Diagnostic Tests for Food allergies
Food allergies: Diagnostic Tests
The list of diagnostic tests
mentioned in various sources as
used in the diagnosis of Food allergies
includes:
- Diet diary
- Elimination diet - remove the suspect food and see if the allergy is avoided.
- Skin challenge tests
- Diet changes - chaging the diet can test whether a particular food is the cause.
- Double-blind food challenge
- Cytotoxicity testing - a controversial test of dubious value.
- Subcutaneous provocative challenge - a controversial test of dubious value.
- Immune complex assay - a controversial test of dubious value.
- IgG subclass assay - a controversial test of dubious value.
Food allergies Tests: Book Excerpts
Home Diagnostic Testing
These home medical tests may be relevant to Food allergies:
- Allergies -- Related Home Tests
- Food Allergies & Intolerances: Home Testing:
Food allergies Diagnosis: Book Excerpts
Tests and diagnosis discussion for Food allergies:
Food Allergy and Intolerances, NIAID Fact Sheet: NIAID (Excerpt)
To diagnose food
allergy a doctor must first determine if the patient is having an
adverse reaction to specific foods. This assessment is made with the
help of a detailed patient history, the patient's diet diary, or an
elimination diet.
The first of these techniques is the most
valuable. The physician sits down with the person suspected of
having a food allergy and takes a history to determine if the facts
are consistent with a food allergy. The doctor asks such questions
as:
- What was the timing of the reaction? Did the reaction come on
quickly, usually within an hour after eating the food?
- Was allergy treatment successful? (Antihistamines should
relieve hives, for example, if they stem from a food allergy.)
- Is the reaction always associated with a certain food?
- Did anyone else get sick? For example, if the person has eaten
fish contaminated with histamine, everyone who ate the fish should
be sick. In an allergic reaction, however, only the person
allergic to the fish becomes ill.
- How much did the patient eat before experiencing a reaction?
The severity of the patient’s reaction is sometimes related to the
amount of food the patient ate.
- How was the food prepared? Some people will have a violent
allergic reaction only to raw or undercooked fish. Complete
cooking of the fish destroys those allergens in the fish to which
they react. If the fish is cooked thoroughly, they can eat it with
no allergic reaction.
- Were other foods ingested at the same time of the allergic
reaction? Some foods may delay digestion and thus delay the onset
of the allergic reaction.
Sometimes a diagnosis cannot be
made solely on the basis of history. In that case, the doctor may
ask the patient to go back and keep a record of the contents of each
meal and whether he or she had a reaction. This gives more detail
from which the doctor and the patient can determine if there is
consistency in the reactions.
The next step some doctors use
is an elimination diet. Under the doctor's direction, the patient
does not eat a food suspected of causing the allergy, like eggs, and
substitutes another food, in this case, another source of protein.
If the patient removes the food and the symptoms go away, the doctor
can almost always make a diagnosis. If the patient then eats the
food (under the doctor's direction) and the symptoms come back, then
the diagnosis is confirmed. This technique cannot be used, however,
if the reactions are severe (in which case the patient should not
resume eating the food) or infrequent.
If the patient's
history, diet diary, or elimination diet suggests a specific food
allergy is likely, the doctor will then use tests that can more
objectively measure an allergic response to food. One of these is a
scratch skin test, during which a dilute extract of the food is
placed on the skin of the forearm or back. This portion of the skin
is then scratched with a needle and observed for swelling or redness
that would indicate a local allergic reaction. If the scratch test
is positive, the patient has IgE on the skin's mast cells that is
specific to the food being tested.
Skin tests are rapid,
simple, and relatively safe. But a patient can have a positive skin
test to a food allergen without experiencing allergic reactions to
that food. A doctor diagnoses a food allergy only when a patient has
a positive skin test to a specific allergen and the history of these
reactions suggests an allergy to the same food.
In some
extremely allergic patients who have severe anaphylactic reactions,
skin testing cannot be used because it could evoke a dangerous
reaction. Skin testing also cannot be done on patients with
extensive eczema.
