Diagnosis of ciprofloxacin hypersensitivity improves by incorporating MRGPRX2 in basophil activation test

Background: Immediate hypersensitivity reactions (IHR) to ciprofloxacin can be caused by Mas-related G-protein coupled receptor X2 (MRGPRX2) as well as immunoglobulin E (IgE)-dependent mechanisms. When considering the complexity of the Patho mechanism, there are doubts with regard to the adequacy of conventional basophil activation test (BAT) in diagnosing fluoroquinolone-induced IHR. Our aim was to present a BAT method that relies on specifically evaluating the basophils expressing MRGPRX2 to increase the diagnosis rate of ciprofloxacin-induced MRGPRX2-mediated IHR. Methods: CD63 and MRGPRX2 expressions were analyzed with and without ciprofloxacin stimulation on basophils from patients and healthy controls by using flow cytometry. The net percentage of upregulation (net%) of MRGPRX2 and CD63 on basophils were statistically analyzed. Results: Fourteen patients with confirmed IHR to ciprofloxacin and age- and gender-matched 12 healthy controls were analyzed. The median (interquartile range) age of the patients was 39.5 years (33.5-51.5 years) and 92.9% were women. The median (interquartile range) net% expression of CD63 on basophils, MRGPRX2 on basophils, and CD63 on MRGPRX2⁺ basophils after ciprofloxacin stimulation was all higher in patients (18.1 [5.8-25.3], 3.7 [3.0-5.4], and 13.9 [7.8-28.8], respectively) compared with healthy controls (6.6 [3.8-11.4], 2.4 [0.6-3.7], and 1.3 [0.4-8.9], respectively) (p = 0.027, p = 0.042, and p = 0.001, respectively). Receiver operating characteristic analysis showed that the net% of CD63 expression on MRGPRX2⁺ basophils had a greater area under the curve to predict ciprofloxacin IHR than did the net% of CD63 expression on basophils. A net% > 10.3% of CD63 expression on basophils showed a sensitivity of 71.4% and a specificity of 75.0%, whereas a net% > 3.9% of theCD63 expression on MRGPRX2⁺ basophils showed a sensitivity of 100% and a specificity of 75.0%. The proposed method diagnosed four more patients compared with the conventional BAT. Conclusion: Analysis of our data indicated that the determination of MRGPRX2 together with CD63 in basophils improves the in vitro diagnosis of ciprofloxacin IHR with a better sensitivity compared with conventional BAT.