Lessard P (1993) Comparison of intradermal allergy test and enzyme-linked immunosorbent assay in dogs with allergic skin disease. JAVMA 202, 739.
Other sources of information
- Moriello K A & Mason I S (1995) Eds. Handbook of Small Animal Dermatology.1st edn. Pergamon. pp 33-36. (Concise step-by-step procedure.)
- Scott D W, Miller W H, Griffin C E (1995) Eds Muller and Kirk's Small Animal Dermatology. 5th edn. W B Saunders Co, USA. (Concise step-by-step procedure).
- Sousa C A & Norton A L (1990) Advances in Methodology for Diagnosis of Allergic Skin Disease. Vet Clin North Am Small Anim Pract 20, 1419-1427.
- Reedy L M & Miller W H (1989) Allergic Skin Diseases of Dogs and Cats. 1st edn. W B Saunders, USA. pp 81-109. (Detailed procedure and interpretation.)