Background: The majority of histopathological classifications of primary chronic viral hepatitis and recurrence of HCV infection in liver transplants is based on the histological activity index (HAI) introduced by Knodell et al in 1981; however, correlation between HAI and clinical/laboratory data is poor. Therefore, the aim of this study was to present a modification of HAI (mHAI) adapted to distinct features of graft infection, and to evaluate its usefulness in the description of disease activity.
Material/Methods: Inflammatory activity in 67 biopsies of HCV-infected grafted livers was semi-quantitatively assessed according to HAI based on Knodell’s criteria and to mHAI proposed by the authors. Patients were divided into 4 groups according to level of clinical aggressiveness of HCV reinfection on the basis of laboratory data. Correlations between clinical aggressiveness and histological activity of the disease expressed as HAI or mHAI was estimated.
Results: Histological features of HCV reinfection of various activity were observed as early as in the second month after orthotopic liver transplantation. HAI and mHAI values were similar in 55.2% of cases, but in 38.8% HAI was lower than mHAI. Morphological and clinical features were found to be consistent in 32.8% and 49.3% of cases for HAI and mHAI evaluation, respectively. mHAI seems to correlate with clinical assessment of HCV recurrence in liver grafts significantly better than does the classical HAI.
Conclusions: mHAI proposed in the present study appears to be more useful for evaluation of recurrence of HCV infection in post-transplant liver biopsies.

Keywords: Liver Transplantation, HCV reinfection, HAI (histological activity index)