The ability of AdnaTest to discriminate between healthy subjects and patients was modest (AUC around 0.60) when using EPCAM and ERBB2 as surface antigens for CTC enrichment and classical epithelial- or tumour-associated markers (EPCAM, MUC1, and ERBB2) for detection, thus providing an explanation for different CTC detection rates and scarce concordance when comparing the two methods. The gene discussed is MUC1; the disease is neoplasm.