The validation of histological criteria from the IAIH‐PG to distinguish AIH from drug‐induced liver injury

Background and aims To validate the applicability of the new histological criteria for autoimmune hepatitis (AIH) proposed by the International AIH Pathology Group (IAIH‐PG) among Chinese patients with AIH and drug‐induced liver injury (DILI). Methods The gold standard for diagnosis relied on clinical response: discontinuing treatment without relapse supported DILI, while relapse or ongoing immunosuppressive treatment confirmed AIH. This two‐centre retrospective cohort study included inpatients with DILI or AIH from January 2002 to March 2023. Cases that underwent liver biopsy were selected according to inclusion and exclusion criteria. The diagnostic performance of the criteria was assessed by an area under the receiver operating characteristic curve (AUROC). Results Out of 69 patients: AIH (41, 59%) and DILI (28, 41%). The accuracy, sensitivity and specificity of the new histological criteria for likely and possible AIH were 70%, 98% and 29%, respectively, with an AUROC of 0.8236 [95% confidence interval (CI): 0.7533–0.8938]. For likely AIH, the accuracy, sensitivity and specificity were 73%, 61% and 89%, respectively, with an AUROC of 0.9177 [95% CI: 0.8757–0.9596]. Moreover, for possible AIH, significant differences were found in serum alanine aminotransferase levels [178.4 (87.0, 435.0) versus 536.5 (206.9, 930.4) U/L] and antinuclear antibody (ANA) ≥1:160 [10 (67%) versus 1 (6%)], as well as in lobular lymphoplasmacytic infiltrate [15 (100%) versus 12 (71%)] and more than mild inflammation [13 (87%)versus 6 (35%)] between AIH and DILI (all P values were <0.05). Conclusion The new histological criteria exhibit good diagnostic efficacy in distinguishing AIH from DILI in China, with high AUROC. Key discriminators include low aminotransferase, ANA ≥1:160, lobular lymphoplasmacytic infiltrate and more than mild inflammation, which may further improve diagnostic accuracy for AIH.