Fig. 2

Sensitivity and specificity of detection of rare cells using PACS. a Scatter-plot diagram of cell stain intensity values, and PTPRC (FAM, lymphocyte staining, left) or VIM (HEX, PC3 staining, right) fluorescence from multiplexed TaqMan assays. 44 out of 47 PC3 cells expressed VIM, and only 2 of 44 also expressed PTPRC. The blue lines represent the thresholds applied to differentiate clusters; the heat map correlates with drop counts. b Dynamic range of PACS. Different numbers of PC3 (blue circles) or DU145 (red circles) cancer cells were spiked in and sorted from a background of lymphocyte Raji cells. The scatter plot shows strong correlation between the number of cells spiked in and the number of VIM+ drops, with a recovery of 82 % and 75 % for PC3 and DU145, respectively. Straight lines represent the fit across spike-ins. c The scatter plot shows the reproducibility of the PACS workflow across spike-ins in the two cancer cell lines. The detection efficiency (number of spiked-in cells that show a positive TaqMan signal) is consistently above 89 % (blue line) and 85 % (red line) for PC3 and DU145 cells, respectively