Quantitative Hepatic Fat Quantification in Non-alcoholic Fatty Liver Disease Using Ultrasound-Based Techniques: A Review of Literature and Their Diagnostic Performance

Non-alcoholic fatty liver disease is a condition that is characterized by the presence of >5% fat in the liver and affects more than one billion people worldwide. If adequate and early precautions are not taken, non-alcoholic fatty liver disease can progress to cirrhosis and death. The current reference standard for detecting hepatic steatosis is a liver biopsy. However, because of the potential morbidity associated with liver biopsies, non-invasive imaging biomarkers have been extensively investigated. Magnetic resonance imaging-based methods have proven accuracy in quantifying liver steatosis; however, these techniques are costly and have limited availability. Ultrasound-based quantitative imaging techniques are increasingly utilized because of their widespread availability, ease of use and relative cost-effectiveness. Several ultrasound-based liver fat quantification techniques have been investigated, including techniques that measure changes in the acoustic properties of the liver caused by the presence of fat. In this review, we focus on quantitative ultrasound approaches and their diagnostic performance in the realm of non-alcoholic fatty liver disease.

Reproducibility and accuracy of a pocket-size ultrasound device in assessing liver steatosis

BACKGROUND

This diagnostic prospective study compared the feasibility and diagnostic accuracy of Pocket-size Ultrasound Devices (PUDs) against standard ultrasound (US) in detecting liver steatosis using the controlled attenuation parameter (CAP) and liver biopsy as reference standards.

MATERIALS AND METHODS

Consecutive patients with chronic liver diseases were assessed for the presence of steatosis using PUD and US. A CAP cut-off value >275 dB/m was applied to establish ≥S1. A 26-patient subgroup underwent liver biopsy. PUD reproducibility was evaluated using Cohen's k statistic. Diagnostic accuracy of PUD and US was given as Sensibility (Sn), Specificity (Sp), Positive and Negative Predictive Values (PPV, NPV), positive and negative Likelihood Ratio (LR+, LR-).

RESULTS

81 consecutive patients (69% males) with multiple etiologies were enroled. PUD inter-observer agreement was good (k 0.77, 95%CI 0.62-0.93). PUD and US identified ≥S1 according to CAP values respectively with Sn 0.87, Sp 0.61, PPV 0.49, NPV 0.91, LR+ 2.04, LR- 0.07, AUROC 0.74 and Sn 0.96, Sp 0.54, PPV 0.47, NPV 0.97, LR+ 2.10, LR- 0.07, AUROC 0.75.

CONCLUSIONS

PUD shows good reproducibility and diagnostic accuracy in ruling liver steatosis out, representing a useful point-of-care tool to avail of hepatologists interested in excluding NAFLD, but with basic US skills.