Evaluation of EUS-guided FNA for Diagnosing Autoimmune Pancreatitis: a Prospective, Single-center Study

Patients who suggested having Autoimmune pancreatitis (AIP) and underwent endoscopic ultrasound-guided fine needle aspiration (EUS-FNA） by using a standard 22-gauge aspiration needle were enrolled between January 2013 and May 2017. The enrollment criteria included age greater than 20 years at the time of enrollment; presence of imaging characteristics of AIP, as specified in the International Consensus Diagnostic Criteria（ICDC） (diffuse or segmental/focal enlargement with delayed enhancement and diffuse or segmental/focal or multiple irregular narrowing of the main pancreatic duct without marked upstream dilatation) was confirmed by computed tomography (CT), magnetic resonance imaging (MRI), or EUS. The exclusion criteria were steroid administration within 3 months before the initiation of treatment; refusal or inability to provide informed consent; episode of acute pancreatitis in previous 2 weeks; inability to safely perform EUS-FNA, such as cardiorespiratory dysfunction, mental diseases, coagulopathy and drug addiction.All procedures were performed under deep sedation by a single experienced endosonographer who had performed more than 500 cases. EUS-FNA was performed by using Olympus linear echoendoscopes , Diagnostic Ultrasound System and 22-G needle . Once the lesion was evaluated by EUS, the echoendoscopist would select the shortest pathway, while avoiding blood vessels, to reach the lesion. Under real-time visualization, slow-pull technique and suction technique were used to punctured each lesions. The specimens were expelled onto glass slides, and then prepared for histological and cytological examinations. Because neither pathologists nor cytologists were present on-site at our institution, the puncture was repeated until a whitish material could be observed macroscopically.Tissue samples were fixed in formalin and embedded in paraffin. A paraffin block was thin cut into serial sections and stained with hematoxylin-eosin(H&E). To detect infiltrated plasma cells, anti-IgG4 antibody would be done if necessary. The histologic analysis was made by an experienced pathologist who was blind to the kinds of studies referring to the histological criteria of the ICDC. The Lymphoplasmacytic sclerosing pancreatitis (LPSP ) findings are as follow: (1) Periductal lymphoplasmacytic infiltrate without granulocytic infiltration; (2) Obliterative phlebitis; (3)Storiform fibrosis; (4) Abundant (>10cells/HPF) immunoglobulin G4 (IgG 4)positive cells. The level-1 criteria of LPSP were positive for 3 or more of the 4 LPSP findings, and the level-2 criteria were positive for 2 of the 4 items. The idiopathic duct-centric chronic pancreatitis (IDCP) findings are as follow: (1) Granulocytic infiltration of duct wall (GEL) with or without granulocytic acinar inflammation; (2)Granulocytic and lymphoplasmacytic acinar infiltrate; (3)Absent or scant (0-10 cells/ High-power fields) IgG4-positive cells. The level-1 criteria of IDCP were positive for items (1) and (3), and the level-2 criteria were positive for items (2) and (3).Statistical analyses were performed with Statistical Analysis System (SAS) version 9.2. All tests were 2-tailed and a P value of less than 0.05 was considered to indicate a statistically significant difference. All category variables will be described in terms of the count and percentage using the χ 2 test, whereas the continuous variables will be described as mean ± standard deviation using τ tests or Wilcoxon rank-sum tests. Outpatients were observed for immediate complications in the recovery room for 2 hours and followed up on the day after the procedure to monitor for possible complications.