The use of basophil activation test in clinical practice
The BAT can have different applications in the day-to-day clinical setting - Table 2 summarises some of the possible indications of BAT, which can be categorized into three main groups: 1) confirmation of an allergy, 2) eligibility for a specific therapy and 3) monitoring of the natural resolution of an allergy or response to therapy. The confirmation of allergy is important for several reasons. Firstly, it improves the safety profile of diagnostic work-up, as it may defer the need for an oral food challenge, preventing potential anaphylactic reactions. Secondly, it allows confirming the indication for immune modifying therapies that may require prolonged exposure to medications before a clinical response is seen. Examples for this is the use of omalizumab in allergic asthma and initiation of oral food immunotherapy, both of which require many months on therapy to assess response. Thirdly, BAT may be useful to measure the response to treatment and act as a surrogate of in vivo allergen exposure, like in a food challenge. Even in cases where basophils show no response to allergen and the positive control, IgE (known as non-releaser or anergic basophils), data is emerging that is suggestive of this finding is more likely to indicate low clinical reactivity to allergen (24). Furthermore, BAT also has value in rare allergic disorders, such as allergic bronchopulmonary aspergillosis, as an additional criterion for diagnosis, particularly in patients who do not fulfill the minimal diagnostic criteria.
The use of the BAT to clinical practice requires analytical validation of the methodology, clinical validation of the test against patients’ phenotype and continued quality assurance57,87-89.