Purpose or Case Report: Ultrasound shear wave elastography (US SWE) can be used to noninvasively measure liver stiffness. US SWE is a potentially useful technique for diagnosing and monitoring liver fibrosis, obviating the need for liver biopsy in some patients. When compared to MR elastography (MRE), US SWE is lower cost, portable, and does not need sedation/anesthesia. US SWE measurements can vary by method (point vs. 2D) and vendor. Few studies have defined cut-off values for detecting fibrosis in pediatric patients using US 2D SWE. This study aims to evaluate the diagnostic performance and define cut-off values of US 2D SWE for the detection of liver fibrosis in pediatric patients, using Toshiba (Canon) Aplio 500 and Aplio i800 systems.
Methods & Materials: This was an IRB-approved, retrospective study. We searched electronic medical records to identify patients (<20 years-old) that had undergone both liver US 2D SWE and percutaneous biopsy within a 6-month interval. Liver biopsies were histologically assessed using the METAVIR (fibrosis) and NASH Clinical Research Network (steatosis) scoring systems. Continuous data were compared using the Mann-Whitney U test. Receiver operating characteristic (ROC) curve analysis was used to evaluate diagnostic performance.
Results: 48 patients were included in our study, with a median age of 12.5 years (interquartile range, 8.0-15.8 years). 25 patients were male (52.1%). There were 29 patients with METAVIR fibrosis score of F0-1 and 19 patients with a score of F2-4. Median liver shear wave speed (SWS) was significantly lower in patients with stage F0-1 fibrosis compared to patients with stage F2-4 fibrosis (1.64 vs. 2.11 m/s; p=0.003). For differentiating METAVIR stages 0-1 from stage 2 or higher fibrosis based on SWS, the AUC was 0.75 (95% CI: 0.61-0.86). A cut-off of >1.88 m/s yielded sensitivity of 73.7% (95% CI: 48.8-90.9) and specificity of 79.3% (95% CI: 60.3.7-92.0). For the subpopulation of patients without significant hepatic steatosis on histology (n=35), the AUC was 0.86 (95% CI: 0.70-0.95) for the same distinction. In this subpopulation, a cut-off of >1.88 m/s yielded a sensitivity of 80.0% (95% CI: 51.9-95.7) and specificity of 95.0% (95% CI 75.1-99.9).
Conclusions: US 2D SWE distinguishes patients with no/mild fibrosis from those with moderate/severe fibrosis with good sensitivity and specificity. Diagnostic performance is comparable to that published for MRE and is likely adversely impacted by the presence of steatosis.