Diagnostic Tests for Allergies
Diagnostic tests for Allergies:
Respiratory allergies can be difficult to diagnose and thus may be both over-diagnosed and under-diagnosed at different times. A full evaluation by a medical professional, primary care physician or nurse practitioner, pediatrician, in conjunction with an allergist and asthma specialist, as indicated, is necessary to properly diagnose respiratory allergies and the allergens that cause them.
The most common form of testing for respiratory allergies is skin testing, most often the "scratch test". This test includes putting a small amount of a possible allergen on the skin of the arm or back, then scratching or pricking the skin so the substance inters the body. The patient is then observed for a reaction to that substance, such as redness or swelling. Multiple possible allergens can be tested at one time.
Allergies Tests: Book Excerpts
Home Diagnostic Testing
These home medical tests may be relevant to Allergies:
- Allergies -- Related Home Tests
- Food Allergies & Intolerances: Home Testing:
Allergies Diagnosis: Book Excerpts
Tests and diagnosis discussion for Allergies:
Something in the Air Airborne Allergens: NIAID (Excerpt)
If the patient's medical history indicates that the symptoms recur at
the same time each year, the physician will work under the theory that a
seasonal allergen (like pollen) is involved. Properly trained specialists
recognize the patterns of potential allergens common during local seasons and
the association between these patterns and symptoms. The medical history
suggests which allergens are the likely culprits. The doctor also will examine
the mucous membranes, which often appear swollen and pale or bluish in persons
with allergic conditions.
Skin Tests
Doctors use skin tests to determine whether a patient has IgE antibodies in
the skin that react to a specific allergen. The doctor will use diluted extracts
from allergens such as dust mites, pollens, or molds commonly found in the local
area. The extract of each kind of allergen is injected under the patient's skin
or is applied to a tiny scratch or puncture made on the patient's arm or
back.
Skin tests are one way of measuring the level of IgE antibody in a patient.
With a positive reaction, a small, raised, reddened area (called a wheal) with a
surrounding flush (called a flare) will appear at the test site. The size of the
wheal can give the physician an important diagnostic clue, but a positive
reaction does not prove that a particular pollen is the cause of a patient's
symptoms. Although such a reaction indicates that IgE antibody to a specific
allergen is present in the skin, respiratory symptoms do not necessarily
result.
Blood Tests
Although skin testing is the most sensitive and least costly way to identify
allergies in patients, some patients such as those with widespread skin
conditions like eczema should not be tested using that method. There are other
diagnostic tests that use a blood sample from the patient to detect levels of
IgE antibody to a particular allergen. One such blood test is called the RAST
(radioallergosorbent test), which can be performed when eczema is present or if
a patient has taken medications that interfere with skin testing. (Source: excerpt from Something in the Air Airborne Allergens: NIAID)
Allergies: NWHIC (Excerpt)
Often skin tests
or blood tests are used to determine specific antibody levels reacting to
a certain allergen. If there are unusually high levels of an antibody
known as IgE, it is a good indication of an allergic reaction. (Source: excerpt from Allergies: NWHIC)
Diagnosis of Allergies: medical news summaries:
The following medical news items
are relevant to diagnosis of Allergies:
Diagnostic Tests for Allergies: Online Medical Books
16 MEDICAL BOOKS ONLINE!
Review excerpts from medical books online, free, without registration,
for more information about the diagnostic tests for Allergies.
Urticaria:
Physical examination
(The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter)
A complete physical is required to rule out infection or other systemic diseases. An urticarial wheal is usually well demarcated. It begins as an erythematous area, which then develops a white center. The size of the wheal can vary from 2 mm to well over 30 cm. The rash is usually pruritic, especially when it occurs on the palms of the hand and the soles of the feet. Most often, the wheal will disappear within 3 to 4 hours of onset. The accompanying angioedema can last for a couple of days. The skin will return to normal once the wheal is gone.
Testing
A. Laboratory tests. Routine tests include (a) complete blood count to look for eosinophilia, neoplastic disorders, and occult infection; (b) thyroid studies (thyroxine and thyroid-stimulating hormone; (c) erythrocyte sedimentation rate to help rule out connective tissue disorders and occult infection, urine analysis with urine culture, chemical profile, stool cultures for parasites, liver function tests, and an antinuclear antibody test. Other tests can include immunoglobulins, prick testing, rheumatoid factor, cryoglobulins, serum complement, and skin biopsy. However, laboratory tests often do not provide answers beyond those obtained in the history (3).