For these patients a doctor may use blood
tests such as the RAST and the ELISA. These tests measure the
presence of food-specific IgE in the blood of patients. These tests
may cost more than skin tests, and results are not available
immediately. As with skin testing, positive tests do not necessarily
make the diagnosis.
The final method used to objectively
diagnose food allergy is double-blind food challenge. This testing
has come to be the "gold standard" of allergy testing. Various
foods, some of which are suspected of inducing an allergic reaction,
are each placed in individual opaque capsules. The patient is asked
to swallow a capsule and is then watched to see if a reaction
occurs. This process is repeated until all the capsules have been
swallowed. In a true double-blind test, the doctor is also "blinded"
(the capsules having been made up by some other medical person) so
that neither the patient nor the doctor knows which capsule contains
the allergen.
The advantage of such a challenge is that if
the patient has a reaction only to suspected foods and not to other
foods tested, it confirms the diagnosis. Someone with a history of
severe reactions, however, cannot be tested this way. In addition,
this testing is expensive because it takes a lot of time to perform
and multiple food allergies are difficult to evaluate with this
procedure.
Consequently, double-blind food challenges are
done infrequently. This type of testing is most commonly used when
the doctor believes that the reaction a person is describing is not
due to a specific food and the doctor wishes to obtain evidence to
support this judgment so that additional efforts may be directed at
finding the real cause of the reaction.
Exercise-Induced Food
Allergy At least one situation may
require more than the simple ingestion of a food allergen to provoke
a reaction: exercise-induced food allergy. People who experience
this reaction eat a specific food before exercising. As they
exercise and their body temperature goes up, they begin to itch, get
light-headed, and soon have allergic reactions such as hives or even
anaphylaxis. The cure for exercised-induced food allergy is
simple—not eating for a couple of hours before exercising.
Treatment Food allergy is treated
by dietary avoidance. Once a patient and the patient's doctor have
identified the food to which the patient is sensitive, the food must
be removed from the patient's diet. To do this, patients must read
lengthy, detailed ingredient lists on each food they are considering
eating. Many allergy-producing foods such as peanuts, eggs, and
milk, appear in foods one normally would not associate them with.
Peanuts, for example, are often used as a protein source and eggs
are used in some salad dressings. The FDA requires ingredients in a
food to appear on its label. People can avoid most of the things to
which they are sensitive if they read food labels carefully and
avoid restaurant-prepared foods that might have ingredients to which
they are allergic.
In highly allergic people even minuscule
amounts of a food allergen (for example, 1/44,000 of a peanut
kernel) can prompt an allergic reaction. Other less sensitive people
may be able to tolerate small amounts of a food to which they are
allergic.
Patients with severe food allergies must be
prepared to treat an inadvertent exposure. Even people who know a
lot about what they are sensitive to occasionally make a mistake. To
protect themselves, people who have had anaphylactic reactions to a
food should wear medical alert bracelets or necklaces stating that
they have a food allergy and that they are subject to severe
reactions. Such people should always carry a syringe of adrenaline
(epinephrine), obtained by prescription from their doctors, and be
prepared to self-administer it if they think they are getting a food
allergic reaction. They should then immediately seek medical help by
either calling the rescue squad or by having themselves transported
to an emergency room. Anaphylactic allergic reactions can be fatal
even when they start off with mild symptoms such as a tingling in
the mouth and throat or gastrointestinal discomfort.
Special
precautions are warranted with children. Parents and caregivers must
know how to protect children from foods to which the children are
allergic and how to manage the children if they consume a food to
which they are allergic, including the administration of
epinephrine. Schools must have plans in place to address any
emergency.
There are several medications that a patient can
take to relieve food allergy symptoms that are not part of an
anaphylactic reaction. These include antihistamines to relieve
gastrointestinal symptoms, hives, or sneezing and a runny nose.
Bronchodilators can relieve asthma symptoms. These medications are
taken after people have inadvertently ingested a food to which they
are allergic but are not effective in preventing an allergic
reaction when taken prior to eating the food. No medication in any
form can be taken before eating a certain food that will reliably
prevent an allergic reaction to that food.
