Diagnostic Value of Serum Adenosine Deaminase and Its Isoenzymes for Autoimmune Liver Disease

Background: Adenosine Deaminase (ADA) has been found to be involved in autoimmune disease progression. Objectives: We aimed to evaluate the diagnostic value of serum ADA activity in Autoimmune Liver Disease (AILD). Methods: The study included 50 AILD patients, 33 viral hepatitis patients, and 60 healthy subjects. The serum levels of total Adenosine Deaminase (tADA) and its isoenzymes (ADA1 and ADA2) were determined. The Receiver Operating Characteristic (ROC) curve analysis was used to evaluate the diagnostic performance of serum ADA activity. Results: Our results showed that the serum tADA and ADA2 levels were significantly higher in AILD patients (tADA: 19 (IQR 14 - 24) U/L; ADA2: 16 (IQR 10 - 19) U/L) than in healthy controls (tADA: 9 (IQR 7 - 11) U/L; ADA2: 7 (IQR 6 - 9) U/L), while there was no significant difference in serum ADA1 activity between AILD and healthy subjects. Based on the ROC curves analysis, the optimal cutoff values of serum tADA and ADA2 activity were 11.5 and 9.5 U/L, respectively. At this level, the highest diagnostic values of tADA (specificity: 83.3%; sensitivity: 88%) and ADA2 (specificity: 85.0%; sensitivity: 82%) were obtained. Moreover, our results showed no significant difference in serum tADA, ADA1, and ADA2 levels between AILD and viral hepatitis patients (P = 0.049; P = 0.29; P = 0.054). Conclusions: Serum ADA activity can be used to distinguish AILD patients from healthy subjects, but it cannot be used in the differential diagnosis of AILD and viral patients.