## 3 Elastographic Methods
### Transient Elastography (TE)
#### 3.1.3 Correlation with Fibrosis Stage and Different Etiologies  
LSM using TE in pediatric patients with chronic liver disease correlated significantly with both fibrosis area fraction [54] and Ishak scores, the correlation appearing better with the latter (r = 0.839 vs. 0.879, \(p\) < 0.0001 for both). LSM discriminated individual stages of fibrosis with high performance. Sensitivity ranged from 81.4% to 100% and specificity ranged from 75.0 to 97.2%. However, LSMs for the same stage of fibrosis varied according to different etiologies. For example, for F3 Ishak stage, higher values were obtained in children with autoimmune hepatitis (16.15 \(\pm\) 7.23 kPa) compared to those with [PERSON]'s disease (8.30 \(\pm\) 0.84 kPa) and hepatitis C virus (HCV) hepatitis (7.43 \(\pm\) 1.73 kPa). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **Factor** & **LSM, kPa** & \begin{tabular}{c} \(p\) \\ **Value** \\ \end{tabular} & \begin{tabular}{c} **No. of** \\ **Children** \\ \end{tabular} & **Study** \\ \hline \multirow{4}{*}{\begin{tabular}{} \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{} \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{} \end{tabular} } & LSM, kPa & \multirow{4}{*}{0.006} & \multirow{2}{*}{51} & [PERSON] et al., \\  & & & 5.96 vs. 6.94 & & & 2016 \\ \cline{1-1} \cline{3-6}  & & vs. 1–5 vs. 1–10 & 6.00 vs. 6.85 vs. & & & & 2016 \\ \cline{1-1} \cline{3-6}  & & vs. 10–17 years & 7.14 vs. 6.97 & & & & 2016 \\ \cline{1-1} \cline{3-6}  & & 0–60 vs. \(\geq\) & 6.61 vs. 5.3 & 0.02 & 40 & [PERSON] et al., 2017 \\ \cline{1-1} \cline{3-6}  & & 6.61 vs. 6.54 & 0.41 & 51 & & 2016 \\ \cline{1-1} \cline{3-6}  & & 5.4 vs. 5.6 & 0.63 & 40 & [PERSON] et al., 2017 \\ \hline \multicolumn{6}{c}{Explanations: LSM: liver stiffness measurement; kPa: kilopascal, SWV: shear wave velocity; N.S non-significant; m/s: meter per second.} \\ \end{tabular} \\ \hline \end{tabular}
\end{table} 
Table 1: Cont. Multiple regression analysis revealed that Ishak fibrosis stage was the only independent variable associated with higher LSM (\(p\) < 0.0001) [17]. In a study that prospectively included 116 consecutive children with chronic liver diseases, [PERSON] et al. reported that the AUROCs for the diagnosis of cirrhosis were 0.88, 0.73, and 0.73 for FibroScan, Fibrotest, and Aspartateaminotransferase-to-Platelet Ratio Index (APRI), respectively. The FibroScan equipped with the specific smaller diameter probe (S-probe 5 mm) could become a useful tool for the management of chronic liver diseases in children [49]. In a pediatric cohort, TE findings were compared with the ability of serum hyaluronic acid (HA) and human cartilage glycoprotein-39 (YKL-40) values in predicting advanced hepatic fibrosis [55]. For the prediction of advanced fibrosis, TE showed an AUROC significantly higher (0.83) than HA (0.72) or YKL-40 (0.52). The optimal TE cut-off value for predicting F3-F4 fibrosis was 8.6 kPa. The combination of TE and HA was not better than TE alone for predicting advanced fibrosis [56]. Studies in adults have shown that inflammation increases liver stiffness, leading to an overestimation of fibrosis. The influence of inflammation to LSMs in children/young adults has been investigated as well. In patients with fibrosis stages F0-F2, the proportion of those with LSM > 8.6 kPa increased with increasing alanine aminotransferase (ALT). In patients with F3-F4, there was no association between ALT and LSM. A weak correlation between a change in ALT and LSM was observed in patients with no/minimal fibrosis and inflammatory liver diseases (r = 0.33). In children with no/minimal hepatic fibrosis and inflammatory liver disease, high ALT values were associated with LSM in the range typical for advanced fibrosis. However, with more advanced fibrosis, inflammation did not appear to contribute to LSM. Caution must be taken when interpreting LSM for assessing fibrosis severity in the setting of inflammation [11]. TE may be useful in follow-up of children following Fontan surgery.