RESUMO
BACKGROUND: Vancomycin infusion reaction (VIR), reportedly mediated through Mas-Related G Protein-Coupled Receptor-X2 (MRGPRX2), is the primary vancomycin-induced immediate drug reaction (IDR). Clinically, distinguishing the underlying drug-induced IDR mechanisms is crucial for future treatment strategies, including drug restriction, re-administration, and pretreatment considerations. However, the lack of validated diagnostic tests makes this challenging, often leading to unnecessary drug restriction. OBJECTIVE: To determine if intradermal tests (IDTs) and, separately, the basophil activation test (BAT) differentiate VIR from vancomycin-tolerant subjects. METHODS: Cross-sectional study of vancomycin-exposed adults with and without a history of VIR. Demographics, allergy-related comorbidities, history of vancomycin exposures, and VIR characteristics were collected. IDT with vancomycin was performed. IDT dose responses EC50, IDT-related local symptoms, and BAT were compared between groups. RESULTS: 11 VIR and 10 vancomycin-tolerant subjects were enrolled. The most reported VIR symptoms were pruritus (82%), flushing (82%), hives (46%), hives (46%), angioedema (27%), and dyspnea (19%). The IDT dose response mean EC50 was 328 µg/mL (95% CI 296, 367) in the VIR vs. 1,166 µg/mL (95% CI 1029, 1379) in the tolerant group (p<0.0001). All VIR subjects reported IDT-related local pruritus compared to 60% of tolerant subjects (p=0.0185). The %CD63+ basophils were consistently <2%, without significant differences between groups (p < 0.54). CONCLUSIONS: Variations in skin test methodologies could help identify other IDR mechanisms beyond IgE. This skin test protocol holds the potential for identifying VIR, particularly in cases where patients have received multiple drugs while BAT is insufficient. Future studies will validate and delineate its predictive value, assessing the risk of VIR.