Finally, we compared the performance of the method developed in this study to that of conventional deep sequencing. Since the presence of KRAS mutations is used as the standard for identifying ctDNA in patients with pancreatic cancer, we compared the ability of our method to detect KRAS mutations to that of conventional deep sequencing. In the first analysis, we analyzed our sequence data without using the molecular barcodes, thus regarding them as conventional deep sequencing data. In the second analysis, we utilized the data from a large-scale case-control study of a population of European descent by Le Calvez-Kelm et al.  conducted using deep sequencing. Sensitivity and specificity were respectively defined as the proportion of KRAS mutation-positive samples among samples from patients of pancreatic cancer and the proportion of KRAS mutation-negative samples among samples from the control population. The control population in the first analysis included healthy individuals as well as IPMN patients. The respective calculated sensitivity and specificity were as follows: NOIR-SS/CV78 (our data), 25.9% and 100%; deep sequencing (our data), 30.8% and 96.9%; and deep sequencing (data from Le Calvez-Kelm et al.), 20.9% and 96.3%. Two-by-two tables and representative parameters are shown in S6 Table. In comparison, the sensitivity of two previous studies that used droplet digital PCR [20, 21] was 32.0%. These two studies did not report the specificity of their method using control populations.