There are a few
non-approved treatments for food allergies. One involves injections
containing small quantities of the food extracts to which the
patient is allergic. These shots are given on a regular basis for a
long period of time with the aim of "desensitizing" the patient to
the food allergen. Researchers have not yet proven that allergy
shots relieve food allergies.
Infants and Children
Milk and soy allergies are particularly common in
infants and young children. These allergies sometimes do not involve
hives and asthma, but rather lead to colic, and perhaps blood in the
stool or poor growth. Infants and children are thought to be
particularly susceptible to this allergic syndrome because of the
immaturity of their immune and digestive systems. Milk or soy
allergies in infants can develop within days to months of birth.
Sometimes there is a family history of allergies or feeding
problems. The clinical picture is one of a very unhappy colicky
child who may not sleep well at night. The doctor diagnoses food
allergy partly by changing the child's diet. Rarely, food challenge
is used.
If the baby is on cow's milk, the doctor may
suggest a change to soy formula or exclusive breast milk, if
possible. If soy formula causes an allergic reaction, the baby may
be placed on an elemental formula. These formulas are processed
proteins (basically sugars and amino acids). There are few if any
allergens within these materials. The doctor will sometimes
prescribe corticosteroids to treat infants with severe food
allergies. Fortunately, time usually heals this particular
gastrointestinal disease. It tends to resolve within the first few
years of life.
Exclusive breast feeding (excluding all other
foods) of infants for the first 6 to 12 months of life is often
suggested to avoid milk or soy allergies from developing within that
time frame. Such breast feeding often allows parents to avoid
infant-feeding problems, especially if the parents are allergic (and
the infant therefore is likely to be allergic). There are some
children who are so sensitive to a certain food, however, that if
the food is eaten by the mother, sufficient quantities enter the
breast milk to cause a food reaction in the child. Mothers sometimes
must themselves avoid eating those foods to which the baby is
allergic.
There is no conclusive evidence that breast
feeding prevents the development of allergies later in life. It
does, however, delay the onset of food allergies by delaying the
infant's exposure to those foods that can prompt allergies, and it
may avoid altogether those feeding problems seen in infants. By
delaying the introduction of solid foods until the infant is 6
months old or older, parents can also prolong the child's
allergy-free period.
Controversial Issues There are
several disorders thought by some to be caused by food allergies,
but the evidence is currently insufficient or contrary to such
claims. It is controversial, for example, whether migraine headaches
can be caused by food allergies. There are studies showing that
people who are prone to migraines can have their headaches brought
on by histamines and other substances in foods. The more difficult
issue is whether food allergies actually cause migraines in such
people. There is virtually no evidence that most rheumatoid
arthritis or osteoarthritis can be made worse by foods, despite
claims to the contrary. There is also no evidence that food
allergies can cause a disorder called the allergic tension fatigue
syndrome, in which people are tired, nervous, and may have problems
concentrating, or have headaches.
Cerebral allergy is a term
that has been applied to people who have trouble concentrating and
have headaches as well as other complaints. This is sometimes
attributed to mast cells degranulating in the brain but no other
place in the body. There is no evidence that such a scenario can
happen, and most doctors do not currently recognize cerebral allergy
as a disorder.
Another controversial topic is environmental
illness. In a seemingly pristine environment, some people have many
non-specific complaints such as problems concentrating or
depression. Sometimes this is attributed to small amounts of
allergens or toxins in the environment. There is no evidence that
such problems are due to food allergies.
Some people believe
hyperactivity in children is caused by food allergies. But
researchers have found that this behavioral disorder in children is
only occasionally associated with food additives, and then only when
such additives are consumed in large amounts. There is no evidence
that a true food allergy can affect a child's activity except for
the proviso that if a child itches and sneezes and wheezes a lot,
the child may be miserable and therefore more difficult to guide.
Also, children who are on anti-allergy medicines that can cause
drowsiness may get sleepy in school or at home.
