Diagnostic Accuracy of Shear Wave Elastography as a Non-invasive Biomarker of High-Risk Non-alcoholic Steatohepatitis in Patients with Non-alcoholic Fatty Liver Disease

How to Identify Advanced Fibrosis in Adult Patients with Non-Alcoholic Fatty Liver Disease (NAFLD) and Non-Alcoholic Steatohepatitis (NASH) Using Ultrasound Elastography-A Review of the Literature and Proposed Multistep Approach

Non-alcoholic fatty liver disease (NAFLD), and its progressive form, non-alcoholic steatohepatitis (NASH), represent, nowadays, real challenges for the healthcare system. Liver fibrosis is the most important prognostic factor for NAFLD, and advanced fibrosis is associated with higher liver-related mortality rates. Therefore, the key issues in NAFLD are the differentiation of NASH from simple steatosis and identification of advanced hepatic fibrosis. We critically reviewed the ultrasound (US) elastography techniques for the quantitative characterization of fibrosis, steatosis, and inflammation in NAFLD and NASH, with a specific focus on how to differentiate advanced fibrosis in adult patients. Vibration-controlled transient elastography (VCTE) is still the most utilized and validated elastography method for liver fibrosis assessment. The recently developed point shear wave elastography (pSWE) and two-dimensional shear wave elastography (2D-SWE) techniques that use multiparametric approaches could bring essential improvements to diagnosis and risk stratification.

Accuracy of Noninvasive Diagnostic Tests for the Detection of Significant and Advanced Fibrosis Stages in Nonalcoholic Fatty Liver Disease: A Systematic Literature Review of the US Studies

BACKGROUND

The purpose of this systematic literature review (SLR) was to evaluate the accuracy of noninvasive diagnostic tools in detecting significant or advanced (F2/F3) fibrosis among patients with nonalcoholic fatty liver (NAFL) in the US healthcare context.

METHODS

The SLR was conducted in PubMed and Web of Science, with an additional hand search of public domains and citations, in line with the PRISMA statement. The study included US-based original research on diagnostic test sensitivity, specificity and accuracy.

RESULTS

Twenty studies were included in qualitative evidence synthesis. Imaging techniques with the highest diagnostic accuracy in F2/F3 detection and differentiation were magnetic resonance elastography and vibration-controlled transient elastography. The most promising standard blood biomarkers were NAFLD fibrosis score and FIB-4. The novel diagnostic tools showed good overall accuracy, particularly a score composed of body mass index, GGT, 25-OH-vitamin D, and platelet count. The novel approaches in liver fibrosis detection successfully combine imaging techniques and blood biomarkers.

CONCLUSIONS

While noninvasive techniques could overcome some limitations of liver biopsy, a tool that would provide a sufficiently sensitive and reliable estimate of changes in fibrosis development and regression is still missing.

Hepatic Fat Quantification With Novel Ultrasound Based Techniques: A Diagnostic Performance Study Using Magnetic Resonance Imaging Proton Density Fat Fraction as Reference Standard

Purpose: To assess the diagnostic performances of novel Tissue attenuation imaging (TAI) and Tissue scatter distribution imaging (TSI) tools in quantification of liver fat content using magnetic resonance imaging proton density fat fraction (MRI PDFF) as reference standard. Methods: Eighty consecutive patients with known or suspected non-alcoholic fatty liver disease (NAFLD) who volunteered to participate in the study comprised the study cohort. All patients underwent MRI PDFF scan and quantitative ultrasound (QUS) imaging using TAI and TSI tools. The cutoff values of ≥5%, ≥16.3% and ≥21.7% on MRI PDFF were used for mild, moderate and severe steatosis, respectively. Area under the Receiver operating characteristic (AUROC) curves were used to assess the diagnostic performance of TAI and TSI in detecting different grades of hepatic steatosis. Results: The AUROCs of TAI and TSI tools in detecting hepatosteatosis (MRI PDFF ≥5%), were 0.95 [95% Confidence Interval (CI): 0.91–0.99] ( P < 0.001) and 0.96 (95% CI: 0.93–0.99) ( P < 0.001), respectively. In distinguishing between different grades of steatosis, the values of 0.75, 0.86 and 0.96 dB/cm/MHz have 88%, 88% and 100% sensitivity, respectively, for TAI tool; and the values of 92.44, 96.64 and 99.45 have 90%, 92% and 91.7% sensitivity, respectively, for TSI tool. Conclusion: TAI and TSI tools accurately quantify liver fat content and can be used for the assessment and grading of hepatosteatosis in patients with known or suspected NAFLD.

