In the previous study, Koomen et al. reported that a set of 4 peaks could be used to detect PDAC, of which one MS signal was downregulated in PDAC patients and found to be derived from apolipoprotein A-I [23], while Yan et al. found that transthyretin levels were independently associated with PDAC likelihood when obstructive jaundice was considered [36]. This evidence concerns the gene TTR and obstructive jaundice.