Ambispective Validation of the Odesa Criteria 2026 (OC26): A Flexible Point-Based System for Diagnosis of Autoimmune Pancreatitis.

Approval Number protocol 020237 Board Name Ethics Committee of the Military Medical Clinical Center of the Southern Region. Board Affiliation Military Medical Clinical Center of the Southern Region, Ukraine. Board Contact Information Phone: +380 (50) 316-10-54)

Autoimmune pancreatitis (AIP) remains one of the most diagnostically challenging pancreatic disorders due to its heterogeneous presentation, overlap with pancreatic cancer, and variability in imaging, serology, and histology. Existing diagnostic frameworks-including the HISORt criteria, ICDC, and Asian guidelines-provide valuable structure but often lack flexibility in real-world clinical settings, especially when complete diagnostic data are unavailable. The Odesa Criteria 2026 (OC26) were developed as a practical, point-based diagnostic system designed to integrate clinical, serological, radiological, and morphological features of AIP into a unified, flexible scoring model. Unlike rigid categorical criteria, OC26 allows proportional weighting of diagnostic domains and supports decision-making even when certain data elements are missing. This approach reflects real clinical practice and aims to reduce diagnostic uncertainty, unnecessary surgical interventions, and delays in steroid therapy. This ambispective study includes a retrospective cohort of patients evaluated for suspected AIP over the past five years and a prospective cohort enrolled during the ongoing study period. All available clinical records, laboratory data, imaging studies, endoscopic findings, and histopathology reports are systematically reviewed and scored according to the OC26 framework. The primary objective is to validate the diagnostic accuracy of OC26 compared with established international criteria. Secondary objectives include assessment of interobserver agreement, evaluation of OC26 performance in incomplete datasets, and analysis of its ability to differentiate AIP from pancreatic malignancy. The study is non-interventional and observational. No experimental treatments are administered. All diagnostic and therapeutic decisions are made according to standard clinical practice. Data collection includes only routinely obtained clinical information. The study is expected to provide a robust evidence base for the clinical utility of the Odesa Criteria 2026 and support their integration into international diagnostic algorithms for autoimmune pancreatitis.

Inclusion Criteria: * Adults (≥18 years) undergoing evaluation for suspected autoimmune pancreatitis. * Availability of clinical, serological, imaging, and/or histological data required for OC26 scoring. * Ability to provide informed consent (for prospective participants). Exclusion Criteria: * Confirmed alternative diagnosis explaining pancreatic findings (e.g., pancreatic cancer, acute pancreatitis of other etiology). * Incomplete diagnostic data preventing OC26 scoring. * Prior pancreatic surgery altering diagnostic interpretation.