Diagnosis of type 1 allergy.

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. 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 1989,96:1336-40). 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 ).

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.98-4051,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 (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.

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 . - There are over 400 allergens known to cause allergic disease . Selection is based on : 1.medical history . 2. prevalent المنتشره allergens in the area .

23. 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.

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. * 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. : الاختبار الثالث Intradermal test : used for investigating : يستخدم للكشف عن : 1. insect sting allergy . 2. drug allergy .hg • *High non-specific reaction rate.

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

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. 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 ).