Abstract: Objective To investigate the relationship between serum adenosine deaminase (ADA) level and hepatic inflammatory activity in patients with autoimmune hepatitis (AIH). Methods Forty-six patients with AIH treated in our department from June 2015 to January 2019 were included. The inclusion criteria of AIH were based on the consensus on the diagnosis and treatment of autoimmune hepatitis developed by the Chinese Society of Hepatology, Chinese Medical Association in 2015. The measurement data of normal distribution were presented as mean ± standard deviation, and compared by t-test. The measurement data of non-normal distribution were presented as median (percentage 25, percentage 75), and compared by Kruskal-Wallis H test. The count data were presented as absolute value, and compared by chi-square test. And the correlation between the level of serum ADA and the grade of inflammation in liver tissue was analyzed by Spearman correlation coefficient. The diagnostic efficacy of serum ADA level in liver inflammation was evaluated by receiver operator characteristic curve (ROC curve). Results There were 46 patients with AIH, including 17 males and 29 females, with an average age of (43.3 ± 11.8) years. There were 2 cases of Grade (G) 0, 5 cases of G1, 11 cases of G2, 16 cases of G3 and 12 cases of G4. There were significant differences in ADA levels among AIH patients in G0 [11.8 (10.2, 15.2) U/L], G1 [13.4 (10.8, 16.7) U/L], G2 [17.4 (12.8, 20.4) U/L], G3 [22.7 (17.6, 28.7) U/L] and G4 [23.8 (18.1, 29.6) U/L] (P<0.05). Spearman correlation analysis showed that the level of serum ADA was positively correlated with the grade of inflammation in liver tissue (r=0.72, P<0.05). The cut-off value in diagnosis of mild inflammation in liver tissue and the areas under ROC curve (AUC) were 13.2 U/L and 0.72. The cut-off value and AUC in diagnosis of moderate inflammation were 16.8 U/L and 0.76. And the cut-off value and AUC in diagnosis of severe inflammation were 23.4 U/L and 0.88. Conclusion The level of serum ADA is positively correlated with the inflammatory activity of liver tissue in patients with AIH, which has ideal diagnostic value for severe inflammation of liver tissue, and can be used as a potential serological index to predict the inflammatory activity of liver tissue in patients with AIH.

Key words: Autoimmune hepatitis, Adenosine deaminase, Hepatic inflammation, Receiver operating characteristic curve