Controversial
Diagnostic Techniques One controversial
diagnostic technique is cytotoxicity testing, in which a food
allergen is added to a patient's blood sample. A technician then
examines the sample under the microscope to see if white cells in
the blood "die." Scientists have evaluated this technique in several
studies and have not been found it to effectively diagnose food
allergy.
Another controversial approach is called sublingual
or, if it is injected under the skin, subcutaneous provocative
challenge. In this procedure, dilute food allergen is administered
under the tongue of the person who may feel that his or her
arthritis, for instance, is due to foods. The technician then asks
the patient if the food allergen has aggravated the arthritis
symptoms. In clinical studies, researchers have not shown that this
procedure can effectively diagnose food allergies.
An immune
complex assay is sometimes done on patients suspected of having food
allergies to see if there are complexes of certain antibodies bound
to the food allergen in the bloodstream. It is said that these
immune complexes correlate with food allergies. But the formation of
such immune complexes is a normal offshoot of food digestion, and
everyone, if tested with a sensitive enough measurement, has them.
To date, no one has conclusively shown that this test correlates
with allergies to foods.
Another test is the IgG subclass
assay, which looks specifically for certain kinds of IgG antibody.
Again, there is no evidence that this diagnoses food allergy.
Controversial
Treatments Controversial treatments
include putting a dilute solution of a particular food under the
tongue about a half hour before the patient eats that food. This is
an attempt to "neutralize" the subsequent exposure to the food that
the patient believes is harmful. As the results of a carefully
conducted clinical study show, this procedure is not effective in
preventing an allergic reaction.
Summary Food
allergies are caused by immunologic reactions to foods. There
actually are several discrete diseases under this category, and a
number of foods that can cause these problems.
After one
suspects a food allergy, a medical evaluation is the key to proper
management. Treatment is basically avoiding the food(s) after it is
identified. People with food allergies should become knowledgeable
about allergies and how they are treated, and should work with their
physicians.
Resources
HOTLINE:National Jewish
Medical and Research Center in Denver.
Nurses available to
answer questions
1/800/222-LUNG
http://www.njc.org/ALLERGY
REFERRALS:American Academy of Allergy, Asthma and
Immunology
611 East Wells Street
Milwaukee, WI
53202
1/800/822-2762.
http://www.aaaai.org/scripts/find-a-doc/main.aspEXTRACTS
FOR ALLERGY TESTING:U.S. Food and Drug
Administration
Center for Biologics Evaluation and
Research
1/800/835-4709
http://www.fda.gov/cber/index.htmlECZEMA:National
Arthritis, Musculoskeletal and Skin Diseases Information
Clearinghouse
One AMS Circle
Bethesda, MD
20892-3675
301/495-4484
http://www.nih.gov/niams/American
Academy of Dermatology
930 N. Meacham Rd.
Schaumburg, IL
60173
1/888/462-DERM
http://www.aad.org/Eczema
Association
1221 S.W. Yamhill, Suite 303
Portland, OR
97205
503/228-4430
LACTOSE INTOLERANCE
and
CELIAC SPRUE:National Digestive Diseases
Information Clearinghouse
Box NDDIC
Bethesda, MD
20892
301/654-3810
http://www.niddk.nih.gov/health/digest/pubs/lactose/lactose.htmhttp://www.niddk.nih.gov/health/digest/pubs/celiac/index.htmFOOD
CONTENTS: U.S. Department of Agriculture
Food and
Nutrition Information Center
301/436-7725
http://www.nalusda.gov/fnic/index.htmlRECIPES:
American Dietetic Association
216 W. Jackson
Boulevard
Chicago, IL 60606-6995
1/800/877-1600
http://www.eatright.org/RESOURCES:Food
Allergy and Anaphylaxis Network
10400 Eaton Place, Suite
107
Fairfax, VA 22030
1/800/929-4040
http://www.foodallergy.org/American
College of Allergy, Asthma and Immunology
85 W. Algonquin Road,
Suite 550
Arlington Heights, IL 60005
1/800/842-7777
http://allergy.mcg.edu/Asthma
and Allergy Foundation of America
1125 15
th Street,
N.W., Suite 502
Washington, DC 20036
1/800/7-ASTHMA
http://www.aafa.org/ (Source: excerpt from
Food Allergy and Intolerances, NIAID Fact Sheet: NIAID)
Food Allergy and Intolerances, NIAID Fact Sheet: NIAID (Excerpt)
One controversial
diagnostic technique is cytotoxicity testing, in which a food
allergen is added to a patient's blood sample. A technician then
examines the sample under the microscope to see if white cells in
the blood "die." Scientists have evaluated this technique in several
studies and have not been found it to effectively diagnose food
allergy.
