Transient elastography with controlled attenuation parameter versus 2D-shear wave elastography with attenuation imaging for the evaluation of hepatic steatosis and fibrosis in NAFLD

Question

1. How does 2D-SWE with ATI compare to TE with CAP?

2. What criteria were used for patient enrollment in the previous NAFLD cohort study?

3. What is the measurement protocol for 2D-SWE and ATI?

4. What technology does FibroScan use to measure liver stiffness and attenuation?

Accepted Answer

2D-SWE with ATI has theoretical advantages over TE with CAP, including easy incorporation into routine B-mode US examinations and accurate selection of the measurement region of interest (ROI) guided by simultaneously provided B-mode images. However, it is unclear whether these theoretical advantages translate into improved diagnostic performance in assessing liver fibrosis and hepatic steatosis compared to TE with CAP. Therefore, a study was conducted to compare CAP with ATI in the diagnosis of steatosis and to compare TE with 2D-SWE in the diagnosis of fibrosis in a NAFLD patient cohort. The results of this study will provide valuable insights into the potential benefits of using 2D-SWE with ATI over TE with CAP in the diagnosis of liver fibrosis and hepatic steatosis in NAFLD patients.

Accepted Answer

In the previous NAFLD cohort study, patients with elevated liver enzymes or clinical suspicion of NASH were enrolled using specific criteria. These criteria included no history of positivity for hepatitis B virus surface antigen, antihepatitis C virus, hepatitis C virus RNA, and hepatitis B virus DNA. Additionally, patients with excessive alcohol consumption greater than the recommended limit (>14 UK units/wk for women and >21 UK units/wk for men) were excluded. Patients with liver pathology other than NAFLD on histopathologic examinations were also excluded. Potential living liver donors who underwent liver biopsy for NAFLD evaluation were enrolled if they met the inclusion criteria of having available results of TE with CAP and reliable LS measurement results obtained from TE.

Accepted Answer

The measurement protocol for 2D-SWE and ATI involves five abdominal radiologists from five institutions establishing a unified method. US examinations are performed using Aplio i800 scanners with a 1-8-MHz convex probe. Participants fast for at least 6 hours before the examination. The liver biopsy is performed in the right anterior section, avoiding reverberation artifacts. A sample box of 2D-SWE measuring 1.5x1.5 cm is placed on the liver parenchyma, and a 1-cm circular measurement ROI is used to obtain the LS value. The LS values are measured 10 times, and the median value is used for analysis. The 2D-SWE measurements are considered reliable if the IQR/median value is less than 30%. After 2D-SWE evaluation, ATI is performed in the right hepatic lobe through the intercostal window. A 2x4-cm square measurement ROI is placed in the sample box, avoiding areas of reverberation artifacts or large hepatic vessels. The attenuation coefficient (AC) in dB/cm/MHz is measured five times, and the median value is used. An R-value of 0.80 or higher indicates a reliable measurement.

Accepted Answer

FibroScan uses vibration-controlled TE technology to simultaneously measure liver stiffness (LS) and attenuation (CAP). The CAP was designed to measure liver US attenuation at 3.5 MHz on both M and XL probes on signals acquired by FibroScan. CAP and LS measurements were expressed as dB/m and kPa, respectively. LS measurements were considered reliable if the IQR/median value was less than 30%, according to the liver elastography guidelines originally developed for TE [30, 31].

Accepted Answer

In the evaluation of liver pathology in NAFLD, two staining techniques are used: hematoxylin/eosin and Masson trichrome staining. Hematoxylin/eosin staining is a commonly used technique for general tissue examination, providing information about the cellular and tissue structure. Masson trichrome staining, on the other hand, is specifically used to assess fibrosis in the liver. It stains collagen fibers blue, allowing for the visualization and quantification of fibrotic tissue. These staining techniques, when combined with histopathologic evaluation, provide valuable insights into the pathology and fibrosis of NAFLD.

Accepted Answer

For univariate analysis, continuous variables were compared using the Mann-Whitney U test, and categorical variables were compared using the Fisher exact test. These tests help determine significant determinant factors for AC from ATI, LS values from 2D-SWE, CAP from TE, and LS values from TE. Variables with a P-value less than 0.05 in the univariate analysis were included in the multivariate analysis. This approach allows researchers to identify the most influential factors in their study.

Accepted Answer

The final study included 105 participants. This number was obtained by excluding 27 participants who were either excluded due to the absence of an available TE examination or had unreliable measurement results of TE. The remaining participants were potential living liver donors, and detailed information regarding the enrollment process is provided in the Supplementary Material 1. The baseline characteristics of these participants are summarized in Table 1.

Accepted Answer

In the evaluation of hepatic steatosis using CAP and attenuation coefficient, the degree of hepatic steatosis, patients' age, and body mass index (BMI) were found to significantly affect CAP values from TE. Additionally, the grade of hepatic steatosis was the only significant factor affecting AC from ATI. The distribution of hepatic steatosis grades was S0 (32.4%), S1 (39.0%), S2 (21.0%), and S3 (7.6%). The diagnostic performance for detecting each grade of hepatic steatosis using ROC analysis showed varying AUROC values, with the highest being 0.94 for >=F1 and the lowest being 0.89 for >=F4. The AUROC values for detecting liver fibrosis stages using LS from TE and 2D-SWE were also provided, with no significant difference between the two methods in detecting any stage of liver fibrosis.

Transient elastography with controlled attenuation parameter versus 2D-shear wave elastography with attenuation imaging for the evaluation of hepatic steatosis and fibrosis in NAFLD

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Most frequently asked questions

1. How does 2D-SWE with ATI compare to TE with CAP?

2. What criteria were used for patient enrollment in the previous NAFLD cohort study?

3. What is the measurement protocol for 2D-SWE and ATI?

4. What technology does FibroScan use to measure liver stiffness and attenuation?

5. What staining techniques are used for evaluating liver pathology in NAFLD?

6. What statistical tests were used for univariate analysis?

7. What was the total number of participants in the final study?

8. What factors affect CAP from TE and AC from ATI in hepatic steatosis evaluation?

Citations

WFUMB Guidelines/Guidance on Liver Multiparametric Ultrasound. Part 2: Guidance on Liver Fat Quantification.

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Serum vitamin D is associated with ultrasound-defined hepatic fibrosis

Experience in the use of dispersion and shear waves in patients after liver transplantation

References

Design and validation of a histological scoring system for nonalcoholic fatty liver disease

Global epidemiology of nonalcoholic fatty liver disease—Meta‐analytic assessment of prevalence, incidence, and outcomes

Hematological Problems in Pediatric Intensive Care

Liver Fibrosis, but No Other Histologic Features, Is Associated With Long-term Outcomes of Patients With Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease: From steatosis to cirrhosis

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