Interobserver study of liver histopathology using the Ishak score in patients with chronic hepatitis C virus infection

Background: Assessing the histopathological degree of liver damage is essential to the routine care of patients with chronic hepatitis C virus (HCV) infection. Several scoring systems have been proposed in attempts to standardize the histological assessment. One scoring system has been proposed by Ishak et al, Although widely endorsed, its interobserver reliability has not been evaluated. Methods: 95 liver biopsies from patients with chronic HCV infection were scored by three independent observers. Interface hepatitis, confluent necrosis, focal necrosis, portal inflammation, and fibrosis were assessed. Results. Confluent necrosis, which is more common in acute hepatitis, was not seen in any biopsy. For each of the remaining variables of inflammation (periportal hepatitis, focal necrosis, and portal inflammation) we found agreement in 95-96% for all three observers. Kappa scores ranged from 0.11 to 0.41 and weighted kappa scores from 0.18 to 0.53. For staging we noted 84% agreement, kappa scores of 0.26-0.47 and weighted kappa scores of 0.57-0.69. Conclusion. The Ishak system is associated with good interobserver reliability if a deviance of one categorical level in each variable of the system is accepted as agreement. Compared to the Knodell system it provides more detailed information but is less reliable regarding fibrosis.