過敏原試驗應用與判讀 台中榮民總醫院 過敏免疫風濕科 吳沂達醫師洪維廷醫師陳怡行醫師
學習目標 1. 了解過敏原理及其相對應症狀疾病 2. 能正確選擇及開立過敏原檢查 3. 能正確判讀過敏原檢查結果
Syllabus 甚麼是過敏 過敏之症狀及疾病 選擇適當過敏原檢查 判讀過敏原檢查結果 總結
身體對無致病性的蛋白質 產生免疫反應
Modified Coombs and Gell Classification of Allergic Reactions Kay, A.B. Allergy and Allergic Diseases 2008,3-22.
Syllabus 甚麼是過敏 過敏之症狀及疾病 選擇適當過敏原檢查 判讀過敏原檢查結果 總結
第一型過敏反應 ( 立即型 ) 皮膚發癢, 潮紅 蕁麻疹 / 血管性水腫 打噴涕 / 流清鼻水 / 鼻塞 眼睛癢 / 流眼淚 / 結膜充血水腫 支氣管攣縮, 氣喘發作 嘔吐, 腹部絞痛, 腹瀉 過敏性休克
The IgE-dependent allergic inflammation Initial exposure: sensitization IL 4 Th 2 IL 5 IL 13 B Ig E
The IgE-dependent allergic inflammation Initial exposure: sensitization Th 2 IL 4 IL 5 IL 13 Re-exposure: allergic reaction FceRI B Ig E Mast cells/basophils
第二型過敏反應 (cytotoxic) Allergen- specific IgG 或 IgM 作用在細胞上 溶血 白血球低下 血小板低下 Onset: 不一定
第三型過敏反應 免疫複合體在組織沉積, 引起補體活化及發炎反應 Serum sickness 發燒 皮疹 關節痛 血管炎 淋巴結腫大 腎絲球腎炎 Onset : Expose 過敏原 1-3 週後
第四型過敏反應 過敏性接觸性皮膚炎 固定性藥疹 Erythema multiforme Steven-Johnson syndrome Toxic epidermal necrolysis
常見過敏病 過敏性氣喘 過敏性鼻炎 / 過敏性結膜炎 異位性皮膚炎 過敏性休克 蕁麻疹 / 血管性水腫 過敏性接觸性皮膚炎 食物過敏 藥物過敏
Syllabus 甚麼是過敏 過敏之症狀及疾病 選擇適當過敏原檢查 判讀過敏原檢查結果 總結
做什麼檢查? In vivo test Prick-puncture test Intra-dermal skin test Inhalation challenge Oral challenge test Patch test In vitro test Allergen-specific IgE Phadia ImmunoCAP MAST Basophil histamine releasing test Basophil functional test (LTC4, surface marker) HLA B1502; B5801
以過敏病的免疫機轉來選定適 當的過敏檢查 疾病的免疫機轉 Laboratory tests Type I (IgE-mediated) Skin testing (eg. PST), Serum tryptase, Specific IgE Type II (IgG-mediated) Type III (immune complex) Type IV (delayed, cell mediated) Direct or indirect Coomb s test, ANA,anti-platelet Ab, antihistone Ab, AMA, AMiA, etc. ESR, CRP, CIC, C3, C4, CH 50, biopsy Patch test, tuberculin skin test, lymphocyte transformation test
過敏原皮膚試驗 Prick-prick test
過敏原皮膚試驗 Positive control (histamine 1mg/ml) Negative control (phosphate-buffered saline) Allergen : 20 分鐘後判讀
RAST RAST 1 st on the market in 1974, considerable variability & questionable quantification-no longer in use and term is no longer appropriate
Allergen Specific IgE Test
MAST Multiple allergy-simultaneous test
Comparison ImmunoCAP MAST Coating Cellulose sponge (3D) Allergen number 6 36 Sample per test 40uL 1.3ml Paper disc/cellulose thread (2D) 40uL*6=240uL plasma 240uL*3=720uL=0.72ml whole blood
Limitation Not golden standard False positive due to non-specific binding Levels of specific IgE depend on age, allergen specificity, total serum IgE, season of year (for inhalant allergens) Cost Delay of time acquiring results
When to choose Inhalant allergens Perennial: indoor Seasonal: outdoor Smoking, perfume, air pollutant Asthma/AR/AD/ana phylaxis Food allergen Screening 50% false positive False negative SPT prick-prick test Urticaria/AD/Anaph ylaxis Food additives? Food intolerance?
