Transcript Diagnosis of type 1 allergy and immunotherapy .

Diagnosis of type 1 allergy.
Prof. Mohamed Osman Gad ElRab .
College of Medicine & KKUH .
Introduction :
Many patients with various ‫ مختلفه‬clinical problems
are suspected to have an allergic disease , ‫يعني اذا‬
‫جاك مريض حط من اعتباراتك انه عنده حساسيه واغلب هذوال المرضى‬
: ‫هم‬
e.g. . - itching skin rashes.
- upper & lower respiratory symptoms .
- adverse reactions to food .
- adverse reactions to drugs,(antibiotics,
local anesthetics, analgesics ).
- Establishing a correct allergy diagnosis help to
select appropriate therapeutic interventions for
the patient such as :
:
‫اشهر انواع عالج الحساسيه‬
- allergen avoidance ‫ تجنب مثيرات الحساسيه‬.
- medications .
- immunotherapy .
Major indications ‫ دواعي االستخدام االساسيه‬for
allergy testing .
1. patients with rhinitis in whom symptoms
are not controlled by medications .
allergic rhinitis .( IgE- mediated ). ( ‫هذا النوع هو اللي نبحث‬
) ‫عنه بعمل االختبار وهذا النوع هو اللي ما يستجيب للعالجات العاديه‬
non-allergic rhinitis .( non IgE- mediated ) .
infectious .
aspirin hypersensitivity.
non-specific.
Prevalence ‫ معدل االنتشار‬:
60 – 70 % of rhinitis patients have
allergy ( IgE- mediated ).
25 – 34 % of patients with rhinitis develop
asthma within 10 years .
2. patients with persistent ‫ دائم‬symptoms of asthma .
58-80% of asthma patients have immediate
skin test reactivity .
.(Kalliel etal. Chest 1989,96:1336-40).
58% of adult asthmatic patients in Riyadh
have immediate skin test reactivity & specific
IgE to prevalent ‫منتشره‬allergens.
(Gad EL Rab M.O., Annals of Saudi Medicine.1999,19:447-49 ).
It is recommended that all asthma patients
,who require daily therapy ,be evaluated for
allergens as possible contributing ‫ مساهمه‬factors
.
Guidelines for the diagnosis and management of asthma : expert
panel report NIH publication no.98-4051,Bethesda,Md.,1997: 43,45
3. patients with suspected food allergy .
- adverse reactions to food proteins are divided
into :
IgE- mediated
non- IgE mediated .( food intolerance ). ‫عدم‬
) ‫تحمل الطعام مثل بعض الناس اللي يواجهون مشاكل مع حليب الجمالت ( ياااي‬
- approximately 5-6 % of children (younger than
3 years ) and 1.5 – 2 % of the general population
suffer from food allergic disease .
Diagnosis of food allergy is important because
the mainstay ‫ الدعم الرئيسي‬of therapy remains :
1. avoidance of the incriminated ( ‫المسبب للحساسيه‬
) ‫ بعض الناس حساسين من الفول‬foods.
2. education to deal with inadvertent exposure
‫التعليم للتعامل مع الحاالت المفاجئه ( واحد اكل اكل ما درى انه‬
) ‫ يسبب حساسيه‬.
4. patients with suspected drug allergy .
- reliable ‫ فعال ودقيق‬allergy tests for drugs are
available only for penicillin and local anesthetics
‫التخدير الموضعي‬. ‫مهمه جدا‬
- e.g. suspected reaction to penicillin .
prescribe ‫ يوصف له‬alternative antibiotic ‫مضاد‬
‫ حيوي آخر‬.
5. suspected insect sting reactions :
previous suspected systemic reaction to insect
stings .
- identify insect .
- advice immunotherapy. ‫الن الحشرات من‬
‫مثيرات الحساسيه التي ال يمكن التحكم بها ( يعني مب على‬
) ‫كيفك ما تاكل حشرات‬
- e.g. the honey bee & black fire ant
are common causes of anaphylaxis.
‫الحساسيه المفرطه والتي من الممكن ان تؤدي للوفاه وتعالج بـ‬
Epinephrine ( adrenalin )
Types of allergy tests :
1. Immediate- type hypersensitivity skin testing .
a. percutaneous route .( skin prick test ).
b. intradermal route .( injection of allergen
within the dermal layer ).
2. assay ‫ قياس‬for allergen specific IgE antibodies
.
3. Bronchial challenge test .
( occupational asthma ‫) الربو المفتعل‬
- expose patient to allergen and record symptoms.
4. Double- blind food challenge test .
provide definitive ‫ النهائي‬diagnosis of food allergy
when clinical certainty ‫ االعتماد والتاكيد‬is needed .
( because of the low specificity of the skin test
with food allergens ). ‫مهمه‬
1. the skin prick test ( SPT )
(the most commonly used method ) .
1. rapid.
2. accurate ‫ دقيقه‬.
3. cheap.
4. safe procedure. ‫اجراءات‬
5. highly reproducible .
‫تعطي نتائج‬
Principle ‫ المبادئ‬of the skin test :
when allergen extracts are introduced into the skin ,of a
previously sensitized individual , they
cross- link IgE molecules on mast cells which :
release mediators and produce :
- a local wheal and flare reaction .
Site for prick test ‫ اماكن الوخز‬:
• The inner (volar ) ‫ )الراحه ( الباطن‬aspect of the
forearm.
