Type 1 autoimmune pancreatitis: clinical features and independent predictors of histopathological confirmation via EUS-guided fine-needle aspiration/fine-needle biopsy.

BACKGROUND: In diagnosing type 1 autoimmune pancreatitis (AIP), serum IgG4 (sIgG4) can be false-negative. EUS-guided fine-needle aspiration/biopsy (EUS-FNA/FNB) pathology is key for diagnosis, but clinical features’ impact on pathologic confirmation is unclear. This study analyzed their link and factors improve diagnostic accuracy. METHODS: We analyzed data from a single-center retrospective study at Changhai Hospital (Jan 2009-Jan 2024). Type 1 AIP was diagnosed per International Consensus Diagnostic Criteria (ICDC). Patients with surgical diagnosis, no EUS, or incomplete biopsy data were excluded; eligible cases were grouped into “Confirmed”/“Unconfirmed” per ICDC. Baseline data, laboratory indicators, imaging, and EUS-FNA/FNB data were collected. Statistical analyses (ROC, χ² tests, multivariate logistic regression) were done with R 4.4.0. RESULTS: A total of 182 suspected type 1 AIP patients were enrolled; 84.07% were male, 88.46% middle-aged/elderly. Common symptoms: abdominal discomfort (65.93%), obstructive jaundice (43.41%). sIgG4 > 2×ULN (twice upper normal limit) occurred in 64.84%. Multivariate analysis: pathological confirmation rate 65.12% (EUS-FNB) vs. 18.75% (EUS-FNA) (P < .001, former higher). For IgG4-positive cells: 82.56% confirmation rate (> 10 cells/high-power field[HPF]) vs. 16.67% (< 10 cells/HPF) (P < .001). EUS-FNB (OR = 3.56, 95% CI: 1.55–8.18, P = .003) and IgG4-positive cell count (> 10 cells/HPF) (OR = 15.71, 95% CI: 6.96–35.46, P < .001) were independent confirmation predictors. Gender, age, sIgG4 had limited value; renal involvement, retroperitoneal fibrosis were auxiliary indicators. CONCLUSIONS: Following systematic multi-dimensional factor screening, pathological confirmation of type 1 AIP relies on two key factors: EUS-FNB and histopathological detection of IgG4-positive cells (> 10 cells/HPF). Integrating these core diagnostic modalities with additional indicators—such as auxiliary markers of extrapancreatic involvement (e.g., renal involvement)—further enhances diagnostic precision, which facilitates the refinement of clinical diagnostic workflows for type 1 AIP.