Significance Of Positive Allergy Skin Test Results Food Allergy Diagnostic Testing Pearls, Pitfalls and the Gold Standard Allergy tests yield information on sensitization, which is not always equivalent to clinical allergy. Neither skin or serum sige have 100% sensitivity or specificity The double-blind, placebo-controlled food challenge is the gold standard for food allergies but it is a time-consuming procedure that is limited to trained allergy specialists and 26 carries the risk of producing a severe reaction
過敏原貼布試驗 Patch test
疾病的免疫機轉 Type I (IgE-mediated) Type II (IgG-mediated) Type III (immune complex) Type IV (delayed, cell mediated) Laboratory tests Skin testing (eg. PST), Serum tryptase, Specific IgE Direct or indirect Coomb s test, ANA,anti-platelet Ab, anti-histone Ab, AMA, AMiA, etc. ESR, CRP, CIC, C3, C4, CH 50, biopsy Patch test, tuberculin skin test, lymphocyte transformation test
Syllabus 甚麼是過敏 過敏之症狀及疾病 選擇適當過敏原檢查 判讀過敏原檢查結果 總結
Skin Prick Test Grade (-) Size (mm x mm) 1+ > Negative control 3mm but <1/2 positive control 2+ ½ but< positive control 3+ =size of positive control ±1mm 2 4+ >positive control with pseudopods
Sensitization Reaction
In Vitro Tests Semiquantitative classes I-IV or VI Class I and class II: allergen sensitization Classes V and VI: correlate with IgEmediated clinical reactions Latex: Nonzero=positive
In Vitro Tests
In Vitro Tests Some cross-reactivity may result in clinically irrelevant positive tests Mites, crab, shrimp (avoidance not necessary) Results do not predict severity
Molecular allergen test
Diagnostic Algorithm
Syllabus 甚麼是過敏 第一型過敏之症狀及疾病 選擇適當過敏原檢查 判讀過敏原檢查結果 總結
Summary Specific IgE levels higher than 0.35 ku/l suggest sensitization, but that is not synonymous with clinical disease The sensitivity of allergy blood tests ranges from 60%-95%, and the specificity ranges from 30%-95% Neither allergy blood testing nor skin testing should be used for screening
Thank You Questions and Comments
Allergy Skin Testing Advantages & Diagnostic Utility in Comparison to Specific- IgE Antibody SPT may be more sensitive in predicting who will react on challenge In pts with low food sige, SPT may have diagnostic utility SPT can identify sensitivity to labile food proteins
Systemic reactions to allergy skin tests Method: Retrospective study at the Mayo Clinic to identify patients who developed systemic reactions to skin tests Results:. 497,656 skin tests were performed : SPT 16,505 patients 6 patients experienced SRs. All had asthma. SPT SR rate was 15 or 23 reactions per 100,000 aeroallergen tests It is noteworthy that there were no systemic reactions to skin tests for foods or venoms Conclusion: SR to skin tests was very low. SRs were mild and all patients recovered fully within 1 hour. 45 Valyasevi et al, Ann Allergy Asthma Immunol 1999;83:132 136.
Why Skin Testing is Superior to In Vivo Testing Because: More cost and time efficient for patient Results available on initial consultation allowed for development of specific treatment plan Predictive value in terms of presence of clinical allergy and possible severity In some cases greater predictive value than in vivo test Ability to test to allergens that may be altered in extract preparation process e.g., natural foods Can also be used in component-resolved diagnosis