Fatty liver indices in the multiethnic United States National Health and Nutrition Examination Survey

BACKGROUND: Validated non-invasive measures of fatty liver are needed that can be applied across populations and over time. A fatty liver index (FLI) including body mass index, waist circumference, triglycerides and gamma glutamyltransferase (GGT) activity was developed in an Italian municipality, but has not been validated widely or examined in a multiethnic population. AIMS: We evaluated this FLI in the multiethnic U.S. National Health and Nutrition Examination Survey (NHANES) and also to explore whether an improved index for the U.S. population (US FLI) could be derived. The US FLI would then used to examine U.S. time trends in fatty liver prevalence. METHODS: We studied 5869 fasted, viral hepatitis negative adult participants with abdominal ultrasound data on fatty liver in the 1988-1994 NHANES. Time trend analyses included 21 712 NHANES 1988-1994 and 1999-2012 participants. RESULTS: The prevalence of fatty liver was 20%. For the FLI, the area under the receiver operating characteristic curve [AUC; 95% confidence interval (CI)] was 0.78 (0.74-0.81). The US FLI included age, race-ethnicity, waist circumference, GGT activity, fasting insulin and fasting glucose and had an AUC (95% CI) of 0.80 (0.77-0.83). Defining fatty liver as a US FLI ≥ 30, the prevalence increased from 18% in 1988-1991 to 29% in 1999-2000 to 31% in 2011-2012. CONCLUSIONS: For predicting fatty liver, the US FLI was a modest improvement over the FLI in the multiethnic U.S. population. Using this measure, the fatty liver prevalence in the U.S. population increased substantially over two decades.