INTRADERMAL COMPARED WITH PRICK TESTING IN THE DIAGNOSIS OF ANESTHETIC ALLERGY

We have tested the hypothesis that intradermal testing is a more effec tive method for determining the drug responsible for anaesthetic anaph ylactic reactions than prick testing in 212 consecutive patients, aged more than 10 yr, referred to an anaesthetic allergy clinic over a 4-y r period. The study was a prospective, non-randomized design. Intrader mal testing was conducted using a previously described method and dilu ted drugs, and prick testing using undiluted drugs (with the exception of opioid analgesics which were diluted 1:10). The tests were perform ed on individual patients' forearms on the same occasion. Patients wer e followed-up to determine the results of subsequent anaesthesia and t he difference between tests was analysed using kappa and tau statistic s. There was 93% agreement overall between the paired tests. Which tes t detected the drug responsible was dependent on diagnostic criteria f or positivity. The differences between the tests were not statisticall y significant. Using both tests improved predictability by 67% (tau=0. 67, P<0.001). We conclude that in the absence of data to support one t est being superior, other factors influence the choice of test. Prick testing was cheaper, and the reduction in pain and trauma with prick t esting makes it more suitable for children. However, there are no data available on the safety of subsequent anaesthesia based on the result s of prick testing alone, and reliability with time has not been asses sed. Intradermal testing may be easier for the infrequent user. Skin t esting is valuable in the investigation of anaesthetic anaphylaxis whi chever test is chosen. When there is doubt both tests should be perfor med.