Accuracy of Ultrasound Elastography and Fibrosis-4 Index (FIB-4) in Ruling Out Cirrhosis in Obese Non-Alcoholic Fatty Liver Disease (NAFLD) Patients

Introduction: Non-alcoholic fatty liver disease (NAFLD) is the most common cause of advanced liver disease in the USA. Liver biopsy, the gold standard diagnostic test for evaluating liver fibrosis, is associated with significant risk and expense. The accuracy of ultrasound elastography and Fibrosis-4 index (FIB-4) in the obese NAFLD population is unknown. We aimed to compare the accuracy of ultrasound elastography and FIB-4 to liver biopsy in ruling out cirrhosis in NAFLD patients at a tertiary, transplant referral center in the US. Methods: We retrospectively evaluated 93 patients with a mean age of 53 years (SD: 13 years) who underwent liver ultrasound elastography and liver biopsy, and additionally calculated their FIB-4 at the time of biopsy. We compared the liver stiffness measurement (LSM) obtained from ultrasound elastography and FIB-4 with the pathology results for ruling out cirrhosis. Results: 85% of the patients were white, 53% were female, average BMI was 34.7 (SD: 6.7), 52% had diabetes, and 53% had hypertension. For biopsy-proven cirrhosis (prevalence 15%), a cut-off value of 12.5 kilopascals (kPa) for F4 had a sensitivity of 92% and a specificity of 54%. Values below this threshold excluded cirrhosis with 98% certainty. Compared to FIB-4, ultrasound elastography showed higher accuracy in ruling out cirrhosis (92% vs. 80% sensitivity, 98% vs. 95% negative predictive value (NPV), respectively). Conclusion: To our knowledge, this is the first study in a tertiary transplant referral center in the USA to show that ultrasound elastography was superior to FIB-4 and can be used as a reliable screening test to rule out cirrhosis in obese NAFLD patients at a 12.5 kPa cut-off. Therefore, helping to avoid the risk and expense associated with liver biopsy.