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Diagnosis of type 1 allergy. PowerPoint PPT Presentation


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Diagnosis of type 1 allergy. Prof. Mohamed Osman Gad ElRab . College of Medicine & KKUH . Introduction :. Many patients with various مختلفه clinical problems

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Diagnosis of type 1 allergy l.jpg

Diagnosis of type 1 allergy.

Prof. Mohamed Osman Gad ElRab .

College of Medicine & KKUH .


Introduction l.jpg

Introduction :

Many patients with various مختلفه clinical problems

are suspected to have an allergic disease , يعني اذا جاك مريض حط من اعتباراتك انه عنده حساسيه واغلب هذولا المرضى هم :

e.g. . - itching skin rashes.

- upper & lower respiratory symptoms .

- adverse reactions to food .

- adverse reactions to drugs,(antibiotics,

local anesthetics, analgesics ).


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  • Establishing a correct allergy diagnosis help to

    select appropriate therapeutic interventions for

    the patient such as :

    اشهر انواع علاج الحساسيه :

    - allergen avoidance تجنب مثيرات الحساسيه .

    - medications .

    - immunotherapy .


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Major indications دواعي الاستخدام الاساسيه for allergy testing .


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  • 1. patients with rhinitis in whom symptoms

  • are not controlled by medications .

  • allergic rhinitis .( IgE- mediated ). ( هذا النوع هو اللي نبحث عنه بعمل الاختبار وهذا النوع هو اللي ما يستجيب للعلاجات العاديه )

  • non-allergic rhinitis .( non IgE- mediated ) .

  • infectious . aspirin hypersensitivity. non-specific.


Prevalence l.jpg

Prevalence معدل الانتشار :

60 – 70 % of rhinitis patients have

allergy ( IgE- mediated ).

25 – 34 % of patients with rhinitis develop

asthma within 10 years .


2 patients with persistent symptoms of asthma l.jpg

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 ).


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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 l.jpg

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 الجملات ( 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 of therapy remains l.jpg

Diagnosis of food allergy is important because the mainstay الدعم الرئيسي of therapy remains :

1. avoidance of the incriminated المسبب للحساسيه ( بعض الناس حساسين من الفول ) foods.

2. education to deal with inadvertent exposure التعليم للتعامل مع الحالات المفاجئه ( واحد اكل اكل ما درى انه يسبب حساسيه ) .


4 patients with suspected drug allergy l.jpg

4. patients with suspected drug allergy .

- reliable فعال ودقيق allergy tests for drugs are available only for penicillin and local anesthetics التخدير الموضعي. مهمه جدا

- e.g. suspected reaction to penicillin .

prescribe يوصف له alternative antibiotic مضاد حيوي آخر .


5 suspected insect sting reactions l.jpg

5. suspected insect sting reactions :

previous suspected systemic reaction to insect

stings .

- identify insect .

- advice immunotherapy. لان الحشرات من

مثيرات الحساسيه التي لا 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 l.jpg

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 .


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3. Bronchial challenge test .

( occupational asthma الربو المفتعل )

- expose patient to allergen and record symptoms.

4.Double- blind food challenge test .

provide definitive النهائي diagnosis of food allergy

when clinical certainty الاعتماد والتاكيد is 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 l.jpg

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 of the skin test l.jpg

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 l.jpg

Site for prick test اماكن الوخز :

  • The inner (volarالراحه ( الباطن )) aspect of the forearm.

    Or :

    The skin of the upper back.

    يستخدم هذا المكان فقط عند:

    - in dermatitis of forearm .

    - children with small forearms.


Contraindications to skin prick testing l.jpg

Contraindications موانع استخدامه to 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 ( مكسرات ) allergy.

latex افرازات بعض النباتات allergy .

horse allergy.

drug allergy .

severe food allergy.


Other contraindications l.jpg

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 الاختبار


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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 of the skin test l.jpg

Interpretation تفسير ميكانيكيه of 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 .


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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 following emergency resuscitative equipment must be available l.jpg

SPT is safe ,but the followingemergency resuscitative equipment must be available :

* Injectable Adrenaline 1:1000. الاهم

* Oxygen .

* Oral Phenergan دواء مضاد للهستامين & injectable.

* Hydrocortisone .

* Inhaled bronchodilator.


Number of allergens and age l.jpg

Number of allergens and age:

* عدد المثيرات : Any number from 1-40 allergens may be tested

in a single session .

*عمر الاشخاص : Consensus الاجماع ينص على أنه indicates that the tests are of value from 4 months of age onwards .

However,

Infants & the elderly tend to have a less reactive skin.


Multi test device l.jpg

الاختبار الثاني Multi – test device:

: أولاDip غمس applicator in allergen tray صينيه.

: ثم ثانيا Apply with pressure on the arm.

a positive test:

= 4.5 mm. wheal diameter.

( preferred by patients.)

لاحظ انه لا ينتج حمره ( احمرار )

وان القطر اكبر من الاختبار السابق


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Correlation العلاقه بين between : * 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 .


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: الاختبار الثالث Intradermal test : used for investigating : يستخدم للكشف عن : 1. insect sting allergy . 2. drug allergy .hg

  • *High non-specific reaction rate.


Allergen specific serum ige test also called rast test radioallergo sorbent test l.jpg

الاختبار 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.


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  • 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 l.jpg

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 l.jpg

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 l.jpg

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 l.jpg

Positive skin test reactions with no symptoms affect 8-30 %

These reactions may indicate :

1. past sensitization .

2. latent الكامنه allergy .

.


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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 l.jpg

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 .


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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 ).


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