Rhinology Allergy Diagnostic Testing Flashcards
Although it is no longer regularly used in the
United States, what test can be used to look for
eosinophils versus neutrophils in the nasal mucus
in an effort to distinguish eosinophilic rhinitis from
other rhinitis?
Nasal cytology
Allergy testing to specific allergens can be done
via which two broad techniques?
● In vivo (skin testing)
● In vitro (serum testing)
What immunoglobulin is being tested for with in
vivo skin testing?
Antigen-specific IgE
What are the two most common locations for
performing skin testing?
● Volar surface of the forearm
● Back
What type of in vivo allergy test is performed
using scratch, prick/puncture, or patch to
challenge a patient by introducing allergen into
the epidermis only?
Epicutaneous testing
What type of in vivo allergy test is performed
using intradermal techniques to place antigen into
the superficial dermis?
Percutaneous testing
What variables impact both epicutaneous and
percutaneous skin testing?
● Age of the skin (very young and very old may be less
sensitive)
● Area of the body being tested (sensitivity: upper back >
lower back > upper arm > lower arm)
● Skin pigmentation (darker skin colors may be less sensitive)
● Concurrent medications
● Potency and biologic stability of the allergen test extract
● Dermatopathology: Dermatographism, eczema → con-
traindications, including degree of sensitization, recent
anaphylaxis, recent exposure, prior immunotherapy
During skin testing, what controls are commonly
used?
● Negative control: Glycerin-saline, saline, allergen diluent
● Positive control: Histamine (10 mg/mL)
During skin testing, what term is used to describe
the white (blanched) raised area at the site of the
allergen application?
The area of erythema that extends beyond this
raised region?
Wheal
Flare
Why is scratch testing (small superficial
lacerations made in the skin, a drop of
concentrated antigen then applied) not recommended for skin testing?
Poor reproducibility, variable sensitivity, poor specificity,
frequent false-positives, painful, and reaction may be due to
trauma to skin instead of reaction to allergen
During an in vivo epicutaneous allergy test, a drop
of antigen is placed on the patient’s skin. The
tester then uses a needle, lancet, or prick device
(single or multiple tines) to puncture or prick the
skin through the drop of antigen and deliver the
antigen to the epidermis. What is this called?
Skin-prick or puncture testing. It is the most commonly
used test.
What instrument(s) can be used to perform a skin prick or puncture test?
Hypodermic needle, solid-bore needle, lancet ± bifurcated
tip, multiple-head devices (more commonly used because
of OSHA concerns regarding inadvertent health care worker
needle sticks)
Pass through the droplet, then the skin at a 45- to 60-
degree angle to the skin, lift and break the skin without
causing bleeding for the prick test; or the skin device can be
passed through the drop at a 90-degree angle to the skin
for puncture test.
After performing a skin prick or puncture, how
long should you wait before assessing the
response?
15 to 20 minutes
How can you assess the allergic response to a skin
test (epicutaneous or percutaneous)?
Direct measurement: Recommended scoring system
● Longest diameter or longest diameter and orthogonal
diameter (perpendicular) of wheal in millimeters
● Presence or absence of flare and size in millimeters as in
preceding
● Presence or absence of pseudopods
Classically based on a 0 to 4 + system: Based on wheal and
flare compared with the negative control and the presence
or absence of pseudopods
Subjective analysis is no longer recommended by the
American Academy of Allergy, Asthma and Immunology
because of interphysician variability in scoring and inter-
pretation.
The American Academy of Allergy, Asthma, and
Immunology guidelines for skin testing
recommend that wheals < 3 mm should not be
considered positive. Why?
Trauma can affect wheal size.
What are the major disadvantages to skin-prick
tests?
Semiqualitative (less objective than intradermal testing).
Low degrees of sensitivity may be missed → false-negative
results.
When should you use an intradermal/
percutaneous allergy test?
When the primary goal of testing is increased sensitivity, or
for evaluating drug or venom anaphylactic reactions
Describe the technique used for single dilutional
intradermal (percutaneous) allergy testing.
- Using a small needle (generally 26- or 27-gauge needle
at 45-degree angle), inject 0.02 to 0.05 mL of antigen
diluted to 1:500 to 1:1000 weight/volume intradermally
(create a 2- to 3-mm bleb in dermis). - Positive control: Histamine (0.001 mg/mL) if needed;
can be excluded if reaction was proven by prick testing.
Negative control also performed. - Wait 10 to 15 minutes, and then assess response.