Liver fibrosis assessment: MR and US elastography

Elastography has emerged as a preferred non-invasive imaging technique for the clinical assessment of liver fibrosis. Elastography methods provide liver stiffness measurement (LSM) as a surrogate quantitative biomarker for fibrosis burden in chronic liver disease (CLD). Elastography can be performed either with ultrasound or MRI. Currently available ultrasound-based methods include strain elastography, two-dimensional shear wave elastography (2D-SWE), point shear wave elastography (pSWE), and vibration-controlled transient elastography (VCTE). MR Elastography (MRE) is widely available as two-dimensional gradient echo MRE (2D-GRE-MRE) technique. US-based methods provide estimated Young's modulus (eYM) and MRE provides magnitude of the complex shear modulus. MRE and ultrasound methods have proven to be accurate methods for detection of advanced liver fibrosis and cirrhosis. Other clinical applications of elastography include liver decompensation prediction, and differentiation of non-alcoholic steatohepatitis (NASH) from simple steatosis (SS). In this review, we briefly describe the different elastography methods, discuss current clinical applications, and provide an overview of advances in the field of liver elastography.

Diagnosis of steatohepatitis and fibrosis in biopsy-proven nonalcoholic fatty liver diseases: including two-dimension real-time shear wave elastography and noninvasive fibrotic biomarker scores

BACKGROUND

The aim of this retrospective study was to evaluate the accuracy of two-dimension real-time shear wave elastography (2D-SWE) for the diagnosis of steatohepatitis and fibrosis in a cohort patients confirmed nonalcoholic fatty liver diseases (NAFLD) by liver biopsy, and compare with four noninvasive fibrotic biomarker scores (NFS, FIB-4, BARD and APRI).

METHODS

116 NAFLD patients and 23 normal control group were enrolled. The diagnostic performance of 2D-SWE and four noninvasive fibrotic biomarker scores was evaluated based on histopathological inflammation grades and fibrosis stages (F) according to Kleiner/Brunt et al.'s criteria classification. 5-fold cross validation and receiver operating characteristics curve (ROC) analyses were used to obtain an assessment of 2D-SWE and four noninvasive fibrotic biomarker scores; then cross validated area under the curves (AUCs) were compared using the test of Delong. Meanwhile, influence of steatosis on liver stiffness measurement (LSM) of 2D-SWE was also studied.

RESULTS

Liver stiffness measured by 2D-SWE proved to be an excellent diagnostic indicator for detecting steatohepatitis (AUROC =0.88), and fibrosis: ≥F2 stage (AUROC =0.86), ≥F3 stage (AUROC =0.89) and =F4 stage (AUROC =0.90) with the cutoff values were 7.3, 10.0, 11.6 and 12.6 kPa, respectively. Compared with fibrotic scores, 2D-SWE had the highest AUROC for predicting ≥F2, ≥F3, =F4 by Delong test (all P<0.05). No statistic differences of LSM were found among different steatosis levels (P=0.97).

CONCLUSIONS

The stiffness measured by 2D-SWE could be used to noninvasively identify steatohepatitis and stage fibrosis in NAFLD patients. Moreover, the diagnosis efficiency of the stiffness measured by 2D-SWE could not be influenced by steatosis.

Performance of shear wave elastography: A single centre pilot study of mixed etiology liver disease patients with normal BMI

Purpose

To assess the performance of shear wave ultrasound elastography (SWE) for non-invasive grading of fibrosis in normal BMI patients with varied aetiology chronic liver disease.

Method

Prospective SWE liver and spleen stiffness (LS, SS respectively) of 124 patients (94 men, mean age 45.4 ± 12.4 years, mean BMI 19.66 ± 1.49) with CLD of mixed aetiology, who underwent liver biopsy, between January 2019-20 was analysed using receiver operating curve (ROC) and classification analysis regression tree (CART) to determine fibrosis cut-off values and nominal logistical regression to quantify fibrosis.

Results

Of 124 patients, 50 (40%) had non-alcoholic steatohepatitis (NASH), 31 (25%) chronic hepatitis B (CHB) and 43 (35%) alcoholic liver disease (ALD) on biopsy. Overall mean LS and SS of the study population was 11.81 ± 5.9 and 16.88 ± 10.8 kPa, respectively. LS cut-off value <8 kPa was consistent with F0, 9-14 kPa for F1-F2 and >14.9 kPa for F3-F4 fibrosis on biopsy. On application of CART, LS value < 5.3 kPa was discriminative for NASH, 5.32 to <12.64 kPa for CHB, >12.64 kPa for ALD, SS <15.3 kPa was discriminative for NASH, 15.3-30 kPa for CHB and >30 kPa for ALD in our study population.

