Controlled Attenuation Parameter in Nonalcoholic Fatty Liver Disease: The Thresholds Do Matter

Diagnosis and assessment of disease severity in patients with nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) includes simple steatosis, nonalcoholic steatohepatitis (NASH), fibrosis, and eventually cirrhosis and hepatocellular carcinoma (HCC). The diagnosis of NAFLD is based on the detection of excess fat disposition in the liver, which is the first step to trigger further evaluation of NAFLD, including necroinflammation and fibrosis. In this review, we discuss non-invasive biomarkers and imaging tools that are currently and potentially available for different features (steatosis, necroinflammation and fibrosis) and disease severity assessment of NAFLD. In the past 2 decades, advances in non-invasive tests of fibrosis have transformed the management of NAFLD. Blood and imaging biomarkers have already been evaluated in multiple studies for the diagnosis of fibrosis and cirrhosis. Among the various histological features of NAFLD, the degree of fibrosis has the strongest correlation with liver-related morbidity and mortality. Non-invasive tests of fibrosis have been shown to predict liver-related outcomes, both in the general population and among patients with NAFLD. What is lacking, however, is good data to support the use of non-invasive tests as monitoring and response biomarkers. With the conclusion of several large phase 3 studies in the next few years, the availability of paired liver biopsy, non-invasive test and clinical outcome data will likely advance the field and shed light on new biomarkers and the way to use various non-invasive tests in a longitudinal manner.

Relationship between controlled attenuated parameter and magnetic resonance imaging-proton density fat fraction for evaluating hepatic steatosis in patients with NAFLD

We used cross-sectional and longitudinal studies to comprehensively compare hepatic steatosis measurements obtained with magnetic resonance imaging-proton density fat fraction (MRI-PDFF) and controlled attenuated parameter (CAP) in hepatic steatosis in adults with nonalcoholic fatty liver disease (NAFLD). A total of 185 participants with NAFLD and 12 non-NAFLD controls were recruited. CAP and MRI-PDFF data were collected at baseline from all participants and from 95 patients included in the longitudinal study after 24 weeks of drug or placebo intervention. Pearson correlation, linear regression, and piecewise linear regression analyses were used to evaluate the relationship between the two modalities. Linear analysis suggested a positive correlation between CAP and MRI-PDFF (r = 0.577, p < 0.0001); however, piecewise linear regression showed no correlation when CAP was ≥331 dB/m (p = 0.535). In the longitudinal study, both the absolute and relative change measurements were correlated between the two modalities; however, the correlation was stronger for the relative change (relative r = 0.598, absolute r = 0.492; p < 0.0001). Piecewise linear regression analysis revealed no correlation when CAP was reduced by more than 53 dB/m (p = 0.193). Conclusions: We found a correlation between CAP and MRI-PDFF measurements for grading hepatic steatosis when CAP was <331 dB/m. While the measured absolute change and relative change were correlated, it was stronger for the relative change. These findings have implications for the clinical utility of CAP or MRI-PDFF in the clinical diagnosis and assessment of NAFLD.

Fatty Liver Index for Predicting Nonalcoholic Fatty Liver Disease in an Asymptomatic Korean Population

Nonalcoholic fatty liver disease (NAFLD) is increasing worldwide, highlighting the importance of early and accurate detection and the appropriate management of NAFLD. However, ultrasonography (US) is not included in many mass screening programs, and people have limited access to it. The aim of this study is to validate the fatty liver index (FLI) and investigate the optimal cutoff value for predicting NAFLD in an asymptomatic population. We conducted a retrospective cohort study in Korea. All subjects who underwent health checkup exams, including abdominal US, controlled attenuation parameter (CAP) and blood testing, were enrolled. Analyses of the area under the receiver operating characteristic curve (AUROC) were used to evaluate the diagnostic accuracy and to calculate the optimal FLI cutoff for US-NAFLD. Among the 4009 subjects (mean age 54.9 years, 83.5% male), the prevalence of US-diagnosed NAFLD and CAP-defined hepatic steatosis was 61.4% and 55.4%. The previously used cutoff of FLI = 60 showed poor performance in predicting US-diagnosed NAFLD, with an AUROC of 0.63 (0.62–0.64), and CAP-defined NAFLD, with an AUROC 0.63 (0.62–0.64). The optimal FLI cutoff values to discriminate fatty liver detected by US were 29 for the entire population, with an AUROC of 0.82 (0.81–0.84). The sex-specific values were 31 for males and 18 for females (sensitivity 72.8% and 73.4%; specificity 74.2% and 85.0%, respectively). The FLI cutoff for US-diagnosed NAFLD can be set as 29 for the entire Korean population. Considering the sex dimorphism in NAFLD, different cutoff values are suggested to predict US-diagnosed NAFLD. These results may be helpful in the accurate non-invasive diagnosis of NAFLD.

Diagnostic Accuracy of Non-Imaging and Ultrasound-Based Assessment of Hepatic Steatosis Using Controlled Attenuation Parameter (CAP) as Reference

Background & Aims: In view of the limited reliability of biopsies in the assessment of liver fat, a non-invasive, trustworthy, and more accessible method estimating a degree of steatosis is urgently needed. While the controlled attenuation parameter (CAP) is used to quantify hepatic fat, its availability in routine practice is limited. Therefore, the aim of this study was to compare the diagnostic accuracy of biomarker- and ultrasound-based techniques for the diagnosis and grading of hepatic steatosis. Methods: This was a prospective study of 167 adults with and without non-alcoholic fatty liver disease. As measured against CAP, we assessed Hamaguchi’s score and the hepatorenal index (HRI), and the following biochemical measures: the fatty liver index, hepatic steatosis index, and lipid accumulation product scores during a single out-patient visit. Area under the receiver operating curve (AUROC) analyses were used to evaluate the diagnostic accuracy of each test and to calculate optimal thresholds for the ultrasound techniques. Results: All non-invasive methods displayed high accuracy in detecting steatosis (mean AUC value ≥ 0.90), with Hamaguchi’s score and the HRI being the most precise. These two tests also had the highest sensitivity and specificity (82.2% and 100%; 86.9% and 94.8%, respectively). We propose new thresholds for Hamaguchi’s score and HRI for hepatic steatosis grading, indicated by optimal sensitivity and specificity. Conclusions: Ultrasound-based techniques are the most accurate for assessing liver steatosis compared to other non-invasive tests. Given the accessibility of ultrasonography, this finding is of practical importance for the assessment of liver steatosis in clinical settings.