Bidimensional shear-wave elastography for assessing liver fibrosis in children: a proposal of reference values that correlate with the histopathological Knodell-Ishak score.

BACKGROUND

A limited number of publications correlate bidimensional shear-wave elastography (2-D SWE) and stages of liver fibrosis in children.

OBJECTIVE

To correlate liver elastography values using 2-D SWE and liver biopsy classified by Knodell-Ishak score to evaluate fibrosis in pediatric patients with liver disease, and to propose values of 2-D SWE (kPa) correlating with Knodell-Ishak score, which have not been defined in the literature.

MATERIALS AND METHODS

We conducted a prospective cross-sectional observational study on the performance of diagnostic tests. Between June 2016 and June 2018, elastography was performed in 213 children and young adults who had undergone liver biopsy. B mode, Doppler and 2-D SWE were performed using an Aixplorer (SuperSonic Imagine, Aix-en-Provence, France). Histology samples were classified using the Knodell-Ishak score. We evaluated performance by assessing sensitivity, specificity, positive predictive value and negative predictive value. To determine cut-off points for the continuous variables, we used receiver operating characteristic (ROC) curves. All the cutoff values we established apply only to the SuperSonic Aixplorer system.

RESULTS

Measurement with 2-D SWE was successful, with a good correlation with fibrosis stage. The area under the curve (AUC) to differentiate between early (Stages 1-2) and moderate (Stages 3-4) fibrosis was 0.91 (95% confidence interval [CI]: 0.87-0.96), with a sensitivity of 92% and specificity of 86%, with a cutoff value 12 kPa (2 m/s). The AUC of severe fibrosis (early stages of cirrhosis; Stage 5) was 0.95 (95% CI: 0.92-0.97), with a sensitivity of 94% and specificity of 90%, with a cutoff value 18.5 kPa (2.48 m/s). In two patients with hematopoietic stem cell transplantation and suspicion of graft versus host disease we found high 2-D SWE values in correlation with the fibrosis stages (Stage 0 with a median of 13 kPa [2.08 m/s] with hemosiderosis Grade 2 in one child and Stage 2 with a median of 46 kPa [3.91 m/s] and hemosiderosis Grade 4 in the other).

CONCLUSION

Our study shows the usefulness and accuracy of 2-D SWE for detecting liver fibrosis in pediatric patients. We propose reference values for Knodell-Ishak Stages 1 and 5. We found hemosiderosis as a possible confounding factor that hasn't been described with 2-D SWE.