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Introduction :
Many patients with various مختلفه clinical
problems are suspected to have an allergic disease , يعني
حساسيه عنده انه اعتباراتك من مريضحط جاك اذاهم المرضى هذوال : واغلب
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 :
الحساسيه عالج انواع : اشهر - allergen avoidance مثيرات تجنب. الحساسيه
- medications .
- immunotherapy .
1. patients with rhinitis in whom symptoms
are not controlled by medications .
allergic rhinitis .( IgE- mediated ). ( اللي هو النوع هذاللعالجات يستجيب ما اللي هو النوع وهذا االختبار بعمل عنه نبحث( العاديه
non-allergic rhinitis .( non IgE- mediated ) .
infectious . aspirin hypersensitivity. non-specific.
Prevalence االنتشار : معدل
60 – 70 % of rhinitis patients have
allergy ( IgE- mediated ).
25 – 34 % of patients with rhinitis develop
asthma within 10 years .
2. patients with persistent دائم symptoms 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 مساهمه factors .
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
حليب مع مشاكل يواجهون اللي الناس بعض مثل الطعام تحملياااي ( ) الجمالت
- 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 الرئيسي : of therapy remains الدعم
1. avoidance of the incriminated المسببالفول ( ) من الناسحساسين بعض .foods للحساسيه
2. education to deal with inadvertent exposure اكل ( اكل واحد المفاجئه الحاالت مع للتعامل التعليمحساسيه ) يسبب انه درى . ما
4. patients with suspected drug allergy .
- reliable ودقيق allergy tests for drugs are فعالavailable only for penicillin and local anesthetics
الموضعي جدا . التخدير مهمه
- e.g. suspected reaction to penicillin .
prescribe له مضاد alternative antibiotic يوصفآخر . حيوي
5. suspected insect sting reactions :
previous suspected systemic reaction to insect stings . - identify insect . - advice immunotherapy. من الحشرات الن
على ( مب يعني بها التحكم يمكن ال التي الحساسيه مثيراتحشرات تاكل ما ( كيفك
- e.g. the honey bee & black fire ant are common causes of anaphylaxis.
بـ وتعالج للوفاه تؤدي ان الممكن من والتي المفرطه الحساسيهEpinephrine ( 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 قياس for allergen specific IgE antibodies .
3. Bronchial challenge test .
( occupational asthma المفتعل ( الربو - expose patient to allergen and record symptoms.
4. Double- blind food challenge test .
provide definitive النهائي diagnosis of food allergy
when clinical certainty والتاكيد . is needed االعتماد
( 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 .
نتائج تعطي
Principle المبادئ of 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 الوخز : اماكن
• The inner (volar ( ) الباطن aspect of the (الراحهforearm.
Or :
The skin of the upper back.
عند فقط المكان هذا :يستخدم - in dermatitis of forearm .
- children with small forearms.
Contraindications استخدامه to skin prick موانعtesting:
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 ( ) مكسرات .allergy جوز
latex النباتات بعض . allergy افرازات
horse allergy.
drug allergy .
severe food allergy.
1.Diffuse dermatological condition. او عرضمنتشره جلديه مشكله
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 ) ظهور الدواء هذا يمنع ما عشان
االختبار نتائج
Other contraindications:
3. during pregnancy.
3. poor patient cooperation .
4 .Severe dermatographism
فيزيائي مؤثر عن ناتجه ارتيكيريايطلع ( اللي مثل الدخان و الحك كثره مثل
حرام لبست . ( اذا
Interpretation ميكانيكيه . of the skin test تفسير
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 المنتشره allergens in the area .
SPT is safe ,but the followingemergency resuscitative equipment must be
available :
* Injectable Adrenaline 1:1000. االهم * Oxygen .
* Oral Phenergan للهستامين مضاد & دواءinjectable.
* Hydrocortisone .
* Inhaled bronchodilator.
Number of allergens and age:
المثيرات * Any number from 1-40 allergens may be : عدد
tested in a single session .
* االشخاص أنه Consensus : عمر على ينص indicates االجماع
that the tests are of value from 4 months of age onwards .
However,
Infants & the elderly tend to have a less reactive skin.
الثاني :Multi – test device االختبار
.صينيه applicator in allergen tray غمس Dipأوال :
ثانيا : .Apply with pressure on the arm ثم
a positive test:
= 4.5 mm. wheal diameter.
( preferred by patients.)
احمرار ( ) حمره ينتج ال انه الحظ
السابق االختبار من اكبر القطر وان
Correlation بين : between العالقه
* size of skin test. * degree of IgE sensitization. * clinical symptoms.
90 % of patients with a wheal = 5mm.
react positive on provocation اثاره tests & the allergen tested is involved in clinical disease .
الثالث : : Intradermal test االختبار
used for investigating : يستخدمعن : للكشف
1 . insect sting allergy . 2. drug allergy .
hg
*High non-specific reaction rate.
الرابع . allergen - specific serum IgE test : االختبار ( 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 الكشف in 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 الكامنه allergy .
.
Prospective سابقه studies 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 مربوطمع
with clinical sensitivity .