Normalization was independent from the rEV quantification method used since implementation of a p24 ELISA to quantify rEV provided equivalent results in breast cancer patients compared to healthy individuals (1.59 × 1011 vs 7.55 × 1010) (p = 0.0009, Mann–Whitney test) (Fig. 5f) (supplementary table 2). Here, CD9 is linked to breast cancer.