Clinico Pathological Test SCPA605-Essential Pathology

Clinico Pathological Test SCPA605-Essential Pathology Somphong Narkpinit, M.D. Department of Pathogbiology, Faculty of Science, Mahidol University e-mail : somphong.nar@mahidol.ac.th

Pathogenesis of allergic dermatitis (ACD) and urticaria

Pathogenesis ACD ACD => delayed type hypersensitivity Process of sensitization can be divided into Sensitization phase Elicitation phase

http://www.hse.gov.uk/skin/professional/causes/dermatitis.htm

Contact Urticaria type I

Diagnosis tests for Contact Urticaria Radioallergosorbant test (RAST) Open application Occlusive application (Patch/chamber test) Prick, scratch or intradermal testing The precautions for the treatment of anaphylaxis must be maintained.

Pathogenesis ACD Immunologic Response Hypersensitivity Type 4 Non-Immunologic Response Test - Close Patch test ICD - + - R/O ACD Photo ACD Type 4 - Photo Patch Test Photo Toxic CD - + R/O Photo ACD Contact Urticaria Type 1 + Prick test

Diagnosis

Diagnosis History Taking Onset, course, off-on, occupation Underlying disease : Atopic/allergy Past history Medication Use Physical Examination Special Test

Physical Examinaton

Patch Test

Planing for Patch Testing Indication Contraindication The patch test unit Selecting test substances Concentration of the test substance Vehicle Instruction of patient Application of the test patch Reading of the result Risk by testing

Indication for Patch Testing Suspected allergic contact dermatitis Hand dermatitis Atopic dermatitis Seborrheic dermatitis Nummular dermatitis Stasis dermatitis Lichenoid dermatitis

Contra-indication for Patch Testing Avoid using TEST in patients with extensive ongoing outbreaks of contact dermatitis: In these patients, patch testing can elicit intense reactions at current and previously affected sites, and false positive results could be obtained.

Precaution TEST should only be applied to healthy skin: The safety and efficacy of TEST patch testing in children is unknown: Test sites should be free of scars, acne, dermatitis, hair, or other conditions that may interfere with test result interpretation. Avoid patient use of immunosuppressants and immunomodulators prior to and during testing: 6 months to 14 years of age, and positive reactions occurred at rates similar to previously published pediatric studies that used conventional patch testing. The safety and efficacy of TEST patch testing in women who are pregnant or breast-feeding is unknown: No adequate and well-controlled trials Oral steroids (>10 mg of prednisolone) may suppress positive TEST & the risk of false negative => avoided for 2 weeks. oral antihistamine use before and during TEST patch testing it is not advised, due to the risk of suboptimal result Topical steroids, antihistamines and other immunosuppressants (e.g., tacrolimus) may be used on non-test areas, but should be avoided on potential patch test areas prior to and during testing. Keep TEST panels dry during testing: Patients should avoid activities that cause excess perspiration or expose the test area to excess moisture. Sponge baths are acceptable provided the patient protects the panels and surrounding skin from excess moisture.

Material Test material : Standard Allergen International Contact Dermatitis Research Group(ICDR) North American Contact Dermatitis Research Group(NACDR) Non standard Allergen Test area : Inter-scapular, Upper arm Test time : >48hrs

Standard Allergen 1. metal 2. cosmetics 3. medication 4. rubber

Preparing standard patch test

Preparing standard patch test

Preparing standard patch test

Preparing standard patch test

Preparing standard patch test

Preparing standard patch test

Preparing standard patch test

Testing to non-standard antigens

Testing to Nonstandard Antigens (1) PRODUCT Cosmetics and personal care products Leave on : Base makeup moisturizer Eye cosmetics nail polish lipsticks Sunscreens, colognes perfumes TEST CONC. AS is Wash off Soap shampoo cream 1:100 to 1:10 dilution Household products: Detergents, Bleach solvents cleansers 1:100 to 1:1000 dilution

Testing to Nonstandard Antigens (2) PRODUCT TEST CONC. Tropical medications Antibacterials eye and preparation As is corticosteroids Exception: Wart products, anthralin, 1:10 to 1:1000 benzoyl peroxide, tretinoin (Retin-A)

Testing to Nonstandard Antigens (3) PRODUCT Industrial products Clothing, shoes, plants TEST CONC. With care, always use material safety data sheets to determine the dilution As is, and soaked with saline or water for 10 mins. Leave in place for 96 hrs.

Avoiding Irritant Tests Test only skin that appears completely normal Avoid concentrations of patch test materials that are irritating Do not prepare the skin by cleansing it with soaps or solvents Avoid patch testing with materials other than the standard series to minimize irritant reactions. Seek consultation for testing with nonstandard substances.

