Could BAT reduce the number of oral food challenge? A prospective study

Food allergy is a public health problem. Oral food challenge (OFC), the gold standard test for the diagnosis of food allergy, is also used to determine the threshold dose for specific immunotherapy. Nevertheless, it is not devoid of serious reactions. Basophil activation test (BAT) is an alternative test without risk for the child which simulates in vitro what happens in vivo during OFC. The primary outcome of our study was to determine if the BAT is able to predict the threshold dose and the clinical reaction that might be occurred during OFC. The secondary outcome was to determine BAT expression markers threshold causing reactions in children during OFC in order to replace the OFC by the BAT. Our study was carried out at the department of Pediatric. Only children with a suspected peanut allergy and performing an OFC were included. BAT were performed just before the OFC on the same day, testing 5 standards dilution of allergen. We evaluated CDmax, CDsens and AUC for the peanut whole extract f13 and Ara h2 based on the CD63 and CD203 expression on basophils. We included 41 children. F13-Specific IgE range from 0.19 to > 100 KUI/mL and Ara h2-specific IgE range from 0.23 to > 100 KUI/mL and OFC were negative in 17 patients and positive in 24. AUC and CDmax were significantly higher in OFC positive patients compared to OFC negative patients for the two allergens tested based on CD63 and CD203 expression (p < 0.0001 for all). There was no significant difference on CDsens in the two groups. We next assessed the correlation existing between the threshold dose during OFC and AUC/CDmax. CD63 CDmax and AUC have significant result for the two allergens tested (r=0.75 and r=0.73 respectively for both f13 and Ara h 2, p<0.0001) compared to CD203 CDmax and AUC. Finally, we observed a significant correlation between clinical graduation during OFC with CDmax and AUC for both allergen but not for CDsens, demonstrating that AUC and CDmax seems to be the best markers. Measurement of CDmax (63 and 203) and AUC (63 and 203) up-regulation on basophils also represents a valuable help in diagnosing allergy without OFC. These markers could predict the positivity of OFC as well as the severity of the allergic reaction and the threshold dose.