Reducing the Number of Measurements in Liver Point Shear-Wave Elastography: Factors that Influence the Number and Reliability of Measurements in Assessment of Liver Fibrosis in Clinical Practice.

Purpose To identify the minimum number of measurements required for the noninvasive assessment of liver fibrosis by using point shear-wave elastography (pSWE) and determine whether the use of a reliability indicator such as interquartile range [IQR]-to-median ratio will affect diagnostic performance. Materials and Methods Ten liver shear-wave velocity (SWV) measurements by pSWE were obtained in 232 participants. Interclass correlation coefficients (ICC) between the median of the first two through the first nine measurements and all 10 measurements were calculated; the minimum number of measurements with ICC greater than 0.95 versus all 10 measurements was determined. The diagnostic performance of the minimum number of measurements and 10 measurements in identifying significant (Ishak stage, ≥3) and severe fibrosis or cirrhosis (Ishak stage, ≥5) was compared by using areas under the receiver operating characteristic curve. These were compared between measurements that demonstrated higher or lower reliability (IQR-to-median ratio of ≤ 30% and IQR-to-median ratio of > 30%, respectively). Results Compared with 10 measurements, a minimum of six SWV measurements was required. The overall area under the curve for diagnosing significant (areas under the receiver operating characteristic curve, 0.828 vs 0.839; P = .487) and severe fibrosis or cirrhosis (0.953 vs 0.969, respectively; P = .145) did not differ according to number of measurements (six vs 10); a median of six measurements resulted in only limited disagreement (nine of 232 [3.9%]) versus histologic evaluation. When using 10 measurements, higher reliability measurements showed a lower percentage of discordance between pSWE and significant fibrosis and severe fibrosis or cirrhosis (22 [14.7%] and three [2.0%] of 150 cases, respectively) compared with lower reliability measurements (26 [31.7%] and eight [9.8%] of 82 cases, respectively). Significant fibrosis was an independent predictor for lower reliability (hazard ratio, 2.22; P < .020). Conclusion A limited number of SWV measurements (median six vs median 10) were required for the assessment of liver fibrosis by using pSWE. The number of measurements had less influence on the diagnostic accuracy compared with lower reliability measurements. RSNA, 2018 Online supplemental material is available for this article.