CODFISH ALLERGY IN ADULTS - SPECIFIC TESTS FOR IGE AND HISTAMINE-RELEASE VS DOUBLE-BLIND, PLACEBO-CONTROLLED CHALLENGES

Background At present, several in vitro tests for immunoglobulin E (Ig E)-mediated food allergy are available. An estimation of the diagnosti c accuracy of the various tests used in predicting clinical sensitivit y to codfish in a well-characterized allergic material is necessary. O bjectives To compare the diagnostic value of four specific IgE tests, and histamine release from basophils (HR) in identifying clinical type I allergy to codfish. As a true diagnosis, double-blind, placebo-cont rolled food challenges (DBPCFC) were employed. Methods Eight clinicall y codfish-allergic adult patients were investigated together with 30 c odfish-tolerant control subjects for evidence of codfish-specific reac tivity by Phadebas RAST(R) (PHA), Pharmacia CAP System RAST(R) (CAP), Magic(R) Lite (ML) and HR. To characterize the diagnostic properties o f a freshly prepared raw codfish extract, experiments were conducted e mploying an in-house radioallergosorbent test (RAST), the Maxisorp PAS T (MAXI) and HR. Finally, protein profile and IgE-reacting allergens w ere detected by means of sodium dodecyl sulfate-polyacrylamide gel ele ctrophoresis (SDS-PAGE) and immunoblotting. Results The sensitivities of HR with commercial extract and the three commercially available spe cific IgE analyses were 0.83 and 1.00 respectively. Specificities were 1.00 (HR) and 0.87-1.00 (specific IgE tests). Freshly prepared codfis h extracts improved the sensitivity of HR. SDS-PAGE revealed approxima te to 29 bands ( < 14.3-200 kDa) including a band of 12-13 kDa, and in immunoblotting 18 sera identified 17 IgE-binding bands. The protein m igrating at 12-13 kDa was identified in the fresh codfish extract test ed with sera from all clinical codfish allergies, while no significant reaction was seen in the control subjects. Conclusion Based on the sm all number of adult patients included in our study, the in vitro assay s with commercial and fresh extracts have high sensitivity and are acc eptable for screening for codfish allergy. Specificity of Phadebas, CA P, and our in-he use RAST was less than unity, whereas ML and strong b inding of IgE to a 12-13 kDa protein completely matches DBPCFC results , and thus seems sufficient for establishing the diagnosis.