Diagnostic value of the skin-prick test and RAST assay in insect sting allergy

The results of skin-prick tests to four concentrations of venom (0.1, 1, 10 and 1000 micrograms/ml) carried out on two occasions were analysed in relation to the history of adverse reactions to stings and to the level of venom-specific IgE antibody in serum, in forty-two subjects allergic to insect stings (sixteen to bee and twenty-six to wasp). Fifty control subjects (some of whom had never been stung by bee or wasp) with no history of adverse reaction to stings were also studied. No subject gave a positive skin-test reaction to 0.1 microgram/ml, and small numbers reacted to either 1 or 10 micrograms/ml. The lowest concentration of venom to which most subjects had a positive skin test was 100 micrograms/ml. Our data suggest that in wasp-allergic patients a positive skin test to 100 micrograms/ml is normally significant (reflecting the presence of specific IgE), whereas in bee-allergic patients a skin test reaction to 100 micrograms/ml is usually non-specific for the following reasons. (i) In the allergic patients when skin tests were repeated, a reaction to 100 micrograms/ml bee venom often became negative (in six of eight), whereas for wasp venom the reaction became more positive (at 10 or 1 micrograms/ml) in seven of eight patients. Whilst this might reflect lack of reproducibility, the consistent direction of change for either bee or wasp venom suggests responses to this concentration of these venoms may have different interpretations.(ABSTRACT TRUNCATED AT 250 WORDS)