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Skin tests in the diagnosis of eruptions caused by betalactams
P Lisi1, V Lapomarda, L Stingeni
1Department of Medical and Surgical Specialities, University of Perugia, Italy.
Abstract:
The aetiologic evaluation of adverse cutaneous reactions to penicillins is still not an easy problem to solve. Skin testing is usually carried out intradermally with benzylpenicilloyl polylysine (BPO-PPL) and minor determinant mixture (MDM), but these are often unsuitable for the detection of sensitivity to betalactam antibiotics. 101 selected subjects, with different cutaneous reactions to betalactams and with a clinical history of positive challenge, were skin tested (patch test, prick test, intradermal test) with a standard betalactam series (amoxycillin, sodium penicillin G, ampicillin, bacampicillin, aztreonam, ceftriazone, BPO-PPL, MDM). 1 or more positive reactions to skin tests, mainly to intradermal tests, were observed in 47.5% of the subjects studied, especially in those with maculopapular eruptions, urticaria/angioedema and drug reactions caused by ampicillin and amoxycillin. Cross-sensitivity was demonstrated in 22.8% of cases and was due almost solely to the semisynthetic penicillins. Finally, to increase the yield in detecting positive patients, it is necessary that ampicillin and amoxycillin be tested in addition to major and minor determinants.
Insights
Diagnosing penicillin allergies requires improved skin testing. Adding ampicillin and amoxycillin to standard tests increases detection rates for adverse cutaneous reactions to betalactam antibiotics.
Area of Science:
- Pharmacology
- Dermatology
- Immunology
Background:
- Evaluating adverse cutaneous reactions to penicillins is challenging.
- Standard skin tests like benzylpenicilloyl polylysine (BPO-PPL) and minor determinant mixture (MDM) are often insufficient for detecting betalactam antibiotic sensitivity.
Purpose of the Study:
- To assess the efficacy of a standard betalactam series for skin testing in patients with cutaneous reactions.
- To determine the diagnostic yield of different skin tests and identify key allergens.
Main Methods:
- 101 subjects with a history of positive challenge and cutaneous reactions to betalactams underwent skin testing.
- Tests included patch, prick, and intradermal tests using amoxycillin, sodium penicillin G, ampicillin, bacampicillin, aztreonam, ceftriazone, BPO-PPL, and MDM.
Main Results:
- Positive skin test reactions were observed in 47.5% of subjects, primarily with intradermal tests.
- Ampicillin and amoxycillin were frequently implicated in reactions, particularly maculopapular eruptions and urticaria/angioedema.
- Cross-sensitivity was noted in 22.8% of cases, mainly among semisynthetic penicillins.
Conclusions:
- Current skin testing methods for penicillin allergy may be inadequate.
- Including ampicillin and amoxycillin in skin testing protocols is crucial for improving the detection of hypersensitivity to betalactam antibiotics.