Skin testing to detect penicillin allergy.

Area of Science:

• Immunology
• Allergy and Clinical Immunology
• Pharmacology

Background:

• A significant proportion of patients reporting beta-lactam antibiotic allergies exhibit positive skin test results.
• The prevalence of positive skin tests for penicillin allergy diminishes over time following a clinical reaction.

Purpose of the Study:

• To evaluate the efficacy and safety of skin testing with penicillin G (Pen G), penicilloic acid (PA), and penicilloyl poly-L-lysine (PPL) for diagnosing penicillin allergy.
• To assess the correlation between positive skin test results and factors such as time elapsed since reaction and patient age.

Main Methods:

• Conducted skin testing on 740 subjects with a history of apparent allergic reactions to beta-lactam antibiotics.
• Utilized penicillin G (Pen G), penicilloic acid (PA), and penicilloyl poly-L-lysine (PPL) for skin testing.
• Assessed results from epidemiologic and immunologic perspectives, noting reactions to other beta-lactam antibiotics.

Main Results:

• 63% of subjects with a history of penicillin allergy were skin-test positive.
• Positive skin test prevalence decreased significantly with time elapsed since the initial reaction (93% at 7-12 months vs. 22% at ≥10 years).
• Testing with PPL, PA, and Pen G identified 76.3% of positive patients; omitting any single agent would have missed a notable percentage of positive reactors.

Conclusions:

• Skin testing with PPL, PA, and Pen G is a rapid, safe, and effective diagnostic tool for identifying patients at risk for penicillin allergy.
• Skin test results are influenced by the time since the last allergic reaction and patient age.
• Skin testing did not provoke serious allergic reactions, and negative reactors tolerated subsequent beta-lactam antibiotic therapy well.