Assessment of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases worldwide. While patients with simple steatosis have excellent long-term prognosis, those with nonalcoholic steatohepatitis (NASH) may progress to cirrhosis, liver failure and hepatocellular carcinoma. NAFLD is also closely associated with metabolic syndrome and cardiovascular events. Therefore, Professor Vincent W.S. Wong，who came from The Chinese University of Hong Kong, Hong Kong SAR, emphasized that the assessment of NAFLD should focus on (1) establishing the diagnosis and ruling out other causes of abnormal liver function tests, (2) identifying patients who have developed or will develop severe liver injury, and (3) detecting important co-morbid illnesses.

He said that the diagnosis of NAFLD is usually straightforward. By ultrasonographic examination, typical features include bright hepatic echotexture (compared with kidney and/or spleen), deep attenuation and vascular blunting. However, chronic hepatitis C can cause hepatic steatosis, and a patient with fatty liver can have alternative causes of abnormal liver function tests. Therefore, the minimal diagnostic workup should include hepatitis B and C serology and anti-nuclear antibody. He also said patients with NASH are more likely to have type 2 diabetes and obesity. Thrombocytopenia, hypoalbuminemia and signs of portal hypertension may be present in patients with NASH-related cirrhosis. However, none of these features are sensitive for NASH or liver fibrosis. Similarly, although serum alanine aminotransferase is commonly used to monitor patients with chronic liver diseases, it has poor correlation with the severity of NAFLD.

Professor Vincent W.S. Wong also pointed out that the gold standard for the diagnosis of NASH and assessment of liver fibrosis is liver biopsy at present. However, the procedure carries a small risk of complications, is expensive and may not be acceptable to many patients. Besides, the problem of sampling error is increasingly recognized. Non-invasive tests for NASH and liver fibrosis are urgently needed. Using six clinical parameters (age, hyperglycemia, body mass index, platelet count,

albumin, and aspartate aminotransferase-to-alanine aminotransferase ratio), the NAFLD fibrosis score has good negative predictive value for advanced fibrosis in both Caucasians and Chinese. Transient elastography by Fibroscan is another promising non-invasive test for liver fibrosis. It appears to have good accuracy in NAFLD, but failed measurement is more common in obese subjects. For the metabolic assessment, anthropometric measurements include body weight, body height,
 
waist circumference and hip circumference. Since Asians have the same percentage of body fat and develop metabolic complications at a lower body mass index than Caucasians, it is important to use ethnic-specific cutoff values in anthropometric measurements. Other essential tests include blood pressure measurement, fasting glucose, and fasting lipids. Impaired glucose tolerance and undiagnosed diabetes are very common among NAFLD patients. Oral glucose tolerance test should be considered in every NAFLD patient, especially if the fasting glucose exceeds 5.6 mmol/L.

Vincent W.S. Wong教授向我们介绍非酒精性脂肪性肝病(NAFLD)是最常见的全球性慢性肝脏疾病之一。单纯脂肪变性的患者预后较好，但非酒精性脂肪性肝炎（NASH）患者可能发展为肝硬化、肝衰竭和肝细胞癌。此外，NAFLD与代谢综合征及心血管事件的发生关系密切。在他的报告中详细说明了NAFLD诊断的金标准、非侵入性诊断方法的应用、NAFLD的危险因素以及并发疾病情况。并通过NAFLD的这些特点总结出对于该疾病评估的重点在于(1)通过相关实验检查诊断并排除其他原因导致的肝脏疾病(2) 判断存在或可能出现严重肝损伤的患者(3) 发现重要的并发疾病。