Point shear wave elastography method for assessing liver stiffness

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≥3and 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,134consecutive 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 47consecutive 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 from0.83(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.