Superiority of Solenopsis invicta venom to whole-body extract in RAST for diagnosis of imported fire ant allergy.

RAST determinations using imported fire ant (IFA) whole-body extract (IFAWBE) and venom (IFAV) were performed with the sera of 29 sting-sensitive patients. Only 48% (14/29) of sera were positive (percent binding greater than or equal to 6%) in RAST to IFAWBE compared with 79% (23/29) positive to IFAV, and there was significantly greater binding to IFAV than to IFAWBE (p less than or equal to 0.0002). Thus, RAST with IFAV identified 31% more sting-sensitive individuals than RAST with IFAWBE, a finding similar to that noted in studies using IFAV and IFAWBE for skin testing. We conclude that IFAV is the more appropriate allergen for use in in vitro tests to detect IFA-specific IgE antibody in allergic patients.