Fig. 2.

Receiver operating characteristic (ROC) curve analysis for diagnostic performance of IGRA. The ROC analyzes the ability of IGRA to discriminate INFγ response in vaccinated HCWs (T2) versus baseline INFγ response (T0) to the Spike antigen of SARS-CoV-2.The Youden index (i.e., cutoff at the highest sum of specificity and sensitivity) is 72 mIU/mL. The area under the ROC curve (AUC) is 1.000 (95 CI, 0.981–1.000)