Another controversial approach is called sublingual
or, if it is injected under the skin, subcutaneous provocative
challenge. In this procedure, dilute food allergen is administered
under the tongue of the person who may feel that his or her
arthritis, for instance, is due to foods. The technician then asks
the patient if the food allergen has aggravated the arthritis
symptoms. In clinical studies, researchers have not shown that this
procedure can effectively diagnose food allergies.
An immune
complex assay is sometimes done on patients suspected of having food
allergies to see if there are complexes of certain antibodies bound
to the food allergen in the bloodstream. It is said that these
immune complexes correlate with food allergies. But the formation of
such immune complexes is a normal offshoot of food digestion, and
everyone, if tested with a sensitive enough measurement, has them.
To date, no one has conclusively shown that this test correlates
with allergies to foods.
Another test is the IgG subclass
assay, which looks specifically for certain kinds of IgG antibody.
Again, there is no evidence that this diagnoses food allergy.
Controversial
Treatments
Controversial treatments
include putting a dilute solution of a particular food under the
tongue about a half hour before the patient eats that food. This is
an attempt to "neutralize" the subsequent exposure to the food that
the patient believes is harmful. As the results of a carefully
conducted clinical study show, this procedure is not effective in
preventing an allergic reaction.
Summary
Food
allergies are caused by immunologic reactions to foods. There
actually are several discrete diseases under this category, and a
number of foods that can cause these problems.
After one
suspects a food allergy, a medical evaluation is the key to proper
management. Treatment is basically avoiding the food(s) after it is
identified. People with food allergies should become knowledgeable
about allergies and how they are treated, and should work with their
physicians.
Resources
HOTLINE:
National Jewish
Medical and Research Center in Denver.
Nurses available to
answer questions
1/800/222-LUNG
http://www.njc.org/
ALLERGY
REFERRALS:
American Academy of Allergy, Asthma and
Immunology
611 East Wells Street
Milwaukee, WI
53202
1/800/822-2762.
http://www.aaaai.org/scripts/find-a-doc/main.asp
EXTRACTS
FOR ALLERGY TESTING:
U.S. Food and Drug
Administration
Center for Biologics Evaluation and
Research
1/800/835-4709
http://www.fda.gov/cber/index.html
ECZEMA:
National
Arthritis, Musculoskeletal and Skin Diseases Information
Clearinghouse
One AMS Circle
Bethesda, MD
20892-3675
301/495-4484
http://www.nih.gov/niams/
American
Academy of Dermatology
930 N. Meacham Rd.
Schaumburg, IL
60173
1/888/462-DERM
http://www.aad.org/
Eczema
Association
1221 S.W. Yamhill, Suite 303
Portland, OR
97205
503/228-4430
LACTOSE INTOLERANCE
and CELIAC SPRUE:
National Digestive Diseases
Information Clearinghouse
Box NDDIC
Bethesda, MD
20892
301/654-3810
http://www.niddk.nih.gov/health/digest/pubs/lactose/lactose.htm
http://www.niddk.nih.gov/health/digest/pubs/celiac/index.htm
FOOD
CONTENTS:
U.S. Department of Agriculture
Food and
Nutrition Information Center
301/436-7725
http://www.nalusda.gov/fnic/index.html
RECIPES:
American Dietetic Association
216 W. Jackson
Boulevard
Chicago, IL 60606-6995
1/800/877-1600
http://www.eatright.org/
RESOURCES:
Food
Allergy and Anaphylaxis Network
10400 Eaton Place, Suite
107
Fairfax, VA 22030
1/800/929-4040
http://www.foodallergy.org/
American
College of Allergy, Asthma and Immunology
85 W. Algonquin Road,
Suite 550
Arlington Heights, IL 60005
1/800/842-7777
http://allergy.mcg.edu/
Asthma
and Allergy Foundation of America
1125 15th Street,
N.W., Suite 502
Washington, DC 20036
1/800/7-ASTHMA
http://www.aafa.org/ (Source: excerpt from Food Allergy and Intolerances, NIAID Fact Sheet: NIAID)
Diagnosis of Food allergies: medical news summaries:
The following medical news items
are relevant to diagnosis of Food allergies:
Diagnostic Tests for Food 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 Food allergies.
NAUSEA AND VOMITING:
DIAGNOSTIC WORKUP
(Algorithmic Diagnosis of Symptoms and Signs)
The basic workup includes a CBC, sedimentation rate, urinalysis, urine drug screen, chemistry panel and electrolytes, serum amylase, arterial blood gases, stools for occult blood, chest x-ray, EKG, and flat plate of the abdomen. Acute onset of nausea and vomiting with ataxia requires an immediate CT scan of the brain to rule out a cerebellar hemorrhage. A pregnancy test should be routine in women of child-bearing age. If there is fever, febrile agglutinins and a heterophile antibody titer should be done. If there is an abdominal mass, a gallbladder ultrasound and intravenous pyelogram may need to be done. Isotope scanning with iminodiacetic acid derivatives is extremely useful to detect acute cholecystitis. If there is chronic vomiting and abdominal pain, the diagnosis can often be made with an upper GI series, small bowel series, or barium enema.
When there is persistent vomiting with abdominal pain, an exploratory laparotomy may need to be considered. The presence of an abdominal mass or suspected pancreatic or biliary disease merits consideration of a CT scan. However, before ordering expensive diagnostic tests, a general surgeon or gastroenterologist ought to be consulted. Laparoscopy, gastroscopy, esophagoscopy, duodenoscopy, and colonoscopy all need to be considered in the workup. Gastroparesis and intestinal pseudo-obstruction can be ruled out by radioisotope studies and manometry of the stomach and small intestine. Angiography is useful to diagnose mesenteric artery ischemia.
» READ BOOK EXCERPT ONLINE »
Source: Algorithmic Diagnosis of Symptoms and Signs, 2003
Vomiting:
History and physical examination
(Handbook of Signs & Symptoms (Third Edition))
Ask your patient to describe the onset, duration, and intensity of his vomiting. What started the vomiting? What makes it subside? If possible, collect, measure, and inspect the character of the vomitus. (See Vomitus: Characteristics and causes.) Explore any associated complaints, particularly nausea, abdominal pain, anorexia and weight loss, changes in bowel habits or stools, excessive belching or flatus, and bloating or fullness.
Obtain a medical history, noting GI, endocrine, and metabolic disorders; recent infections; and cancer, including chemotherapy or radiation therapy. Ask about current medication use and alcohol consumption. If the patient is a female of childbearing age, ask if she is or could be pregnant. Ask which contraceptive method she’s using.
Inspect the abdomen for distention, and auscultate for bowel sounds and bruits. Palpate for rigidity and tenderness, and test for rebound tenderness. Next, palpate and percuss the liver for enlargement. Assess other body systems as appropriate.
During the examination, keep in mind that projectile vomiting unaccompanied by nausea may indicate increased intracranial pressure, a life-threatening emergency. If this occurs in a patient with CNS injury, you should quickly check his vital signs. Be alert for widened pulse pressure or bradycardia.
