Patch Test presentation

1. patch tests
By : Muhammed Abdulaziz Alghurery

2. PATCH TEST
• Used for diagnosis of allergic contact
dermatitis
• Basis of the testing is to elicit an immune
response by challenging already sensitized
persons to defined amount of allergen and
assessing the degree of response

3. INDICATIONS FOR PATCH TESTING
 Eczematous disorders where contact allergy
is suspected or to be excluded
 Eczematous disorders failing to respond to
treatment as expected
 Chronic hand and foot eczema
 Persistent or intermittent eczema of face,
eyelids, ear and perineum
 Varicose eczema

4. PATCH TEST MATERIALS
• Finn Chamber
• Aluminium - 8 mm diameter & 0.5 mm depth
• Tight apposition
Patch Test Units
Tapes
• Non – allergenic
• Non - Irritant
Vehicles
Allergens
• Petrolatum
• Suitable concentration
• Stored properly

5. PATCH TEST PROCEDURE
0 hours
Antigens applied
0 hours
Occluded
immediately
48 hours
Occlusion removed
48 hours
Reading after half
an hour
96 hours
Reading at 96
hours

6. PATCH TEST GRADING
GRADING DESCRIPTION PICTURE INTERPRETATION
- No erythema orpapules Negative
+/-or ? Erythemaonly Doubtful Positive
+ Erythema, mild infiltration,
discrete papules
WeakPositive
++ Erythema, infiltration, papules
and vesicles
Strong Positive
+++ Intense erythema, coalescingvesicles Extreme Positive
IR Sharply demarcated erythema
or epidermal necrosis
Irritant reaction
NT Not Tested

7. FALSE POSITIVE AND FALSE NEGATIVE
FALSE POSITIVE PATCH TEST
 Wrong Test Substance
 Excited Skin Syndrome/Angry back Syndrome/Status eczematicus –
Occurs in patients presenting with multiple concomitant positive reactions
to diagnostic patch tests for ACD in whom a single repeated challenge
reveals some of them to be non reproducible
 Artifact
FALSE NEGATIVE PATCH TEST
 Insufficient amount
 Non occlusion
 Corticosteroids
 Refractory state

8. THANK
YOU