Observational Study
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World J Gastroenterol. Apr 28, 2014; 20(16): 4787-4796
Published online Apr 28, 2014. doi: 10.3748/wjg.v20.i16.4787
Point shear wave elastography method for assessing liver stiffness
Giovanna Ferraioli, Carmine Tinelli, Raffaella Lissandrin, Mabel Zicchetti, Barbara Dal Bello, Gaetano Filice, Carlo Filice
Giovanna Ferraioli, Raffaella Lissandrin, Mabel Zicchetti, Gaetano Filice, Carlo Filice, Department of Infectious Diseases, Fondazione IRCCS Policlinico San Matteo, Medical School University of Pavia, 27100 Pavia, Italy
Carmine Tinelli, Clinical Epidemiology and Biometric Unit, Fondazione IRCCS Policlinico San Matteo, 27100 Pavia, Italy
Barbara Dal Bello, Department of Pathology, Fondazione IRCCS Policlinico San Matteo, 27100 Pavia, Italy
Author contributions: Ferraioli G and Tinelli C contributed equally to this work; Ferraioli G, Tinelli C and Filice C designed the research; Ferraioli G, Lissandrin R, Zicchetti M and Dal Bello B performed the research; Tinelli C analyzed the data; Ferraioli G, Zicchetti M and Lissandrin R wrote the manuscript; Tinelli C, Dal Bello B, Filice G and Filice C reviewed the manuscript; and Ferraioli G, Tinelli C, Dal Bello B, Zicchetti M, Lissandrin R, Filice G and Filice C approved the final version of the manuscript; all the authors of the Liver Fibrosis Study Group performed the research, reviewed the manuscript and approved the final version.
Supported by The FibroScan device was made available for this study by Echosens (Paris, France), and the iU22 ultrasound equipment was provided by Philips Medical Systems (Bothell, WA, United States)
Correspondence to: Giovanna Ferraioli, MD, Researcher, Ultrasound Unit, Department of Infectious Diseases, Fondazione IRCCS Policlinico San Matteo, Medical School University of Pavia, Via Taramelli 5, 27100 Pavia, Italy. giovanna.ferraioli@unipv.it
Telephone: +39-382-502887 Fax: +39-382-501505
Received: January 13, 2014
Revised: February 9, 2014
Accepted: March 8, 2014
Published online: April 28, 2014
Processing time: 105 Days and 15.9 Hours
Abstract

AIM: To estimate the validity of the point shear-wave elastography method by evaluating its reproducibility and accuracy for assessing liver stiffness.

METHODS: This was a single-center, cross-sectional study. Consecutive patients with chronic viral hepatitis scheduled for liver biopsy (LB) (Group 1) and healthy volunteers (Group 2) were studied. In each subject 10 consecutive point shear-wave elastography (PSWE) measurements were performed using the iU22 ultrasound system (Philips Medical Systems, Bothell, WA, United States). Patients in Group 1 underwent PSWE, transient elastography (TE) using FibroScan (Echosens, Paris, France) and ultrasound-assisted LB. For the assessment of PSWE reproducibility two expert raters (rater 1 and rater 2) independently performed the examinations. The performance of PSWE was compared to that of TE using LB as a reference standard. Fibrosis was staged according to the METAVIR scoring system. Receiver operating characteristic curve analyses were performed to calculate the area under the receiver operating characteristic curve (AUC) for F≥ 2, F≥ 3 and F = 4. The intraobserver and interobserver reproducibility of PSWE were assessed by calculating Lin’s concordance correlation coefficient.

RESULTS: To assess the performance of PSWE, 134 consecutive patients in Group 1 were studied. The median values of PSWE and TE (in kilopascals) were 4.7 (IQR = 3.8-5.4) and 5.5 (IQR = 4.7-6.5), respectively, in patients at the F0-F1 stage and 3.5 (IQR = 3.2-4.0) and 4.4 (IQR = 3.5-4.9), respectively, in the healthy volunteers in Group 2 (P < 10-5). In the univariate analysis, the PSWE and TE values showed a high correlation with the fibrosis stage; low correlations with the degree of necroinflammation, aspartate aminotransferase and gamma-glutamyl transferase (GGT); and a moderate negative correlation with the platelet count. A multiple regression analysis confirmed the correlations of both PSWE and TE with fibrosis stage and GGT but not with any other variables. The following AUC values were found: 0.80 (0.71-0.87) for PSWE and 0.82 (0.73-0.89) for TE (P = 0.42); 0.88 (0.80-0.94) for PSWE and 0.95 (0.88-0.98) for TE (P = 0.06); and 0.95 (0.89-0.99) for PSWE and 0.92 (0.85-0.97) for TE (P = 0.30) for F≥ 2, F≥ 3 and F = 4, respectively. To assess PSWE reproducibility, 116 subjects were studied, including 47 consecutive patients scheduled for LB (Group 1) and 69 consecutive healthy volunteers (Group 2). The intraobserver agreement ranged from 0.83 (95%CI: 0.79-0.88) to 0.96 (95%CI: 0.95-0.97) for rater 1 and from 0.84 (95%CI: 0.79-0.88) to 0.96 (95%CI: 0.95-0.97) for rater 2. The interobserver agreement yielded values from 0.83 (95%CI: 0.78-0.88) to 0.93 (95%CI: 0.91-0.95).

CONCLUSION: PSWE is a reproducible method for assessing liver stiffness, and it compares with TE. Compared with patients with nonsignificant fibrosis, healthy volunteers showed significantly lower values.

Keywords: Chronic viral hepatitis; Liver biopsy; Liver fibrosis; Ultrasound; Elastography; Sensitivity and specificity

Core tip: The results of this study show that point shear-wave elastography (PSWE) is a highly reproducible method for assessing liver stiffness that is characterized by high levels of intraobserver and interobserver agreement, both overall and for single measurements. The PSWE performance compares with that of transient elastography (TE), the most widely accepted method for the noninvasive assessment of liver fibrosis. Compared with TE, routine ultrasound with elastography is advantageous because it allows the evaluation of other parameters that are complementary to stiffness, is highly accurate for the diagnosis of cirrhosis and can be used to screen for focal liver lesions.