Intradermal testing Flashcards
Tests of cell-mediated immunity
Allergenic extracts are injected intradermally & the sites are monitored for allergic reactions
Allergens
Substance that causes an allergic reaction
Urticaria
Hives
Wheals
Swelling on the surface of the skin
Red welts
Angioedema
Edema of the dermis & subcutaneous tissues
What antibody, leukocyte, and cells are active during allergic reactions
IgE, basophils, and mast cells
What is intradermal testing?
Tests of cell-mediated immunity
What species do we do intradermal testing?
Dogs
Can dogs have allergies to more than one allergen?
Yes
What are the allergens based on?
Geography and patient history
What testing has not been vaildated yet?
Intradermal testing for food allergies
What are reactions triggered by?
Basophils and/or mast cells releasing histamine-containing granule that invoke an inflammatory response
How do you prepare a dog for intradermal testing?
Shave the hair on the lateral thorax
What do you use to mark injection sites?
Felt-tip marker
How far apart should the injection sites be?
2cm
What gauge needle do you use to inject the specifically selected antigen?
26 gauge needle
0.05mLs of specifically selected antigen
When do you evaluate the injection sites?
15 and 30 minutes
How do you grade the sites?
Based on the controls
Measure the diameter of the wheal
What is the positive control?
Histamine
What is the negative contorl?
Saline
What are reasons for false negative reactions?
Subcutaneous injection Too little antigen Drug interference Anergy Inherent host factors Endoparasitism or ectoparasitism Off-season testing Histamine
False negative reactions: Drug interference
Glucocorticoids Antihistamines Tranquilizers Progetational compoinds Drugs that lower blood pressure
False negative reactions: Anergy
Testing during peak hypersensitivity reaction
False negative reactions: Off-season testing
Testing more than 1-2 months after clinical signs have disappeared
False negative reactions: Histamine
Hyporeactivity
What are the reasons for false positive reaction?
Irritant Test allergens Contaminated test allergens Skin-sensitizing antibody only Poor technique Substance that cause nonimmunologic histamine release Irritable skin Dermatographism Mitogenic allergen
False positive reactions: Irritant test allergens
Contain glycerin, house dust, feathers, wool, old and all food preparations
False positive reactions: Contaminated test allergens
Bacteria or fungi
False positive reactions: Poor technique
Traumatic placement of the needle
Dull or burred needle
Too large volume injected
Air injected
False positive reactions: Substances that cause nonimmunologic histamine release
Narcotics
False positive reactions: Irritable skin
Large reactions seen to all infected substances
What does a positive reaction look like?
A raised welt that indicates the animal is allergic to the antigen
What do hypersensitive reactions look like?
Urticaria (hives), wheals, or angioedema
Why do hypersensitivity reactions occur
The dog has allergies to more than one allergen
What are common allergies?
Grass, trees, pollen, molds, dust
What is the goal of intradermal testing?
To create allergy shots to desensitize the animal to the allergens
What is the ELISA test developed for allergies?
ALLERCEPT
What does ALLERCEPT determine?
The specific IgE antibodies in dogs, cats and horses
What does ALLERCEPT test for?
Grasses, trees, weeds, mites, insects, and fungi
How do you do the tuberculin test?
Inject tuberculin intradermally at a site in cervical region or skin fold at the base of the tail
What animals is the tuberculin test commonly performed on?
Cattle and primates
What do animals with Mycobacterium spp develop?
A delayed hypersensitivity reaction to the organism tuberculin
Why is it a delayed reaction?
Because T lymphocytes must migrate to the foreign antigen injected
What does the tuberculin test actually test for?
Mycobacterium
