These non-invasive methods can be used for NAFLD screening but are not accepted as a substitute for liver biopsy in NAFLD nor NASH clinical trials, as only a liver biopsy can define liver pathology.Ultrasound presented average sensitivity and specificity for diagnosing the disease in children, while in the adult population, sensitivity and specificity were significantly higher. Proton density fat fraction magnetic resonance imaging has been increasingly used for the diagnosis of steatosis in pediatric patients. Elastography is an effective tool for staging liver fibrosis and discriminating NASH from NAFLD in children.CT scans and MRIs are more accurate in detecting cirrhosis than conventional ultrasound. Transient elastography is recommended for the initial assessment of liver fibrosis and cirrhosis and helps to predict complications and prognosis, but the interpretation of results is carefully weighed in the presence of limiting factors, such as steatosis, high BMI, lower degrees of hepatic fibrosis and narrow spaces between the ribs (intercostal spaces). However, transient elastography can fail for people with pre-hepatic portal hypertension. Transient elastography is not considered to be a replacement for liver biopsy.Magnetic resonance elastography (MRE) is an emerging method that can accurately assess hepatic fibrosis and is recommended by the APASL. MRE possesses a good sensitivity to quantify hepatic fat and excellent accuracy to detect fibrosis in NAFLD regardless of BMI and inflammation and is suggested as a more reliable alternative to diagnose NAFLD and its progression to NASH compared to ultrasound and blood tests.
Low thyroid activity is more prevalent in people with NASH, which would be detected by determining the thyroid-stimulating hormone. Some biomarker-based blood tests have been developed and may be useful for diagnosis.Although blood tests cannot diagnose NAFLD, circulating serum biomarkers of liver fibrosis can give moderate estimates in the diagnosis of liver fibrosis and cirrhosis. The ratio of the transaminase liver enzyme aspartate aminotransferase (AST) to platelets in the blood, known as the AST/platelet ratio index (APRI score), and Fibrotest are recommended as the preferred noninvasive tests for cirrhosis by the Asian-Pacific Association for Study of the Liver (APASL). Several other scores such as FIB-4 score and NAFLD fibrosis score can also reflect the burden of the fibrosis in the liver, and previous studies have confirmed that these score can predict future development of mortality and liver cancer. Imaging
A liver ultrasound scan or magnetic resonance imaging (MRI) can diagnose steatosis, but not fibrosis and confirmation of early cirrhosis detection by ultrasound by other diagnostic methods is recommended. The European Association for the Study of the Liver (EASL) recommends screening for steatosis whenever NAFLD is suspected as this is a strong predictor of the disease evolution and predicts future type 2 diabetes, cardiovascular events, and hypertension.