Sonographic assessment of fatty liver: intraobserver and interobserver variability

Non-alcoholic fatty liver disease (NAFLD) is a common liver disease worldwide and ultrasonography is widely used in the diagnosis and the follow-up we purposed to assess intraobserver and interobserver variability in the sonographic evaluation of the existence and steatosis grades of NAFLD. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels and AST to ALT (AST/ALT) ratio were compared between the grades of hepatosteatosis. Hepatic ultrasonography (US) examinations consisted of 5-10 static images of 113 successive adult patients, whose records were in the picture archiving and communication system (PACS) of our hospital were retrospectively evaluated by two experienced radiologists. Hepatic images were graded into 4 groups; as normal, mild, moderate or severe hepatic steatosis. Evaluation of hepatic steatosis of the same set of images was repeated after one month under the same conditions. Interobserver and intraobserver agreement was assessed by using kappa (κ) statistics. In each group, the percentage of individuals with high ALT and/or AST, or AST/ALT ratio over 1 was calculated. The intraobserver agreement was 51%, fair kappa (κ=0.356) for observer 1; and 68%, moderate (κ=0.591) for observer 2. The interobserver agreements in the initial and second readings were 39% and 40%, fair (κ=0.208) and (κ=0.225), respectively. Elevations of ALT and/or AST levels were similar between groups depending on the degree of hepatosteatosis among the patients. Visual assessment of NAFLD by ultrasonography has substantial interobserver variability, and reproducibility of results is limited. More objective imaging modalities are needed to evaluate the degree of hepatosteatosis.