The use of two multitests fx5 and fx10 in the diagnosis of food allergy in children: regarding 42 cases.

The multitests Cap RAST fx5 and fx10 (Pharmacia, Cap System) are used for a rapid biological diagnosis of food allergy. These tests were assessed in 29 children who presented 42 food allergies (FA) documented by prick tests, specific IgE and labial or oral provocation tests (single blind placebo controlled food challenges). When the multitests were positive, the search for specific IgE to the corresponding allergens was performed (Cap RAST, Pharmacia). The theoretical coverage of FA could be estimated according to the frequency of food allergens involved in the children. It reaches 85% for Cap RAST fx5 and 29% for Cap RAST fx10. The sensitivity of Cap RAST fx5 is 89% and 50% for Cap RAST fx10. Even in the case when the child had a single food allergy, the detail of specific IgE showed multiple positivities to several allergens included in the multitest. Consequently, the positive predictive value of Cap RAST was only 32%. Prick tests to the same allergens were more rarely positive, gaining thus a better positive predictive value. The authors propose the use of Cap RAST fx5, eventually completed by a Cap RAST to beef for the first approach of food allergy in children. They stress the point that prick tests have to be carried on subsequently, in order to select properly allergens responsible for food allergy.