Monitoring of CD19 CAR T cells and CD19.CAR⁺EVs in patients treated with CD19 CAR T cells. A total of 22 patients were monitored for 2 years from CD19 CAR T-cell infusion. The concentration of circulating CD19 CAR T cells was monitored both by flow cytometry (purple line) and ddPCR (blue line). CD19 CAR T-cell monitoring was paralleled with the concentration of CD19.CAR⁺EVs (red line). Flow cytometry analysis of CD19.CAR⁺EVs in responding vs nonresponding patients is also shown. Data were log transformed. A 2-way analysis of variance (ANOVA), followed by Tukey multiple comparisons test, was performed. An alpha value of .05 was established for the significance threshold. Each time point represents the mean (+SEM) of at least 3 independent measurements from distinct patients. Data are represented as mean + SEM; Mann-Whitney nonparametric test, and Robust Regression followed by OUTlier Identification test for outliers were applied.