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Eberlein-Konig et al. (1) reported re-evaluation of their recently published data (2) on basophil activation with CD63 in 57 patients with hymenoptera allergy, in which they re-calculated the basophil 0.1/1 sensitivity ratio (3) and controlled for side-effects during the first week of immunotherapy. The 0.1/1 sensitivity ratio in 14 patients with side-effects was 81.4% and in 43 patients without side-effects was 75.4%. They found no significant difference between those two groups.

Our recent approach (3) was directed to evaluate basophil sensitivity to allergen-specific in vitro stimulation. Therefore, we calculated the ratio of basophil CD63 expression between a value on the plateau of the dose–response curve and a value on the steep part of the curve. The ratio between those two selected allergen concentrations (in our method 0.1 and 1 μg/ml, i.e. 0.1/1 sensitivity ratio) was representing the shift of the increasing dose-dependent basophil activation curve (median response at 0.1 was 50% of the response at 1). Of course, even more accurate approaches to measuring basophil sensitivity to the allergen exist, like concentrations giving 50% of maximum CD63 upregulation, as described in the article by Nopp et al. (4).

Obviously, in the article of Eberlein-Konig et al. the allergen concentration of 0.1 μg/ml was close to the plateau of the dose–response curve. Eberlein–Konig used the ‘BASOTEST’ method (Orpegen Pharma) and ALK allergens. For ‘BASOTEST’, Erdmann et al. (5) showed even slightly higher mean basophil CD63 response at 0.1 then at 1 μg/ml of venom concentration in 50 wasp allergic patients. For that reason, re-calculations of Eberlein–Konig probably better represent basophil maximal response (ratio at the top of dose–response) than basophil sensitivity. Another reason which precludes direct comparison of results at certain allergen concentrations was the method used for gating basophils. Eberlein–Konig used anti-IgE and we used CD123 and HLA-DR as markers of basophils.

MacGlashan (6) showed that basophil sensitivity is an independent intrinsic property which does not correlate with maximal response. Therefore, sensitivity measured by a basophil activation test should be specifically evaluated for each clinical and/or research application.

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