Impact of EUS-guided fine-needle biopsy sampling on International Consensus Diagnostic Criteria for diagnosing autoimmune pancreatitis: a prospective multicenter study

Background and Aims: Histologic diagnosis of autoimmune pancreatitis (AIP) may be difficult to obtain preoperatively. Based on promising results using new-generation "end-cutting" needles, we aimed to assess the utility of EUS-guided fine-needle biopsy (EUS-FNB) sampling in enhancing diagnostic levels of International Consensus Diagnostic Criteria (ICDC) in patients with probable AIP and in defining the specific AIP subtype. Methods: Adult patients with suspected AIP were prospectively and competitively enrolled at 4 centers. Definitive AIP diagnosis, according to the ICDC, or patients recently treated with steroids were excluded. A 22-gauge end-cutting needle was used in all cases. The primary outcome was the rate of enhanced ICDC levels. Secondary outcomes were rates of levels 1 or 2, EUS-FNB diagnostic accuracy, rate of malignancy, and safety. Results: Fifty-two patients with focal (50) and diffuse (2) suspected AIP were enrolled (75% men; mean age, 57.9 +/- 17.3 years). Final diagnoses were AIP, chronic pancreatitis, and malignancy in 39 (75%), 6 (11.5%), and 7 (13.5%) patients, respectively. EUS-FNB improved the diagnostic level of AIP in 92.3% (74.3% definitive and 17.9% probable). The rate of histology level 1 compatible with a diagnosis of type 1 and type 2 AIP was 73.1% and 50%, respectively. The rate of histology level 2 was 23.1% and 41.7% in type 1 and type 2, respectively. The overall diagnostic accuracy of EUS-FNB was 94.2% (95% CI, 84.1-98.8). Two mild cases of pancreatitis (3.8%) occurred after EUS-FNB. Conclusions: EUS-FNB using end-cutting needles enhanced the ICDC in >90% of patients, ruling out malignancy in focal presentations and defining the specific subtype of AIP. (Clinical trial registration number: NCT04397731.) (Gastrointest Endosc 2025;102:559-68.)