Spiking experiments using a known number of NCI-H1975 (10, 100, 1000 cells) spiked in 10 mL peripheral blood (PB) of healthy donors (HD) have shown that following Parsotrix enrichment, these cells were detected through CK-19 mRNA expression in all cases (Supplementary Fig. S1). This evidence concerns the gene KRT19 and Huntington disease.