Benefit of the basophil activation test in deciding when to reintroduce cow's milk in allergic children

Oral challenges are required to establish the persistence or resolution of IgE-mediated cow's milk allergy (CMA). Determining the appropriate timing for challenging is the main difficulty. The benefit of the basophil activation test (BAT) in predicting a child's reaction to the oral challenge was evaluated and compared to the specific IgE and skin prick tests' (SPT) results.

One hundred and twelve consecutive children with CMA admitted for an oral challenge to reassess their allergy were included. Allergen-induced basophil activation was detected as a CD63-upregulation by flow cytometry.

Thirty-six children (32%) had a positive oral challenge. The percentage of activated basophils in patients with a positive challenge (mean = 20.9; SD = 18.8) was significantly higher than that of patients with a negative challenge (mean = 3.9; SD = 9.8, P < 0.0001), and was well correlated with the eliciting dose of cow's milk (P < 0.0001). The BAT had an efficiency of 90%, a sensitivity of 91%, a specificity of 90%, and positive and negative predictive values of 81% and 96% in detecting persistently allergic patients. The area under the ROC curve was 0.866. These scores were higher than those obtained with SPT and IgE values, whichever positivity cut-point was chosen. Referring to a decisional algorithm combining BAT, specific IgE and SPT allowed the correct identification of 94% of patients as tolerant or persistently allergic to cow's milk proteins (CMP) in our cohort.

The BAT could be a valuable tool in the management of paediatric CMA in addition to specific IgE quantification and SPT, by contributing in determining whether an oral challenge can safely be undertaken.