Clinical validation of the basophil activation test in immediate hypersensitivity reactions to gadolinium-based contrast agents

Gadolinium based contrast agents (GBCAs) are safe compounds globally used in magnetic resonance imaging (MRI). However, in last years it has been detected an increase of immediate hypersensitivity reactions (IHRs) to them. Diagnosis of IHRs to GBCAs is based on clinical symptoms, skin tests (STs) and drug provocation test (DPT). But DPTs are not without risks, thus it is important to implement an in vitro alternative method such as the basophil activation test (BAT). We described the clinical validation of the BAT using ROC curves from a control population formed by 40 healthy individuals without previous reactions to any contrast agents and 5 patients suffering from IHRs to GBCAs. Four patients presented IHRs to gadoteric acid (GA) as the culprit agent and another one to gadobutrol (G). Basophil reactivity was measured in percentage of CD63 expression and in stimulation index (SI). The optimal cut-off with the highest sensitivity (S) and specificity (E) for the GA was of 4.6% at 1:100 dilution (S = 80% and E = 85%; AUC = 0.880, p = 0.006). For the SI with GA, the cut-off of highest sensitivity and specificity was of 2.79 at 1:100 dilution (S = 80% and E = 100%; AUC = 0.920, p = 0.002). Sensitivity did not show differences between STs regarding the BAT (p < 0.05). Moreover, the BAT was able to detect one case with IHR to GA which had negative STs. Therefore, the BAT is a useful method in diagnosis of IHRs to GBCAs.