Testing for Type I Hypersensitivity

Question 1

Testing for allergies typically begins with direct skin testing because this procedure is less expensive and more sensitive than ______testing and provides immediate results.

Answer 1

serological

Question 2

Two types of skin tests are used in clinical practice:

Answer 2

percutaneous tests (also known as prick or puncture tests) and intradermal tests

Question 3

detect hypersensitivity to a wide variety of inhaled or food allergens. In these tests, the clinician uses a needle or pricking device to introduce a small drop of allergen extract into the upper layers of the individual’s skin in the inner forearm or the back. A panel of allergens is routinely used, with each applied to separate sites 2 to 2.5 cm apart

Answer 3

Percutaneous tests

Question 4

A negative control consisting of the ____used for the allergy extract and a positive control of histamine are also included. After ___ __minutes, the clinician examines the testing spots and records the reaction.

Answer 4

diluent ; 15 to 20

Question 5

In a positive test, a __________ reaction will appear at the site where the allergen was applied. Scoring of the reaction is based on the presence or absence of ______ and the diameter of the wheal, with a diameter larger than 3 to 4 mm correlating best with the presence of allergy.

Answer 5

wheal-and-flare; erythema

Question 6

use a greater amount of antigen and are more sensitive than cutaneous tests. However, they are usually performed only if prick tests are negative and allergy is still suspected because they carry a larger risk (0.05%) for anaphylactic reaction than prick tests (0.03%).

Answer 6

Intradermal tests

Question 7

used to administer 0.01 to 0.05 mL of test solution between layers of the skin. The test allergen is diluted 100 to 1,000 times more than the solution
used for cutaneous testing.

Answer 7

1-mL tuberculin syringe

Question 8

This test is performed on the ____ _____or ____ ___ so that if a systemic reaction occurs, a tourniquet can be applied to the arm to help stop the reaction.
After 15 to 20 minutes, the site is inspected for erythema and wheal formation, and the wheal diameter is measured to determine a score.

Answer 8

inner forearm or upper arm

Question 9

Intradermal tests can be used to test for sensitivity to many allergens but have shown no benefit in the diagnosis of

Answer 9

food allergies

Question 10

must be discontinued a few days before testing because they can decrease or inhibit the skin reaction

Answer 10

Antihistamines

Question 11

Improper technique or use of an inappropriate dilution or improperly stored allergen extract can also lead to _________ results

Answer 11

false-negative

Question 12

_________ results can also occur; these may be caused by the patient’s reaction to the diluent, preservative, or contaminants in the allergen extract or to physical trauma to the skin in patients with severe skin dermatographism or eczema.

Answer 12

False-positive

Question 13

In cases where the risk of a harmful reaction is too large, skin disorders are present, or patients cannot discontinue medications before testing, ______ testing for allergen-specific IgE antibodies is indicated.

Answer 13

serological

Question 14

*safer to perform than skin testing; are easier on some patients, especially children or apprehensive
adults; and have excellent analytical sensitivity
*useful in detecting allergies to a number of common triggers, including ragweed, trees, grasses, molds, animal dander, foods, and insect venom

Answer 14

Allergen-specific IgE tests

Question 15

original commercial testing method for determining
specific IgE, was introduced in 1972

Answer 15

radioallergosorbent test (RAST)