[The usefulness and limitations of the radioallergosorbent test in diagnosing food allergy in atopic dermatitis].

To clarify the diagnostic value of the radioallergosorbent test (RAST), the relationship between RAST and the oral food challenge test was evaluated. 263 children with atopic dermatitis were challenged by egg, cow's milk or soy bean after their skin manifestations had been improved by elimination diet and environmental control. Of 200 cases with negative RAST results for egg white, 108 cases (54.0%) showed no reaction in egg challenge tests. However, 65 cases (31.5%) had non-immediate reactions, while 29 cases (14.5%) had immediate reactions (within 2 hours of challenge). Of 16 cases with RAST score of 1 for egg white, 11 cases (68.8%) had non-immediate reactions and 2 cases (12.5%) had immediate reactions in egg challenge tests. Of 19 cases with RAST scores of 2 for egg white, 2 cases (10.5%) had no reaction, 6 cases (31.6%) had non-immediate reactions and 11 cases (57.9%) had immediate reactions in egg challenge tests. Of 21 cases with RAST scores of 3 for egg white, 1 case (4.8%) had no reaction, 3 cases (14.3%) had non-immediate reactions and 17 cases (81.0%) had immediate reactions in egg challenge tests. All 7 cases with RAST scores of 4 for egg white had immediate reactions in egg challenge tests. Almost the same relationship between RAST and challenge tests were found in test using cow's milk or soy bean. In conclusion, false negative results were seen in 46.0% of RAST for egg white, 51.7% of RAST for cow's milk and 26.9% of RAST for soy bean.(ABSTRACT TRUNCATED AT 250 WORDS)