Extracellular Vesicle-Derived miRNAs as Diagnostic Biomarkers for Pancreatic Ductal Adenocarcinoma: A Systematic Review of Methodological Rigour and Clinical Applicability.

Background: Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignancy with currently limited early detection options. Extracellular vesicle (EV)-derived microRNAs (miRNAs) have gained interest as non-invasive diagnostic biomarkers due to their stability in circulation and tumour-specific profiles. However, the methodological robustness of existing literature remains unclear. Objectives: To systematically evaluate the diagnostic accuracy and methodological quality of studies investigating EV-derived miRNAs for PDAC detection, with a particular focus on adherence to established EV characterisation guidelines. Design: Systematic review registered with PROSPERO (CRD42024501503) and conducted in accordance with PRISMA 2020 reporting standards. Methods: We searched PubMed, EMBASE, Medline and Cochrane for original human studies published up to February 1, 2025, evaluating EV-derived miRNAs in biofluids from PDAC patients. Eligible studies reported diagnostic accuracy metrics (sensitivity, specificity, Area Under the Curve (AUC)). Methodological quality was assessed using the QUADAS-2 tool, and EV validation was scored against the Minimal Information for Studies of Extracellular Vesicles 2018 (MISEV) 2018 checklist (updated 2023). Results: Fifty-six studies were included. Plasma and serum were the most commonly used biofluids. The most frequently evaluated individual miRNAs were miR-21 (13 studies), miR-10b (9 studies), and miR-451a (7 studies). Although several studies reported high diagnostic performance (AUCs up to 0.99), MISEV adherence was limited: only 23.1% of miR-21 studies demonstrated strong EV validation, and >70% of all studies lacked EV quantification or protein marker analysis. Multi-miRNA panels achieved higher AUCs (often > 0.85) but typically scored poorly on EV characterisation. Only 2 of 56 studies included external validation, and 54 studies lacked blinding, contributing to substantial risk of bias. Conclusion: EV-derived miRNAs are promising PDAC biomarkers, but progress is hindered by inconsistent methods, poor EV validation, and minimal external verification. Translation to clinical use requires robust EV characterisation, standardised workflows, and prospective multi-cohort studies.