Non Invasive Assessment of Fibrosis in Non Alcoholic Fatty Liver Disease by Shear Wave Elastography and NAFLD Fibrosis Score: A Cross-sectional Study

Introduction: The major consequence of Non Alcoholic Fatty Liver Disease (NAFLD) is the inflammation and fibrosis of hepatic tissue resulting in cirrhosis, portal hypertension, and eventually hepatocellular carcinoma. Presently, the distinction between simple steatosis, steatohepatitis. and cirrhosis stages of NAFLD is largely dependent on liver biopsy. Since, liver biopsy is invasive, it not suitable for screening purposes. To overcome this limitation, elastography and NAFLD fibrosis score have been studied as non invasive objective substitutes for liver biopsy. Aim: To evaluate the diagnostic accuracy of Shear Wave Elastography (SWE) as a method to diagnose significant-advanced fibrosis in patients with NAFLD by using NAFLD fibrosis score as a reference standard. Materials and Methods: This hospital based cross-sectional study was conducted at JSS Hospital, Mysuru, Karnataka, India over a period of 18 months from September 2018 to November 2019. Total 154 participants underwent ultrasound abdomen to assess the presence and grade the degree of Steatos is. All patients underwent 2D shear wave elastography and the values were compared with NAFLD fibrosis scores. Statistical analysis was performed using Statistical Package for the Social Sciences (SPSS) statistics version 23.0. Results: The age of this study group ranged from 20 to 76 years, mean age was 42.8 +/- 10.8 years including 51 (33.1%) females and 103 (66.9%) males. The level of agreement for assessment of fibrosis between SWE and NAFLD fibrosis score was good (score of 0.71). Using a predictive shear stiffness threshold of 6.1 kPa, shear stiffness distinguished low (fibrosis stage 0-2) from high (fibrosis stage 3-4) fibrosis stages with a sensitivity of 83% and a specificity of 92.7% (area under the curve of 0.879). Conclusion: Two-dimensional shear wave elastography showed a good diagnostic performance for detection of fibrosis.