» READ BOOK EXCERPT ONLINE »
Source: Handbook of Signs & Symptoms (Third Edition), 2006
Vomiting:
History and physical examination
(Professional Guide to Signs & Symptoms (Fifth Edition))
Ask your patient to describe the onset, duration, and intensity of his vomiting. What started it? What makes it subside? If possible, collect, measure, and inspect the character of the vomitus. (See Vomitus: Characteristics and causes.) Explore any associated complaints, particularly nausea, abdominal pain, anorexia and weight loss, changes in bowel elimination patterns or the appearance of stools, excessive belching or flatus, and bloating or fullness.
Obtain a medical history, noting GI, endocrine, and metabolic disorders; recent infections; and cancer, including chemotherapy or radiation therapy. Ask about current medication use and alcohol consumption. If the patient is a female of childbearing age, ask if she is or could be pregnant and which contraceptive method she uses.
Inspect the abdomen for distention, and auscultate for bowel sounds and bruits. Palpate for rigidity and tenderness, and test for rebound tenderness. Next, palpate and percuss the liver for enlargement. Assess other body systems as appropriate.
During the examination, keep in mind that projectile vomiting unaccompanied by nausea may indicate increased intracranial pressure, a life-threatening emergency. If this occurs in a patient with a CNS injury, quickly check his vital signs. Be alert for widened pulse pressure or bradycardia.
» READ BOOK EXCERPT ONLINE »
Source: Professional Guide to Signs & Symptoms (Fifth Edition), 2006
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
Nausea and Vomiting:
Physical examination.
(The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter)
A directed physical examination is dictated by the findings on history, but the following are areas of key importance:
A. Vital signs. Focus on presence of fever, pulse, and blood pressure to assess hydration, and respiratory rate to look for acidosis-related hyperventilation.
B. Skin, eyes, mucous membranes. Look for dehydration and signs of jaundice.
C. Signs of systemic infection. Pay special attention to examining the lung and the costovertebral angle for tenderness.
D. A detailed abdominal examination should include inspection, auscultation, palpation, percussion, areas of tenderness, rebound, guarding, hepatomegaly, Murphy’s sign, stool for occult blood, and bimanual pelvic examination.
Testing.
Most cases of nausea and vomiting seen in a generalist’s office will not require laboratory testing. If the diagnosis is still unclear after history and physical examination, the laboratory workup can be classified into primary, secondary, and tertiary on the basis of their utility and ability to detect disease with an urgent need for diagnosis.
A. Primary tests include electrolytes, glucose, renal and liver function tests, amylase, urinalysis, stool for white blood cells, pregnancy test, and plain films of the abdomen or abdominal ultrasound if pain is a prominent feature of the presentation.
B. Secondary tests include abdominal ultrasound if not already done, upper GI series or upper endoscopy, stool culture, thyroid-stimulating hormone, electrocardiogram, and chest x-ray study.
C. Tertiary tests include lower endoscopy, computed tomography or magnetic resonance imaging studies, urine toxicology, urine porphyrins, and, in many instances, specialty consultation.
Diagnostic assessment
The diagnostic assessment of nausea and vomiting will benefit from a structured approach that includes the following:
A. A differential diagnosis based on age and reproductive status.
B. Attention to GI versus systemic causes of nausea and vomiting.
C. Special attention to the potentially more urgent nature of cases of nausea and vomiting that are often accompanied by abdominal pain (Chapter 9.1).
References
1. Avner JR. Vomiting. In: Schwartz MW, ed. Pediatric primary care—a problem oriented approach, 3rd ed. Chicago: Yearbook Medical Publishers, 1997:397–406.
2. Sorgel KH, Greenberger NJ. Nausea and vomiting in the diabetic patient. Hosp Pract (Off Ed) 1998;33:14–16.
3. Bouchier IAD. Nausea, vomiting. In: Bouchier IAD, Ellis H, Flemming P, eds. Index of differential diagnosis, 13th ed. Oxford: Butterworth Heinman Publishers, 1996:
446,710–713.
4. Brzana RJ, Koch KL. Gastroesophageal reflux disease presenting with intractable nausea. Ann Intern Med 1997;126:704–707.
