Scratch-patch and patch testing in drug allergy--an assessment of specificity

Area of Science:

• Dermatology
• Clinical Pharmacology

Background:

• Adverse drug reactions (ADRs) are common but difficult to diagnose due to a lack of standardized identification procedures.
• Identifying the specific drug causing an ADR is challenging in clinical practice.

Purpose of the Study:

• To prospectively evaluate and compare scratch-patch and patch tests for frequently used drugs.
• To determine non-irritating concentrations of drugs for diagnostic testing.
• To assess the efficacy of these tests in identifying sensitized individuals.

Main Methods:

• 23 drugs (antibiotics, analgesics) were tested on 61 healthy individuals (non-exposed and exposed groups).
• Scratch-patch and patch tests were performed on the upper back using freshly prepared drug solutions.
• Tests were read at 24, 48, and 72 hours; 73 allergic individuals were included to validate test sensitivity.

Main Results:

• Identified non-irritating concentrations for 23 drugs, minimizing irritant reactions (IR).
• Four drugs (cefuroxim, acetylsalicylic acid, propyphenazone/drofenin-HCl, celecoxib) were most frequently associated with IR.
• Using petrolatum as a solvent reduced IR compared to PBS for certain drugs.

Conclusions:

• Established suitable drug concentrations for scratch-patch and patch tests that do not cause IR.
• Demonstrated the tests' ability to identify sensitized individuals, with 14 preparations eliciting positive reactions.
• Scratch-patch tests are a viable alternative to patch tests, offering earlier evaluation without increased irritation.