Atopy patch test with different vehicles and allergen concentrations: an approach to standardization

Area of Science:

• Dermatology
• Allergology
• Immunology

Background:

• Eczematous skin lesions in atopic eczema can be triggered by patch testing with aeroallergens.
• Standardization of the atopy patch test (APT) is crucial for accurate diagnosis.

Purpose of the Study:

• To establish a standardized system for the atopy patch test (APT).
• To evaluate the efficacy of different allergen concentrations and vehicles for APT.

Main Methods:

• 36 patients with atopic eczema, 4 with rhinoconjunctivitis, and 10 controls underwent epicutaneous testing.
• Allergen extracts (house dust mite, cat dander, grass pollen) were applied at 1000 and 10,000 PNU/gm in petrolatum or hydrogel.
• Reactions were assessed at 48 and 72 hours and compared with skin prick and specific serum IgE tests.

Main Results:

• 57 positive APT reactions were observed in patients with atopic eczema, primarily at higher allergen concentrations (10,000 PNU/gm) and with petrolatum vehicle.
• Concordance with skin prick tests and CAP-RAST varied between 0.39-0.69.
• No positive reactions were seen in healthy controls or patients without atopic eczema.

Conclusions:

• Petrolatum vehicle and allergen concentrations above 1000 PNU/gm enhance APT results on intact skin.
• APT shows potential for evaluating the clinical relevance of IgE-mediated sensitization in eczematous skin lesions.