5. Withers GD, Silburn SR, Forbes DA. Precipitants and aetiology of cyclic vomiting syndrome. Acta Pediatr 1998;87:272–277.
» READ BOOK EXCERPT ONLINE »
Source: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter, 2000
Nausea/Vomiting:
Diagnostic Approach
(Field Guide to Bedside Diagnosis)
Neurological vomiting may be projectile (forceful emesis without prior nausea), positional, or associated with other neurological signs. Central vomiting (chemoreceptor trigger zone stimulation, usually caused by toxins) is alleviated by antidopaminergic medications, which do not work well when treating nausea due to mechanical causes such as obstruction.
Early morning nausea suggests pregnancy or metabolic causes (e.g., uremia). Vomiting of a large amount of undigested food 4 to 6 hours after eating is consistent with gastric retention resulting from pyloric obstruction
or gastroparesis or to esophageal disorders such as achalasia or Zencker diverticulum. Feculent vomiting suggests intestinal obstruction or gastrocolic fistula.
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Source: Field Guide to Bedside Diagnosis, 2007
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.
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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.
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Source: Signs & Symptoms: A 2-in-1 Reference for Nurses, 2007
Vomiting:
Physical assessment
(Signs & Symptoms: A 2-in-1 Reference for Nurses)
Inspect the abdomen for distention, and auscultate for bowel sounds and bruits. Palpate for rigidity and tenderness, and test for rebound tenderness. Next, palpate and percuss the liver for enlargement. Assess other body systems as appropriate.
During the assessment, keep in mind that projectile vomiting unaccompanied by nausea may indicate increased intracranial pressure (ICP), a life-threatening emergency. If this occurs in a patient with CNS injury, you should quickly check his vital signs. Be alert for widened pulse pressure or bradycardia.
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Source: Signs & Symptoms: A 2-in-1 Reference for Nurses, 2007
Regurgitation and Vomiting:
Diagnostic Approach: Regurgitation
(The Diagnostic Approach to Symptoms and Signs in Pediatrics)
In infantwith regurgitation who is otherwise well and gaining weight, mostlikely diagnosis is normal variation or mild gastroesophageal reflux.Persistent regurgitation with poorweight gain, respiratory symptoms, or symptoms suggesting esophagitisrequires investigation.Upper GI radiographic series excludesother causes of esophageal obstruction. Most reliable test for gastroesophagealreflux is esophageal pH monitoring. Endoscopy with biopsy can confirmdiagnosis of esophagitis.Other investigations depend on history,physical exam, and results of the above studies.
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Source: The Diagnostic Approach to Symptoms and Signs in Pediatrics, 2006
Vomiting:
History and physical examination
(Nursing: Interpreting Signs and Symptoms)
Ask your patient to describe the onset, duration, and intensity of his vomiting. What started the vomiting? What makes it subside? If possible, collect, measure, and inspect the character of the vomitus. (See Vomitus: Characteristics and causes.) Explore associated complaints, particularly nausea, abdominal pain, anorexia and weight loss, changes in bowel habits or stools, excessive belching or flatus, and bloating or fullness.
Obtain a medical history, noting GI, endocrine, and metabolic disorders; recent infections; and cancer, including chemotherapy or radiation therapy. Ask the patient about current medication use and alcohol consumption. If the patient is a female of childbearing age, ask if she is or could be pregnant or which contraceptive method she's using.
Inspect the patient's abdomen for distention and localized bulging, and auscultate for bowel sounds and bruits. Palpate for rigidity and tenderness and test for rebound tenderness. Palpate and percuss the liver for enlargement. Assess the patient's other body systems as appropriate.
During the examination, keep in mind that projectile vomiting unaccompanied by nausea may be an indication of increased intracranial pressure, a life-threatening emergency. If this occurs in a patient with CNS injury, you should quickly check his vital signs. Be alert for widened pulse pressure or bradycardia.
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Source: Nursing: Interpreting Signs and Symptoms, 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.
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Source: Nursing: Interpreting Signs and Symptoms, 2007
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