The aim of this study is to compare the diagnostic accuracy of two EUS-guided tissue acquisition devices; the 19G Echotip Ultra Fine Needle Aspiration (FNA) device and the 20G Echotip ProCore Fine Needle Biopsy (FNB) device for the diagnosis of autoimmune pancreatitis.

Endoscopic ultrasound (EUS)-guided tissue acquisition has emerged as a valuable method to diagnose autoimmune pancreatitis (AIP) and exclude malignancy. During Endoscopic Ultrasound (EUS), tissue samples can be obtained for pathological evaluation with different devices. Previous studies suggest 19-gauge fine needle aspiration (FNA) needle provides a reliable specimen for diagnosis of AIP. However tissue architecture and cell morphology are essential for accurate pathological assessment. Therefore, pathologists generally prefer a histological specimen. Fine needle biopsy (FNB) has the advantage of obtaining a histological specimen, which may lead to better diagnostic performance. However, the superiority of histology over cytology in EUS-guided tissue sampling for diagnosis of AIP has not been proven yet. In this study, we aim to compare the diagnostic accuracy of two EUS-guided tissue acquisition devices; the 19G Echotip Ultra Fine Needle Aspiration (FNA) device and the 20G Echotip ProCore Fine Needle Biopsy (FNB) device for the diagnosis of autoimmune pancreatitis.

Inclusion Criteria:

• Patients referred for EUS-guided tissue acquisition because of clinical suspicion of AIP
• Age > 18 years
• Written informed consent

Exclusion Criteria:

• Known bleeding disorder that cannot be sufficiently corrected with co-fact or fresh frozen plasma (FFP)
• Use of anticoagulants that cannot be discontinued in order to guarantee an INR below 1.5
• Previous inclusion in the current study
• Pregnancy