Or :
The skin of the upper back.
:‫يستخدم هذا المكان فقط عند‬
- in dermatitis of forearm .
- children with small forearms.
Contraindications ‫ موانع استخدامه‬to skin prick
testing:
Do not apply skin prick tests to patients when there
is convincing history of anaphylaxis to the test
allergens.
this is particularly important in :
Nut ) ‫ جوز ( مكسرات‬allergy.
latex ‫ افرازات بعض النباتات‬allergy .
horse allergy.
drug allergy .
severe food allergy.
Other contraindications:
1.Diffuse dermatological condition. ‫عرض او مشكله‬
‫جلديه منتشره‬
2. Patient unable to stop medications .
( anti-histamines inhibit the wheal& flare reaction
patients advised to stop the drug 3-10 days before
skin testing ) ‫عشان ما يمنع هذا الدواء ظهور نتائج‬
‫االختبار‬
‫‪3. during pregnancy.‬‬
‫‪3. poor patient cooperation .‬‬
‫‪4 .Severe dermatographism‬‬
‫ارتيكيريا ناتجه عن مؤثر فيزيائي‬
‫مثل كثره الحك و الدخان ( مثل اللي يطلع‬
‫‪ .‬اذا لبست حرام )‪‬‬
Interpretation ‫ تفسير ميكانيكيه‬of the skin test .
Positive control skin test ( histamine )
Negative control skin test (diluent )
( essential for correct interpretation) .
-15 minutes after application of allergen,
examine test site for a wheal and flare .
- a positive reaction = a wheal 3 mm or greater
in diameter + erythema .
Selection of allergens for testing .
- There are over 400 allergens known to cause
allergic disease .
Selection is based on :
1.medical history .
2. prevalent ‫ المنتشره‬allergens in the area .
SPT is safe ,but the following
emergency resuscitative equipment must be
available :
* Injectable Adrenaline 1:1000. ‫االهم‬
* Oxygen .
* Oral Phenergan ‫& دواء مضاد للهستامين‬
injectable.
* Hydrocortisone .
* Inhaled bronchodilator.
Number of allergens and age:
* ‫ عدد المثيرات‬: Any number from 1-40 allergens may be tested
in a single session .
* ‫عمر االشخاص‬: Consensus ‫ االجماع ينص على أنه‬indicates that
the tests are of value from 4 months of age onwards .
However,
Infants & the elderly tend to have a less reactive
skin.
‫ االختبار الثاني‬Multi – test device:
‫ أوال‬: Dip ‫ غمس‬applicator in allergen tray ‫صينيه‬.
‫ ثم ثانيا‬: Apply with pressure on the arm.
a positive test:
= 4.5 mm. wheal diameter.
( preferred by patients.)
) ‫الحظ انه ال ينتج حمره ( احمرار‬
‫وان القطر اكبر من االختبار السابق‬
Correlation ‫ العالقه بين‬between :
* size of skin test.
* degree of IgE sensitization.
* clinical symptoms.
90 % of patients with a wheal = 5mm.
react positive on provocation ‫ اثاره‬tests & the
allergen
tested is involved in clinical
disease .
‫ االختبار الثالث‬:
Intradermal test :
used for investigating : ‫يستخدم‬
: ‫للكشف عن‬
1. insect sting allergy .
2. drug allergy .
*High non-specific reaction rate.
‫ االختبار الرابع‬: allergen - specific serum IgE test .
( also called RAST test – radioallergo-sorbent test )_
• Advantages:
1. No risk of reactions.
2. Not affected by medications.
3.Preferred in patients with high risk
of reactions:
-unstable asthma.
-anaphylaxis.
-sting insect allergy.
• Disadvantages :
1. Expensive.
2. Less sensitive than SPT.
3. Difficult to interpret ‫ الكشف‬in
patients with high level of total IgE (1000 KU/ml )
Specific IgE (RAST) results are reported in classes :
class o : no specific IgE detected.
class 1 : low level .
class 2-4 : moderate level .
class 5-6 : high level .
Total serum IgE.
The spread of total IgE values is very wide
and reliable upper limits distinguishing
non-atopic and atopic could not be
established .
* Useful in large epidemiologic studies.
* Not applicable in the clinical evaluation
of individual patients.
Conditions with elevated total IgE :
These may include :
1. certain immunodeficiency disorders .
2. parasitic infections .
3. certain types of T-cell lymphomas .
4. atopic dermatitis .
5. eosinophilic lung disease .
Positive skin test reactions with no symptoms affect
8-30 %
These reactions may indicate :
1. past sensitization .
2. latent ‫ الكامنه‬allergy .
.
Prospective ‫ سابقه‬studies in Denmark showed that
30 to 80 % ( of asymptomatic patients with positive skin
test become allergic depending on :
allergen exposure.
*have prognostic ( preventive) value.
Bodtger U; Current Opin Allergy Clin Immunl,2004;4(1):5-10.
Summary :
1. diagnosis of allergy determine line of
treatment e.g. avoidance of allergen,
immunotherapy .
2. skin test reactivity should be correlated ‫مربوط مع‬
with clinical sensitivity .
3. definitive diagnosis of food allergy is by
double-blind challenge tests . ‫مهمه‬
4. administration of allergy vaccines require
accurate identification of causative
allergens .(immunotherapy ).