Reliability of skin test results when read at different time points

Area of Science:

• Allergy and Immunology
• Dermatology
• Clinical Diagnostics

Background:

• Standard practice for percutaneous skin testing involves reading wheal and flare reactions 15-20 minutes after allergen application.
• Clinical demands, such as emergencies or other patient care duties, can delay the timely reading of skin tests.
• The impact of delayed readings on the clinical significance and reliability of allergy skin tests requires investigation.

Purpose of the Study:

• To evaluate the reliability of skin-prick testing (SPT) results when read at extended time points (10, 30, and 40 minutes) compared to the standard 20 minutes.
• To determine if prolonged intervals between skin test application and reading affect the clinical significance of allergy diagnoses.
• To assess the optimal reading window for SPTs in routine allergy evaluations.

Main Methods:

• Fifty-three subjects with allergy symptoms underwent routine aeroallergen skin-prick testing.
• Reactions to allergen extracts, histamine (positive control), and a negative control solution were assessed.
• Wheal and flare reactions were measured at 10, 20, 30, and 40 minutes post-application.

Main Results:

• Skin-prick tests can be read up to 40 minutes after placement with acceptable results.
• The highest reliability for clinical significance was observed when tests were read between 20 and 30 minutes.
• Reading skin tests up to 30 minutes post-application showed no significant loss of reliability for diagnosing IgE-mediated hypersensitivity.

Conclusions:

• Delayed readings of allergy skin-prick tests are feasible, extending up to 40 minutes.
• Optimal reliability for allergy diagnosis is achieved with readings between 20 and 30 minutes.
• Immediate hypersensitivity skin testing remains reliable when read within 30 minutes.