Kwo Paul Y, Cohen Stanley M, Lim Joseph K
Division of Gastroenterology/Hepatology, Department of Medicine, Stanford University School of Medicine, Palo Alto, California, USA.
Digestive Health Institute, University Hospitals Cleveland Medical Center and Division of Gastroenterology and Liver Disease, Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA.
Am J Gastroenterol. 2017 Jan;112(1):18-35. doi: 10.1038/ajg.2016.517. Epub 2016 Dec 20.
Clinicians are required to assess abnormal liver chemistries on a daily basis. The most common liver chemistries ordered are serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase and bilirubin. These tests should be termed liver chemistries or liver tests. Hepatocellular injury is defined as disproportionate elevation of AST and ALT levels compared with alkaline phosphatase levels. Cholestatic injury is defined as disproportionate elevation of alkaline phosphatase level as compared with AST and ALT levels. The majority of bilirubin circulates as unconjugated bilirubin and an elevated conjugated bilirubin implies hepatocellular disease or cholestasis. Multiple studies have demonstrated that the presence of an elevated ALT has been associated with increased liver-related mortality. A true healthy normal ALT level ranges from 29 to 33 IU/l for males, 19 to 25 IU/l for females and levels above this should be assessed. The degree of elevation of ALT and or AST in the clinical setting helps guide the evaluation. The evaluation of hepatocellular injury includes testing for viral hepatitis A, B, and C, assessment for nonalcoholic fatty liver disease and alcoholic liver disease, screening for hereditary hemochromatosis, autoimmune hepatitis, Wilson's disease, and alpha-1 antitrypsin deficiency. In addition, a history of prescribed and over-the-counter medicines should be sought. For the evaluation of an alkaline phosphatase elevation determined to be of hepatic origin, testing for primary biliary cholangitis and primary sclerosing cholangitis should be undertaken. Total bilirubin elevation can occur in either cholestatic or hepatocellular diseases. Elevated total serum bilirubin levels should be fractionated to direct and indirect bilirubin fractions and an elevated serum conjugated bilirubin implies hepatocellular disease or biliary obstruction in most settings. A liver biopsy may be considered when serologic testing and imaging fails to elucidate a diagnosis, to stage a condition, or when multiple diagnoses are possible.
临床医生需要每天评估肝功能异常情况。最常检测的肝功能指标是血清丙氨酸氨基转移酶（ALT）、天冬氨酸氨基转移酶（AST）、碱性磷酸酶和胆红素。这些检测应称为肝功能指标或肝功能检查。肝细胞损伤定义为AST和ALT水平相对于碱性磷酸酶水平不成比例地升高。胆汁淤积性损伤定义为碱性磷酸酶水平相对于AST和ALT水平不成比例地升高。大多数胆红素以未结合胆红素的形式循环，结合胆红素升高意味着肝细胞疾病或胆汁淤积。多项研究表明，ALT升高与肝脏相关死亡率增加有关。男性真正健康的正常ALT水平范围为29至33 IU/L，女性为19至25 IU/L，高于此水平的应进行评估。临床环境中ALT和/或AST的升高程度有助于指导评估。肝细胞损伤的评估包括检测甲型、乙型和丙型病毒性肝炎，评估非酒精性脂肪性肝病和酒精性肝病，筛查遗传性血色素沉着症、自身免疫性肝炎、威尔逊病和α-1抗胰蛋白酶缺乏症。此外，还应询问处方和非处方药物史。对于确定为肝源性碱性磷酸酶升高的评估，应进行原发性胆汁性胆管炎和原发性硬化性胆管炎的检测。总胆红素升高可发生在胆汁淤积性或肝细胞性疾病中。总血清胆红素水平升高应分为直接胆红素和间接胆红素部分，在大多数情况下，血清结合胆红素升高意味着肝细胞疾病或胆道梗阻。当血清学检测和影像学检查无法明确诊断、对病情进行分期或存在多种可能诊断时，可考虑进行肝活检。
