Intradermal (ID) and prick tests with bee or wasp venom (Pharmalgen) have been performed on 102 subjects with a history of adverse reactions to stings and forty-six control subjects giving no such history. Venom was diluted 100, 10 and 1 μg/ml for prick testing and 10-2, 10-2, 10-3 and 10-4%mUg/ml for ID injections.
In forty-six control subjects all were tested with the highest concentration of prick testing solution (100 μg/ml), eight (17%) had positive reactions, a similar reaction rate to that reported in control subjects using 10-1μg/ml ID. In our 102 test subjects skin tests were therefore regarded as positive only if the reaction was elicited by 10-2μg/ml or less by prick test of 10-2μg/ml or less ID.
In general the results with skin prick tests and ID tests were comparable when the prick solution was 1000 times the concentration of that used for ID testing. ID tests were positive in thirteen with negative skin prick, seven of whom had detectable antibodies when tested by RAST. Conversely four with a positive skin prick test (two of whom were RAST positive) were considered negative on ID testing. As judged either by RAST or skin tests it appeared that sensitivity diminished with the time interval from the last sting (P< 0-001).