Comparison of the basophil activation test versus the nasal provocation test in establishing eligibility for specific immunotherapy

INTRODUCTION    Allergic rhinitis (AR) is the most common atopic disease. Specific immunotherapy (SIT) is the only effective treatment method for AR. In uncertain diagnostic cases, before establishing eligibility for SIT, nasal provocation tests (NPTs) should be performed. However, there are numerous contraindications to performing NPTs, and there is ongoing search for an alternative in vitro method.
OBJECTIVES    The aim of the study was to determine whether a specific in vitro provocation, that is, the basophil activation test (BAT), may replace a specific in vivo provocation, that is, the NPT, in establishing patient’s eligibility for SIT.
PATIENTS AND METHODS    The study included 30 patients with AR caused by allergy to house dust mite or birch pollen, referred for SIT. The assessment of basophil activation by measuring CD63 antigen expression was performed using the Flow2 CAST test. Basophils were stimulated with allergen preparation (concentrations of 5000, 500, and 50 standardized biological units) used in NPTs. BAT results were expressed as stimulation index (SI) and basophil reactivity (BR).
RESULTS    Allergen concentrations of 500 and 50 SBU proved to be appropriate for basophil stimulation. Median SI and BR were higher for positive NPT results than for negative NPT results (P <0.001). Sensitivity for SI and BR was in the range from 83% to 100%; specificity, from 78% to 89%; positive predictive value, from 75% to 87%; and negative predictive value, from 89% to 100%. We observed a high correlation of the analyzed parameters for the allergen concentrations of 500 and 50 SBU (range, 0.58–0.74; P <0.05).
CONCLUSIONS    If there are contraindications to performing the NPT, BAT may be regarded as an alternative in establishing patients’ eligibility for SIT. The optimal concentrations of allergen preparations are 500 and 50 SBU. Both SI and BR are good indicators of basophil activation.