Introduction Although recommended in published guidelines, only 62% of UK Gastroenterologists routinely recommend diagnostic liver biopsy in patients with suspected AIH (Dhaliwal Gut 2012:62). Also, the relative usefulness of the International AIH Group diagnostic criteria (full 1999 or simplified 2008) is not established. Our aim was to assess the relationships between histological and immunological diagnostic features and response to treatment in patients meeting the 1999 IAIHG criteria, which we also assessed against the 2008 simplified criteria.

Method 90 patients were identified; 79% women, with median age 61 yrs (14–85) presenting since 2006 with suspected AIH and underwent diagnostic liver biopsy. Histology was assessed using the Ishak system by one liver Histopathologist (AKD) without reference to other results.

Results Interface hepatitis was found in 87(97%) of biopsies, mainly plasma cell infiltrate in 74(83%), rosettes in 68(76%) and emperipolesis in 100% (of 48 patients assessed). Biliary changes were seen in 14% and mild steatosis in 24%. Prior to biopsy, patients had 13(7–19) diagnostic points by IAIHG criteria, with 11 of the 90 patients not having the required 10 points. Biopsy contributed an additional 5(0–6) points and all patients then met the 1999 IAIHG criteria (61 definite, 29 probable) with 17(12–22) points. In 49 patients, with a pre biopsy score of >13, biopsy contributed 4(0–5) points and was not needed for diagnosis of AIH but detected biliary changes in 10 patients (3 AMA -ve,1 weak +ve subsequently diagnosed as PBC and started on treatment, 2 PSC overlap and 4 not overlap) and also detected cirrhosis in 9. Histological features did not differ between: patients with (n = 68) and without (n = 22) serum autoantibodies (nuclear, smooth muscle or LKM-1); between those with (n = 72) and without (n = 10) raised serum IgG; or between treated patients who did (n = 75) and did not (n = 8) achieve normal serum ALT within 6 months. Eighteen patients (20%) did not meet the 2008 simplified diagnostic criteria for AIH (6 points). In these, necro-inflammatory score was 9(2–15), fibrosis score was 3(0–5) and 13 of 14 treated patients achieved normal serum ALT by 6 months.

Conclusion Liver biopsy is important for diagnosis of AIH in those with lower, but less so in those with higher pre-biopsy IAIHG (1999) diagnostic scores. It may also detect cirrhosis or indicate additional unsuspected biliary disease. Histological features are not associated with immunological features or response to treatment. The 2008 simplified diagnostic criteria will “miss” 20% of patients with AIH by 1999 criteria. Most of these patients have significant disease and respond to treatment.

Disclosure of interest None Declared.