THE USE OF SKIN TESTING IN THE INVESTIGATION OF CUTANEOUS ADVERSE DRUG-REACTIONS

Skin testing with the suspected compound has been reported to be helpf ul in determining the cause of cutaneous adverse drug reactions (ADRs) , but the value and specificity of these tests need to be determined. In this study, 72 patients with presumed drug eruptions (27 maculopapu lar, 18 urticarial, seven erythrodermic, nine eczematous, four photose nsitivity, three fixed drug eruptions, three with pruritus and one wit h acute generalized exanthematous pustulosis) were assessed. All had d rug patch tests; 46 also had prick tests and 30 had intradermal tests (performed on hospitalized patients using a sterile solution of the su spected drug, diluted sequentially) with immediate and delayed reading s. Among these patients, 52 (72%) had a positive skin test reaction, 4 3%, 24% and 67% in patch, prick and intradermal skin tests, respective ly. The results of skin tests varied with the drug tested and with the clinical type of cutaneous ADR, as a significantly higher number of p ositive patch tests was observed in maculopapular rashes than in urtic arial reactions (P=0.001). This study supports the value of careful se quential drug skin testing in establishing the cause of cutaneous ADR. Guidelines are proposed for performing these tests, and these include the use of appropriate negative control patients to avoid false-posit ive results.