Non-alcoholic steatohepatitis (NASH) is a liver condition characterized by fat accumulation, inflammation, and liver cell damage. It can progress to more severe forms of liver disease, including cirrhosis and liver cancer. To assess and track this condition, medical professionals use the NASH score. Understanding this tool is helpful for individuals concerned about liver health.
Understanding the NASH Score
The NASH score, formally known as the NAFLD Activity Score (NAS), serves as a standardized histological scoring system. Its purpose is to quantify disease activity in a liver biopsy, measuring inflammation and damage. The score helps distinguish NASH from simpler fatty liver disease and monitors changes over time.
Elements and Derivation of the Score
The NASH score is derived from an examination of a liver tissue sample. Pathologists evaluate three features: steatosis, lobular inflammation, and hepatocyte ballooning. Steatosis, fat accumulation in liver cells, is graded by percentage of affected cells. It is scored from 0 (less than 5% affected) to 3 (more than 66% affected).
Lobular inflammation indicates inflammatory cells within the liver’s lobules. It is scored from 0 (no foci of inflammation) to 3 (more than four foci per 200x field). Hepatocyte ballooning is the swelling and degeneration of liver cells. It is graded from 0 (none) to 2 (prominent ballooning).
These individual grades are summed to produce the overall NASH activity score, ranging from 0 to 8. Fibrosis, scarring of liver tissue, is a separate measure indicating disease progression, staged independently. Fibrosis staging ranges from F0 (no fibrosis) to F4 (cirrhosis), with higher stages indicating advanced scarring.
Interpreting Score Values
The numerical values of the NASH score provide important insights into the severity of liver disease activity. A higher NASH score generally indicates more pronounced inflammation and liver cell damage. Scores ranging from 0 to 2 typically suggest that NASH is unlikely or not diagnostic. A score between 3 and 4 may indicate borderline or indeterminate NASH, where the features are present but not definitively diagnostic.
A NASH score of 5 or higher strongly correlates with a diagnosis of definite NASH, signifying significant disease activity. While the NASH score reflects current disease activity, it is not used as a standalone diagnostic tool for NASH. It serves as an indicator of the extent of liver injury.
The fibrosis stage, assessed separately, is a determinant of overall prognosis and management, even if the NASH activity score is low. Fibrosis stages range from F0 (no fibrosis) to F4 (cirrhosis), with F2-F4 considered clinically significant. Advanced fibrosis (F3-F4) signifies more severe scarring and a higher risk of complications. This separate assessment highlights that even with mild inflammation, significant scarring can be present, influencing treatment and long-term outlook.
Contextualizing the Score in Patient Care
The NASH score is a valuable tool within the broader framework of managing non-alcoholic fatty liver disease (NAFLD) and NASH. It provides specific information about the microscopic changes occurring in the liver. However, this score represents only one piece of information for clinicians.
Patient care involves considering a comprehensive range of factors, including symptoms, other laboratory tests, and imaging studies. Blood tests, such as those that assess liver enzymes, and imaging techniques, like ultrasound or MRI, offer additional data points. The overall health status of an individual, including co-existing conditions, also influences clinical decisions. The NASH score helps guide treatment decisions and monitor disease progression, but it is integrated into a holistic approach to patient care that considers all available clinical information.