Ultrasound-guided percutaneous core-needle biopsy for the diagnosis of type 1 autoimmune pancreatitis

This study aimed to investigate the usefulness of ultrasound-guided core-needle biopsy (US-CNB) for diagnosing type 1 AIP and evaluate the radiological outcomes following steroid therapy.

From January 2017 to June 2023, patients with pathology results containing "lymphoplasmacytic infiltration" and "fibrosis" were enrolled. The detection rate of level 1 histology by International Consensus Diagnostic Criteria (ICDC) and the contribution of US-CNB were assessed. The radiological responses to steroid therapy following biopsy were assessed and classified.

Sixty-one patients were included, 56 of whom ended up with a diagnosis of type 1 AIP. Twenty-six (46.4%, 26/56) patients met the level 1 criteria of type 1 AIP. Of the 61 enrolled patients, 27 (44.3%) were diagnosed with definitive type 1 AIP without evidence from histology. The addition of pathologic evaluation of the pancreas tissue collected by US-CNB improved the diagnostic rate of definitive type 1 AIP to 67.2% (44.3% vs. 67.2%, p = 0.017). Among the remaining 20 undiagnosed patients, 13 (21.3%) finally were diagnosed with definitive type 1 AIP, and 2 (3.3%) with probable type 1 AIP by a diagnostic steroid trial (67.2% vs. 91.8%, p = 0.001). At the 12-month follow-up, a favorable response was observed in 48 patients, a partial response in 5 patients, relapse in 1 patient and disease progression in 2 patients.

US-CNB is an effective diagnostic method for type 1 AIP. A high remission rate of AIP was achieved with the addition of US-CNB to the diagnostic algorithm.