Serum samples from eighty-one patients with suspected penicillin allergy were investigated with Phadebas RAST using the penicillin derivatives Benzylpenicilloyl-human serum albumin (PBO-HSA) and Phenoxymethylpenicilloyl-human serum albumin (PMPO-HSA) and the results were compared with skin test results and clinical data.
Of the sixty-one patients who had anaphylactic shock and/or urticaria as a possible consequence of penicillin administration, reagins against PBO-HSA and PMPO-HSA could be detected in thirty-four cases (56%). Five per cent of these patients, with positive RAST results, showed negative skin tests; in the other 95% both RAST and skin tests were positive. All, except eight, of the RAST-negative patients had had their adverse reactions at least 2 years prior to the blood sampling and in some of these cases skin tests were also negative. RAST and provocation test results agreed in 80% of the cases where exposition was performed. It is concluded that the RAST technique is a valuable diagnostic tool for the detection of immediate type hypersensitivity to penicillin.