Basophil Activation Tests Based on CD193 Marker in Dipyrone Allergy

414 http://e-aair.org I recently read the article Threshold for Positivity and Optimal Dipyrone Concentration in Flow Cytometry-Assisted Basophil Activation Test by Hagau et al., in the August 2013 issue of AAIR, where the authors assessed the usefulness of basophil activation tests (BATs) in the diagnosis of allergy to dipyrone. Allergy to dipyrone still represents a main concern and pyrazolones are considered a major cause of immediate IgE-mediated reactions to drugs in many countries. A case of drug rash with eosinophilia and systemic symptomatology (DRESS) attributed to dipyrone was recently reported; however, the authors could not rule out a possible interfering role attributed to herbal mixtures and other drugs. BATs represent an interesting tool to diagnose drug hypersensitivity, though with some criticism about their performance and interpretation. Basophils captured in flow cytometry by CD193 (CCR3)phycoerythrin (PE) may be contaminated by CD3 expressing cells, leading to possible bias. Despite this issue, Hagau and colleagues reported that commercial BAT equipped with a Flow2-CAST technique, showed a sensitivity as low as 0.25 μg/mL dipyrone, about 3 orders of magnitude lower than previous reported evidence. In the paper by Gomez et al., a commercial BAT using an anti-IgE/CD63 protocol (instead of a CCR3/CD63) reported that the lowest dose able to trigger CD63 upregulation over the 5% threshold, was 0.25 mg/mL dipyrone (matamizole); Hagau and co-workers used the same CD63% threshold. It apppears quite difficult to attribute this sensitivity improvement to superior BAT performance (at least in regards to the phenotyping protocol). CCR3 has been recently reviewed as a phenotyping marker and compared to other flow cytometry approaches. The eotaxin receptor is commonly expressed on eosinophils, together with CD63 (which is only present on activated cells); however, in a SSC (side scatter)/CCR3 scatter plot, eosinophils and basophils can be clearly separated and eosinophils should not affect a Flow2-CAST BAT performance. Yet CCR3 is downregulated Basophil Activation Tests Based on CD193 Marker in Dipyrone Allergy