Adverse Reaction to Patient Alteration in pigmentation Persistance of reaction Temporary flare of dermatitis Active sensitization Anaphylactiod reaction Koebner phenomenon Ectopic flare of dermatitis Necrosis scarring and keloids fisher s cd. 5 th ed. Marks JG contact & Occ. Derm 3 rd ed.

Recording of Test Reaction? Doubtful reaction faint macular erythema + weak (nonvesicular) positive reaction: erythema, infiltration, papules ++ strong (vesicular) posotive reaction erythema, infiltration, papules, vesicles +++ extreme positive reaction; bullous - Negative reaction IR irritant reaction of different types NT Not Tested

Validity of Patch Testing Results The validity of any test system is its intrinsic ability to detect which individuals have the target disease and which do not, relying on the test capability to detect both true positive and true negative reactions, while minimizing the number of falsepositive and false-negative reactions.

Relevance of positive reactions An assessment should be made of the relevance of each positive reaction to the patient s presenting dermatitis. A simple and pragmatic way of classifying clinical relevance of positive allergic patch test reactions is: (i) current relevance the patient has been exposed to allergen during the current episode of dermatitis and improves when the exposure ceases; (ii) past relevance past episode of dermatitis from exposure to allergen; (iii) relevance not known not sure if exposure is current or old; (iv) cross reaction the positive test is due to cross-reaction with another allergen; (v) exposed a history of exposure but not resulting in dermatitis from that exposure, or no history of exposure but a definite positive allergic patch test.

False Positive Reactions Too high concentration The test substance is contaminated by an irritant The vehicle of the test substance Application on the wrong test area Strong reaction to the adhesive tape Eczema in acute phase present Eczema present near the test site Pressure effect of solid material Reading is made too early

False Negative Reaction Too low concentration Inappropriate vehicle Delayed reactivity Duration of contact that is too brief Loosed or wet patches Influence of corticosteroids Reading is made too early

Method & procedure of Patch Test

1. TAKE PATIENT HISTORY AND PERFORM PHYSICAL EXAM A complete and accurate history is essential. Ask about: Symptoms (duration and distribution) Personal and family history of allergies Exposure to materials or products at work and at home. PE : Examine the patient at a level appropriate to case complexity. Chronic, persistent dermatitis with characteristics indicative of a contact allergy should be evaluated with patch testing.

2. SCHEDULE PATIENT AND PROVIDE PRE-TEST INSTRUCTIONS In patients with severe ongoing dermatitis, avoid patch testing until acute symptoms subside to avoid eliciting excited skin syndrome and false positives. Drug : Two weeks prior to patch testing stop using oral corticosteroids and avoid use of topical corticosteroids on the test area. Activities : Do not expose the test area to sun for at >3 weeks prior to testing. Test area should be clean and free of oils, lotions and ointments. Select an area : without scars, active dermatitis, skin eruptions or any other condition that may interfere with test interpretation. Coordinate with patient schedules for best compliance.

3. APPLY THE TEST

4. REMOVE TEST AT 48 HOURS; INTERPRET RESULTS AT 72 AND 96 HOURS Interpret 48-hour reactions after allowing them to subside for a few minutes. Recall patient at 72 96 hours for additional readings. A second reading is essential to reduce false positive and false negative results. Additional readings may be required depending on patient history and results.

INTERPRETING AND RECORDING REACTIONS TO T.R.U.E. TEST ALLERGENS

INTERPRETING AND RECORDING REACTIONS TO T.R.U.E. TEST ALLERGENS

5. COUNSEL THE PATIENT With positive reactions of clinical relevance, counsel patients to avoid each allergen. How to Read a Label as well as the appropriate patient handouts with information about: where each allergen is found at work and home; How to avoid each allergen; substances (with their chemical names) to avoid Examples of products that contain the allergen, with potential alternative products.

The provocative use test and open test

The Provocative Use Test Valuable in testing for non irritating substance Suspected material apply 3 cm³ area twice daily ; for 1 wk. (not wash) Normal skin (anticubital fossa) Previous sensitized skin No reaction negative False negative reaction are common

The open patch test is commonly used where potential irritants or sensitizers are being assessed. It is also useful in the investigation of contact urticaria and protein contact dermatitis. Apply : 1 cm³ bid for 2-3ds The open patch test is usually performed on the forearm area the upper outer arm area Scapular area Results CLOSE OPEN RESULTS + + ICD + - ACD - + ICD

A repeated open application test (ROAT) Applying The suspect agent on to the forearm, is also useful in the assessment of cosmetics, where irritancy or combination effects may interfere with standard patch testing. This usually involves application of the product twice daily for up to a week, stopping if a reaction develops.

Treatment of CD Find the causes

Treatment Topical, systemic steroids Calcineurin inhibitors Sedating antihistamines Remember: No treatment works very well as long as allergen exposure is continuing

Prevention Find the causes