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Diagnosis of type 1 allergy.

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Presentation on theme: "Diagnosis of type 1 allergy."— Presentation transcript:

1 Diagnosis of type 1 allergy.
Prof. Mohamed Osman Gad ElRab . College of Medicine & KKUH .

2 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 ).

3 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 .

4 Major indications دواعي الاستخدام الاساسيه for allergy testing .

5 are not controlled by medications .
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.

6 Prevalence معدل الانتشار :
60 – 70 % of rhinitis patients have allergy ( IgE- mediated ). 25 – 34 % of patients with rhinitis develop asthma within 10 years .

7 2. patients with persistent دائم symptoms of asthma .
58-80% of asthma patients have immediate skin test reactivity . .(Kalliel etal. Chest 1989,96: ). 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: ).

8 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 ,Bethesda,Md.,1997: 43,45

9 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 .

10 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 ) .

11 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 .

12 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 )

13 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 .

14 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

15 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

16 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 .

17 Site for prick test اماكن الوخز :
The inner (volar الراحه ( 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.

18 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.

19 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

20 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 ) .

21 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 .

22 Selection of allergens for testing
Selection of allergens for testing There are over 400 allergens known to cause allergic disease Selection is based on : medical history prevalent المنتشره allergens in the area .

23 SPT is safe ,but the following emergency resuscitative equipment must be available :
* Injectable Adrenaline 1:1000. الاهم * Oxygen . * Oral Phenergan دواء مضاد للهستامين & injectable. * Hydrocortisone . * Inhaled bronchodilator.

24 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.

25 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

26 Correlation العلاقه بين between :. size of skin test
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 .

27 *High non-specific reaction rate.
: الاختبار الثالث Intradermal test : used for investigating : يستخدم للكشف عن : insect sting allergy drug allergy hg *High non-specific reaction rate.

28

29 2. Not affected by medications. 3.Preferred in patients with high risk
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.

30 1. Expensive. Disadvantages : 2. Less sensitive than SPT.
3. Difficult to interpret الكشف in patients with high level of total IgE (1000 KU/ml )

31

32 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 .

33 The spread of total IgE values is very wide
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.

34 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 .

35 Positive skin test reactions with no symptoms affect 8-30 %
These reactions may indicate : 1. past sensitization . 2. latent الكامنه allergy . .

36 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.

37 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 .

38 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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