Serum apoptotic caspase activity as a marker of severity in HBeAg-negative chronic hepatitis B virus infection

Background and aim: In chronic hepatitis C and nonalcoholic fatty liver disease, apoptotic caspases are activated in liver, and serum caspase activity has been suggested as a sensitive marker of early liver injury. An investigation was carried out into whether the serum levels of caspase-generated fragments of cytokeratin-18 (CK-18) are associated with the severity of liver lesions in hepatitis B e antigen (HBeAg)-negative chronic hepatitis B virus (HBV) infection. Patients/methods: CK-18 fragment serum levels were determined in 115 treatment-naive, consecutive HBV patients and 30 healthy controls. Hepatic-expression of CK-18 fragments was evaluated by immunocytochemistry in chronic hepatitis B patients. Results: CK-18 fragment levels (U/l) were significantly lower in healthy controls (mean (SD), 154 (31)) than in 53 inactive carriers (172 (24), p=0.003) and in 62 chronic hepatitis B patients (474 (488), p<0.001). The receiver operating characteristic curve showed excellent diagnostic accuracy (c-statistic: 0.87) for differentiating inactive carriers from chronic hepatitis B patients. A CK-18 fragment cut-off level of 240 U/l gave a sensitivity of 60%, and a specificity and positive predictive value of 100% for chronic hepatitis B diagnosis. CK-18 fragment levels were also lower in inactive carriers than in 16 chronic hepatitis B patients with transiently normal alanine aminotransferase (ALT; 327 (256), p=0.001), offering good accuracy for such a differentiation (c-statistic: 0.78). In chronic hepatitis B patients, serum CK-18 fragments correlated positively with ALT/aspartate aminotransferase (AST), viraemia, grading score and their immunohistochemical hepatic expression, and negatively with platelet counts, but not with fibrosis or steatosis severity. Conclusions: Serum apoptotic caspase activity is strongly associated with the presence of liver injury in patients with HBeAg-negative chronic HBV infection. CK-18 fragment levels seem to be a very useful marker for differentiation between the inactive HBV carrier state and HBeAg-negative chronic hepatitis B, but not for estimation of the severity of liver histological lesions among HBeAg-negative chronic hepatitis B patients.