Conclusion

SWE is a viable non-invasive tool for assessment of liver fibrosis grading in a population of mixed aetiology CLD. LS values in conjunction with SS are promising predictors of F2-F3 fibrosis with potential to discriminate select categories like CHB and NASH in such a population.

Liver shear wave elastography and attenuation imaging coefficient measures: prospective evaluation in healthy children

PURPOSE

Ultrasonographic quantitative measurements enable characterizing the stiffness and viscosity of liver parenchyma. Normal Shear Wave Elastography (SWE) values have been reported in adults and children. The Attenuation Imaging (ATI) coefficient is a measure of local sound energy loss thought to reflect steatosis in adults. The aim of our study was to provide normal SWE and ATI liver values in healthy children.

METHODS

A prospective monocentric study was conducted recruiting 86 children (45 boys and 41 girls) from a single University Hospital between January 2019 and June 2020, having a clinically indicated ultrasound examination, without a known or documented history of liver disease. Examinations were performed using an Aplio i800 (Canon Medical Systems) ultrasound system with an i8CX1 transducer. SWE measurements were obtained using a color map showing an automated measurement area grid overlay. ATI coefficients were generated automatically for each region of interest in the right liver.

RESULTS

Overall median age for the pediatric population was 106 months (1-180 months; SD 49 months). Children were normal weighted. Liver SWE was available for all children. The median liver SWE was 4.6 kPa [3.3-6.6]. ATI yielded valid measurements in 77 patients. The median ATI coefficient was 0.65 [0.5-0.81] dB/cm/MHz. No impact of age, sex, weight and Body Mass Index was observed.

CONCLUSION

SWE and ATI liver values were provided in healthy children. The normative quantitative data might be useful to characterize liver parenchyma in children better.

Diagnostic accuracy of elastography and magnetic resonance imaging in patients with NAFLD: A systematic review and meta-analysis

BACKGROUND AND AIMS

Vibration-controlled transient elastography (VCTE), point shear wave elastography (pSWE), 2-dimensional shear wave elastography (2DSWE), magnetic resonance elastography (MRE), and magnetic resonance imaging (MRI) have been proposed as non-invasive tests for patients with non-alcoholic fatty liver disease (NAFLD). This study evaluated their diagnostic accuracy for liver fibrosis and non-alcoholic steatohepatitis (NASH).

METHODS

PubMED/MEDLINE, EMBASE and the Cochrane Library were searched for studies examining the diagnostic accuracy of these index tests, against histology as the reference standard, in adult patients with NAFLD. Two authors independently screened and assessed methodological quality of studies and extracted data. Summary estimates of sensitivity, specificity and area under the curve (sAUC) were calculated for fibrosis stages and NASH, using a random effects bivariate logit-normal model.

RESULTS

We included 82 studies (14,609 patients). Meta-analysis for diagnosing fibrosis stages was possible in 53 VCTE, 11 MRE, 12 pSWE and 4 2DSWE studies, and for diagnosing NASH in 4 MRE studies. sAUC for diagnosis of significant fibrosis were: 0.83 for VCTE, 0.91 for MRE, 0.86 for pSWE and 0.75 for 2DSWE. sAUC for diagnosis of advanced fibrosis were: 0.85 for VCTE, 0.92 for MRE, 0.89 for pSWE and 0.72 for 2DSWE. sAUC for diagnosis of cirrhosis were: 0.89 for VCTE, 0.90 for MRE, 0.90 for pSWE and 0.88 for 2DSWE. MRE had sAUC of 0.83 for diagnosis of NASH. Three (4%) studies reported intention-to-diagnose analyses and 15 (18%) studies reported diagnostic accuracy against pre-specified cut-offs.

CONCLUSIONS

When elastography index tests are acquired successfully, they have acceptable diagnostic accuracy for advanced fibrosis and cirrhosis. The potential clinical impact of these index tests cannot be assessed fully as intention-to-diagnose analyses and validation of pre-specified thresholds are lacking.

LAY SUMMARY

Non-invasive tests that measure liver stiffness or use magnetic resonance imaging (MRI) have been suggested as alternatives to liver biopsy for assessing the severity of liver scarring (fibrosis) and fatty inflammation (steatohepatitis) in patients with non-alcoholic fatty liver disease (NAFLD). In this study, we summarise the results of previously published studies on how accurately these non-invasive tests can diagnose liver fibrosis and inflammation, using liver biopsy as the reference. We found that some techniques that measure liver stiffness had a good performance for the diagnosis of severe liver scarring.