METAVIRproject

The METAVIR project refers to an international collaboration of hepatopathologists and researchers that produced a standardized histopathological scoring system for liver fibrosis and inflammatory activity, most prominently in chronic hepatitis C infection. Initiated in the late 1990s, the METAVIR scoring system was developed to enable consistent reporting of liver biopsy findings across clinical trials and routine practice, thereby improving comparability of results between laboratories and studies.

The METAVIR score comprises two independent axes: fibrosis and activity. The fibrosis scale is F0 to F4, where F0 indicates no fibrosis, F1 denotes portal/periportal fibrosis, F2 indicates few septa, F3 corresponds to numerous septa, and F4 signifies cirrhosis. The activity scale ranges from A0 to A3, with A0 representing no histologic activity, A1 mild inflammation, A2 moderate inflammation, and A3 severe activity. The separation into these two dimensions allows clinicians and researchers to assess structural damage (fibrosis) separately from inflammatory activity, supporting staging of disease and monitoring response to therapy.

The METAVIR system has been widely adopted in hepatitis C management and in many clinical trials as a standard method for histologic assessment. It has also been applied to other chronic liver diseases, though its original development targeted hepatitis C. The scoring system has contributed to improved consistency in biopsy interpretation and has been validated in numerous studies. Limitations include sampling variability inherent to liver biopsy and interobserver or intraobserver differences in scoring, as well as the inherent invasiveness of biopsy and the existence of non-invasive alternatives.