Double-blind, placebo-controlled food challenges in Brazilian children: adaptation to clinical practice

A double-blind, placebo-controlled food challenge (DBPCFC) is considered the gold standard for diagnosing food allergy, but because of methodological difficulties it is rarely conducted in clinical practice, especially in paediatric patients. The purpose of the study was to propose a DBPCFC protocol that is adapted to our conditions for the diagnosis of an IgE-mediated cow's milk allergy (CMA) in a Brazilian reference centre for paediatric allergies.

This study includes the experimental phase (choice of materials, adjustments made to protocols described in the literature) and the test execution phase. DBPCFCs were performed in 58 patients aged 1-15 years who were separated into two groups: Group 1 (n=39), sex 1.6 M:F, 5.3 years median age, suggestive history of IgE-mediated CMA; and Group 2 (n=19), sex 1.4 M:F, 8.3 years median age with symptoms not associated with milk ingestion and laboratory data not compatible with IgE-mediated CMA.

The materials were standardised for testing: containers and disposable products, low-lactose cow's milk (CM) and vehicles, such as natural fruit juice, vegetable soup and soybean-based beverages. Each DBPCFC was performed in a single day with two blind, randomised phases with a 2-h interval between them. The milk doses were gradually increased and offered in regular intervals of 15-30 min. Following negative or inconclusive results, patients underwent an open oral challenge test with 200 mL of low-lactose CM.

The proposed adaptation for the DBPCFC allowed to implement this important test for the diagnosis of IgE-mediated CMA in a reference centre for paediatric allergies. It was considered feasible and safe if performed in an appropriate setting with physician supervision.