|
Division
of Sino-Nasal Disorders and Allergy
Diagnostic Services
The division offers the following tests on-site:
CT Scans of the Sinus
A computed tomography (CT) scan is the type of image preferred for analyzing
the anatomy of the sinuses. At the Division of Sino-Nasal Disorders
and Allergy, the physician always orders a CT scan before suggesting
sinus surgery.
Acoustic Rhinometry
Because sound travels at a known speed, reflected sound can provide
information about the size and shape of a cavity. In an acoustic rhinometric
test, a nosepiece transmits an audible signal into the patient's nose.
An attached device analyzes the echo that bounces back and creates a
visual display that represents the size and shape of the nasal cavity.
The examination is not invasive and takes 2 to 5 minutes.
Nasal Endoscopy
An endoscope is a slender instrument with a video camera attached. The
endoscope is inserted about 3 inches into the nose to enable the physician
to see onscreen the outflow tracts of the sinuses and the nasopharynx.
Before endoscopy the nose is decongested and anesthetized with sprays.
The anesthetic spray usually leaves the throat numb for about 30 minutes.
The procedure rarely causes discomfort. Patients may resume normal activities
after the examination.
Mucociliary Transport Study
This test evaluates the ability of the lining of the nose to carry the
mucus, which cleanses the nose. Patients with abnormalities of the mucus
or cilia (the normal microscopic structures that move the mucus within
the nose) have increased nasal problems. Examples of patients with impaired
mucociliary transport are those with cystic fibrosis, primary ciliary
dysmotility syndrome, Kartageners syndrome, or repeated, prolonged infections.
Mechanical cleaning of the nose with topical antibiotics and saline
solution is important in treating this condition.
Sinus Secretion Aspiration
By suctioning the secretion in the sinuses and analyzing it, a specialist
can determine what kinds of bacteria may be causing infections. Suctioning
is painless and takes only moments. The specimen is
sent to the microbiology laboratory for microscopic analysis and culture.
The patient is informed of the results of the procedure within days,
and the most appropriate antibiotic to treat the infection can be prescribed.
Using a culture to identify the specific type of bacteria involved
is increasingly important because of the rise in microbial resistance
to antibiotics. The goal in prescribing an antibiotic is to target and
destroy the microbe causing the infection, in order not to expose
a range of bacteria to a general medication and thereby increasing the
resistance of several types of microbes.
Allergy Testing
Tests for Allergic Reactions to Inhalants
To determine if a person is allergic to an inhalant -- that is, an allergen
that can be inhaled, such as pollen, mold, cat dander, or dust mites
-- we use a form of skin testing known as skin endpoint titration. In
this procedure, a minute amount of the suspected allergen is placed
under the top layer of the skin on the upper arm. In
contrast to skin-prick testing, skin endpoint titration shows not only
what a person is allergic to but also how allergic he or she is.
Tests for Contact Allergies
We use patch testing to determine the cause of a contact allergy --
that is, an allergy that results after a person comes into contact with
an allergen. Common causes of contact allergies are makeup and latex.
A patch test is used to test whether a substance that should not be
injected into the skin -- for example, metals such as nickel --
causes an allergy.
In a patch test, the suspected allergen is attached to
a nonreactive backing, which holds the allergen against the skin for
48 to 72 hours.
Tests for Food Allergies
An adverse reaction to food can be categorized as either food intolerance
or food allergy. The main difference between these two is that food
intolerance does not involve the immune system; a food allergy does.
Food intolerance can usually be helped by some means, such as by taking
a dietary enzyme supplement. The symptoms of a food allergy may be treatable,
but the allergy itself may not be correctable.
A common example of food intolerance is that caused by lactose deficiency.
A person with lactose deficiency experiences discomfort and other symptoms
after eating dairy products because his or her body does not produce
enough lactase, the enzyme needed to digest dairy foods. A person with
lactose intolerance can address the problem by taking a lactase supplement.
In contrast, an allergy to dairy products cannot be corrected by taking
a supplement.
The eight most common food allergens -- milk, eggs, peanuts, tree nuts,
soy, wheat, fish, and shellfish -- cause more than 90 percent of all
allergic reactions to foods.
Many tests for food allergy involve testing for immunoglobulin E (IgE).
Immunoglobulins are proteins. Most help protect the body from infection.
IgE can be different. In about 20 percent of humans, IgE reacts against
substances that are harmless, such as pollen grains, animal dander,
and some food proteins. It is involved in causing allergic asthma and
allergic rhinitis (hay fever) and, in many cases, the symptoms of sneezing,
swelling, redness, and itchiness. The people who suffer from allergies
are people whose IgE reacts to allergens.
To diagnose food allergies, the Division of Sino-Nasal Disorders and
Allergy uses:
-
Elimination challenge diets. Elimination
diets are an essential part of diagnosing food allergies and are
used to test reactions to foods that are not necessarily associated
with high levels of IgE. In the diet, the patient does not eat a
specific food for five days. If the patient is allergic to the withdrawn
food, the period of abstinence makes him or her much more sensitive
to it. On the sixth day, the patient is "challenged" with
the food -- that is, he or she eats a small portion of it. If adverse
symptoms occur -- such as itching, gastrointestinal distress, facial
pressure, or nasal congestion -- the patient is allergic to the
food.
-
In vitro testing, including radioallergosorbent
(RAST) tests. The division uses in vitro testing to detect
allergies in patients who cannot undergo skin testing or who have
a potentially life-threatening allergy, such as peanut anaphylaxis.
In vitro testing is done outside a patient’s body. It involves
taking a blood sample from the patient and determining what kinds
of IgE and how much of each kind are present.
A radioallergosorbent (RAST) test is a
blood test in which a blood sample is placed on a disc that contains
specific food proteins. If the person who provided the blood is allergic
to that food, the blood develops specific antibodies in response to
the food proteins. A high level of antibodies suggests a possible
food allergy. A RAST test is very sensitive. If a RAST test shows
no elevation in response to a food, then the patient does not have
an IgE-mediated allergy to it.
|
