Discrimination of mucinous pancreatic cysts using an enzymatic turnover assay to improve clinical diagnostic accuracy.

4151 Background: One impact of medical imaging technology has been an approximately 3-fold increase in the incidental detection of pancreatic cysts during routine clinical examinations. To reduce burden on the healthcare system and patients, clinicians desire accurate classification of pancreatic cysts into benign non-mucinous or potentially malignant, mucinous populations. Using EUS-FNA, fluid from these cysts can provide molecular biomarkers of predictive value. However, current in vitro diagnostics lack the desired sensitivity and specificity for clinicians to accurately stratify patients for risk of pre-malignant cancers. This situation can be improved by introducing new biomarkers and novel assay platforms. An enzymatic biomarker, pepsin C, has shown high accuracy for diagnosing mucinous cysts. The use of enzymatic activity assays is applicable to clinical workflows without disruption of current standards of care. Methods: A pepsin C activity assay using a magnetic bead-based platform was developed, with both fluorescent and surface-enhanced Raman spectroscopy (SERS) readouts. The assay platform utilizes selective peptide substrates, and a dimeric Rhodamine-6G-based dye, which allows ultrasensitive detection and significantly decreases the sample volume requirement for analysis, down to 1 µL of cyst fluid. The dye-labeled substrate is immobilized on magnetic beads and reacted with enzyme-containing samples to produce a quantitative assay signal that is standardized and expressed in true enzyme activity units. Results: While both readouts were quantitative and produced linear standard curves, SERS-based analysis was more robust against established biological matrix effects than fluorescence. Nevertheless, both assay modes successfully differentiated mucinous and non-mucinous cysts in a retrospective cohort of 69 cyst fluid samples. Compared with the standard of care CEA assay, this activity-based assay displays much improved sensitivity in diagnosing mucinous pancreatic cysts (Table). Conclusions: This pepsin c activity assay differentiates between mucinous and non-mucinous cysts better than the CEA assay and provides a quantifiable standardized readout. This work establishes a path to a true rule-out assay enabling clinicians to better stratify patients into low risk vs. potential malignancy thus impacting treatment and monitoring plans. [Table: see text]