indications of allergy testing

1. Fawzeia Abo Ali
Prof. of Internal Medicine & Immunology

2. Allergy is a hypersensitivity reaction
initiated by mainly antibody- or
occasionally via cell-mediated response.
About 30 -40% of individuals in
developed countries have allergy,
1. asthma ,(5 - 10%),
2. Rhinitis (10 - 20%)
3. food allergy (1 - 3%).

3. Asthma
A.rhinitis
Anaphlaxis
hives

4. Allergy Diagnosis

5. 1. Asthma
2. Seasonal allergic
rhinitis/conjunctivits
3. Allergic & fungal sinusitis
Major Indications for Allergy
Testing

6. Necessary indications of allergy testing

7. Indicatios of allergy testing in
Asthma
1. Patients exposed to indoor allergens
with persistent asthma
2. To improve management of patients
with:
– Moderate to severe persistent asthma
– Poor control despite appropriate therapy
– Using excessive amounts of medications
– Associated rhinitis or sinusitis
3. Identifying role of agent
– Occupational exposure ,food or drug
4. Before immunotherapy

9. Allergy tests
• In vitro testing:
 Total &specific IgE tests),
 basophil histamine
release test
 Serum mast cell
tryptase .
• In vivo testing:
 ((skin prick testingskin prick testing,
intradermal testing,
 patch testing,
 bronchial provocation
tests,
food challengesfood challenges.

10. 1. Skin prick test

11. 1. Skin prick test
rhinoconjunctivitis,
asthma,
urticaria,
anapylaxis,
atopic eczema
food and drug allergy.
Contraindications:
:
Severe atopic dermatitis
Dermatographism. •
severe reaction to some
allergens
Pregnancy.
Anaphylaxis
B blockers
Indications:
IgE mediated allergy

12. Drug Suppression
Abstinence before
testing
Antihistamines
1st generation H1-blocker
+++ > 2 days
Hydroxyzine
2nd generation H1-blocker
+++ 7 days
Cetirizine, Loratadine, etc.
Ketotifen +++ > 5 days
H2-blocker 0 - + Ø
Glucocorticosteroids
Topical (in test area) + > 1 week 1
NasalInhaled 0 Ø
Systemic/short term (up to 10 d) 0 / (+)
Topical calcineurin inhibitors + > 1 week
Omalizumab ++ > 4 weeks

16. •Patients unable to discontinue antihistamines
Patients with extensive dermatitis/dermatographia
Patients unable to discontinue beta-blockers
•Patients with an anaphylactic
2) Allergen-specific IgE

17. SPT compared with specific IgE
SPT
• more rapidly obtained,
• less expensive, and more
sensitive
• Immediate results
• Generally more sensitive
• Side effect
Specific IgE
• Completely safe
• Not affected by drugs
• It is not affected by skin
disease:

18. Should I do a “blood" test or a
skin test???
• Skin testing remains the "gold
standard" for detection of allergen-
specific IgE
• Positive "RAST" indicate the presence of
allergen-specific IgE in the peripheral
blood (ie that the patient is "sensitised" to
the allergen),NOT necessarly allergic.
• sensitivities of 70% to 80% have been noted
when compared with skin tests.

19. Total IgE levels —
• Although an elevated total IgE may indicate that
the patient has an atopic condition, yet, there is
a large degree of overlap between IgE levels in
people with and without allergic disease, the
utility of total IgE in diagnosing these common
conditions is limited

20. Patch test

21. • Basophil histamine release
• The basophil histamine release test measures
the release of histamine from human peripheral
blood basophils incubated with allergen, basophil
histamine release is not standardized and is
considered an investigative tool for drug, food,
and environmental allergens.

22. The Double blind food challenge
test
(DBPCFC)
 The gold standard for food allergy
diagnosis.
• These consist of double-blind, placebo-controlled
challenges using encapsulated food.
• This test allow diagnosis of food hypersensitivity
whatever its pathogenesis .

23. • Sequentially increasing doses of the suspected
food are administered at intervals of 30 to 60 minutes
until the patient consumes an amount equivalent to a
standard serving size of the food.
• If the patient demonstrates objective evidence of an
allergic reaction then the procedure is halted .

24. Indicated when there is
discordance between the
clinical history and the
results of objective tests.
4. Provocation Testing
The patient inhales saline, and the pulmonary functions are repeated. If
the baseline FEV1 remains stable, the patient inhales increasing doses of
the challenge substance at15- to 30-minute intervals. A decrease in FEV1
of at least 20% following a dose of the substance is considered a positive
response.

25. Case 1
• A 25-year-old nonsmoking graduate student recently
moved into a ground-floor apartment.
• He had a history of childhood asthma that easily
managed by the use of inhaled -agonist as needed.
• Within 1 month, he began to experience nocturnal
attacks, and increased need for his -agonist,β
• Physical examination revealed a pale, boggy nasal
mucosa and diffuse expiratory wheezes.
• Prick skin testing to inhalant allergens revealed 4+
reaction to house dust mite, and 2+ to tree pollen.

26. Case 2
• A 25-year-old woman with a long history of asthma
develops nasal stuffiness. Initial blood tests reveal an
elevated serum IgE (550 kU/L) and eosinophilia 18%.
• Respiratory allergic disease is suspected but RAST and
skin prick testing are negative.
• She subsequently develops fevers, weight loss, foot drop
and pulmonary infiltrates.
• Other causes of eosinophilia elevated IgE were
investigated.
• In this case, specific anti-neutrophil antibodies were
detected, which indicated Churg-Strauss syndrome.

27. Case 3
A .42-year-old nurse is assessed for antibiotic
allergy one week after having developed
generalised urticaria associated with dyspnoea
and near syncope following ingestion of
amoxycillin.
What is the safest initial test for penicillin
allergy?
– Skin prick test
– RAST testing to penicillin

28. Case 4
A six-year-old girl who has history of egg allergy
since she was 12 months, develops +ve (SPT) to
egg white.
• Does the positive skin prick test mean this girl is
still allergic to egg? If not, are there any further
tests that should be performed?
 The majority of egg-allergic children will
lose their allergy to egg by age seven, some of
these children may not lose their SPT reactivity
 Graded challenge is confirmatory

29. Take home messege
• History + skin prick testing remain
the "gold standard" for identifying
relevant allergens.
• A positive RAST in the absence of a
consistent history indicates
sensitisation, not allergy.
• Double blind food challenge test
demonstrates objective evidence for
allergic food reaction .

30. Take home messege (cont.)
• Bronchoprovocation challenges for
asthma are indicated in some situations.
• In the absence of allergic disease,
Elevations of IgE and eosinophilia
,should be investigated.
• In vitro tests offer advantages in some
situations.

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