B. Diagnostic imaging. Chest x-ray, sinus, and dental films may help to rule out cancer and infection.
Diagnostic assessment
It is important to rule out underlying conditions such as neoplastic disorders, endocrine disorders, connective tissue diseases, infections, and other disorders. The most significant factors in diagnosing acute urticaria are the history and physical examination. Facts must be obtained concerning food or drug ingestion, insect stings, current infections, or physical triggers such as cold or heat. Most acute urticarial reactions resolve spontaneously, but some continue and become chronic in nature. Of the chronic urticaria, a cause is found in only a few of these patients, with more than 75% of them having an idiopathic disorder (4).
References
1. Beltrani VS. Allergic dermatoses. Med Clin North Am 1998;82(5):1105–1133.
2. Greaves MW, Sabroe RA. ABC of allergies. Allergy and the skin. I—Urticaria. BMJ 1998;316(7138):1147–1150.
3. Kozel MM. The effectiveness of a history-based diagnostic approach in chronic urticaria and angioedema. Arch Dermatol 1998;134(12):1575–1580.
4. Greaves MW. Chronic urticaria [published erratum appears in N Engl J Med 1995;
333(16):1091]. N Engl J Med 1995;332(26):1767–1772.
» READ BOOK EXCERPT ONLINE »
Source: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter, 2000
Urticaria/Angioedema:
Diagnostic Approach
(Field Guide to Bedside Diagnosis)
Urticaria appears as transient, mutable wheals with red raised serpiginous borders and clear centers, which often coalesce. Urticaria is experienced by 10% to 20% of the population at some time. Angioedema is well-demarcated localized edema.
The appearance may be helpful. Gyrate hives (erythema gyratum) are associated with internal malignancy. Hives without pseudopods suggest allergy. Small lesions with erythematous flares suggest cholinergic urticaria. Urticarial lesions unchanged for 24 hours suggest vasculitis, especially if associated with scaling or purpura.
» READ BOOK EXCERPT ONLINE »
Source: Field Guide to Bedside Diagnosis, 2007
Urticaria:
Physical assessment
(Signs & Symptoms: A 2-in-1 Reference for Nurses)
Obtain the patient’s vital signs. Perform a complete cardiopulmonary assessment, noting signs and symptoms of shock or respiratory distress. Finish your examination by assessing for urticaria in other areas because new crops may continue to appear.
» READ BOOK EXCERPT ONLINE »
Source: Signs & Symptoms: A 2-in-1 Reference for Nurses, 2007
Urticaria [Hives]:
History and physical examination
(Nursing: Interpreting Signs and Symptoms)
If the patient isn't in distress, obtain a complete history. Does he have any known allergies? Does the urticaria follow a seasonal pattern? Do certain foods or drugs seem to aggravate it? Is there a relationship to physical exertion? Is the patient routinely exposed to chemicals on the job or at home? Has the patient recently changed or used new skin products or detergents? Obtain a detailed drug history, including prescription and over-the-counter drugs. Note any history of chronic or parasitic infection, skin disease, or a GI disorder.
Next, assess respiratory status. Inspect the chest for sternal retractions and accessory muscle use. Auscultate and percuss the chest. Assess cardiac status. Obtain vital signs and pulse oximetry and begin cardiac monitoring. Assess all skin surfaces.
» READ BOOK EXCERPT ONLINE »
Source: Nursing: Interpreting Signs and Symptoms, 2007
Millions suffer from springtime allergies. But experts do have a handle on what sufferers can do to cope with this common problem. Allergies no...
Allergies can leave children feeling sniffly, teary and itchy and take their toll at play and at school. Previously, allergy remedies left children...
What is an allergy and what is it that causes some people to suffer from them? Why do allergies flare up during certain times of the year? Learn...
Sneezing in the sitting room? Coughing in the kitchen? Many common allergens occur primarily indoors and can make your life miserable. Join our panel...
See full list of 15 related videos
» Next page: Diagnosis of Allergies
Rate This Website
What do you think about the features of this website?
Take our user survey and have your say:
Website User Survey
Medical Tools & Articles:
Next articles:
Tools & Services:
Medical Articles:
Forums & Message Boards
- Ask or answer a question at the Boards:
