Non-alcoholic steatohepatitis (NASH) is a stage of nonalcoholic fatty liver disease (NAFLD) characterized by the presence on liver biopsy of steatosis and of necroinflammation with variable amounts of fibrosis in individuals who no not consume alcohol to excess.

NASH may progress to cirrhosis in 15-25% of patients, and NASH-related cirrhosis is now considered the major cause of cryptogenic cirrhosis. Once cirrhosis develops, 30%-40% of these patients succumb to a liver-related death over a 10-year period.

The prevalence of NASH in morbidly obese persons ranges from 20%-35%, whereas simple steatosis (a benign condition) is present in approximately 70%. Obese patients are at particularly high risk for NASH in view of the frequent co-existence of other features of the metabolic syndrome. Liver biopsy is diagnostic but technically challenging in such individuals. This study was undertaken to develop a clinically useful scoring system to predict the probability of NASH in morbidly obese persons, thus assisting in the decision to perform liver biopsy.

Two hundred consecutive subjects undergoing bariatric surgery without evidence of other liver disease underwent intraoperative liver biopsy. Median body mass index was 48 kg/m² and the median age was 43 years. The outcome was pathologic diagnosis of NASH. Biopsies were interpreted by a single experienced liver histopathologist, who was blinded to the patients' clinical data.

A total of 186 patients, including 58 (31.2%) with NASH, were used for the multivariate analysis and creation of the Scoring System. Fourteen patients were omitted from the analysis because one or more of the independent predictive variables was not available. Multivariate analysis identified six independent predictive factors for the presence of NASH in the morbidly obese: hypertension, diabetes, AST≥27 IU/L, ALT≥27 IU/L, obstructive sleep apnea, and non-black race. These variables were then used to develop a NASH Clinical Scoring System for Morbid Obesity, which predicts the probability of NASH in four categories (low, intermediate, high, and very high).

The NASH Clinical Scoring System for Morbid Obesity derived in our study is based on data from patients who underwent bariatric surgery, which means it is limited to patients who have a BMI greater than 40 or those with a BMI greater than 35 together with obesity-associated diseases. However, the increasing incidence of morbid obesity in the United States, with an estimated prevalence of 14 million individuals, calls for the development of diagnostic and treatment strategies specific for this growing population.

The proposed clinical scoring can predict NASH in morbidly obese persons with sufficient accuracy to be considered for clinical use, identifying a very high-risk group in whom liver biopsy would be very likely to detect NASH, as well as a low-risk group in whom biopsy can be safely delayed or avoided.