Skin tests in the diagnosis of betalactam allergy

Abstract

The sensitivity of prick and intradermal tests in the diagnosis of immediate reaction to betalactams mainly depends on the drug that elicited the reaction and the time elapsed from the clinical reaction. For penicillins the use of the major determinant (BPO-polylisine), a mixture of minor determinants (MDM), benzylpenicillin and aminopenicillins have a sensitivity of 60–90%. Taking into consideration that 10% of cases of penicillin allergy were made during rechallenge study, it supports the need to include this procedure in the study of penicillin allergy. This is particularly important in patients with immediate reactions sensitised only to aminopenicillin with good tolerance to penicillin and if the time elapsed from last reaction is more than 6 months. For immediate reactions to cephalosporins the sensitivity of the skin test is less than for penicillins, approximately 50%. For other betalactams the experience is limited and no conclusion can be drawn. The value of late reading of intradermal tests and the patch test in late reactions to betalactams is also limited but can be useful in approximately 40–80% of cases.