hepatic and biliary disorders
Laboratory Tests of the Liver and Gallbladder
Other Laboratory Tests
 to be excreted. In patients with portosystemic shunting and chronic liver disease, the diseased liver does not clear ammonia, which then enters the systemic circulation, possibly contributing to Portosystemic Encephalopathy . Elevated ammonia levels occur in hepatic encephalopathy, but levels may be falsely low or high. In advanced liver disorders, the following may increase ammonia levels: High-protein meals Overview of Gastrointestinal Bleeding None Hypokalemia None Metabolic Alkalosis None Certain drugs (eg, alcohol, barbiturates, diuretics, opioids, valproate) High-dose chemotherapy Total Parenteral Nutrition (TPN) None Renal insufficiency Extreme muscle exertion and muscle wasting Aspirin and Other Salicylate Poisoning None Shock None Ureterosigmoidostomy Introduction to Urinary Tract Infections (UTIs) with a urease-producing organism (eg, Because the degree of elevation in the ammonia level correlates poorly with severity of hepatic encephalopathy in chronic liver disease, this level has limited usefulness in monitoring therapy. In acute liver failure, elevated arterial ammonia levels occur due to severe acute hepatocyte dysfunction and/or necrosis, as opposed to portosystemic shunting, and may be a poor prognostic indicator. In chronic liver disorders, serum immunoglobulins often increase. However, elevations are not specific and may not be helpful clinically. Levels increase slightly in acute hepatitis, moderately in chronic active hepatitis, and markedly in autoimmune hepatitis. The pattern of immunoglobulin elevation adds little information, although different immunoglobulins are usually very high in different disorders: IgM in Primary Biliary Cholangitis (PBC) (previously called primary biliary cirrhosis) IgA in Alcohol-Related Liver Disease None IgG in Autoimmune hepatitis and viral hepatitis These heterogeneous antibodies are positive, usually in high titers, in>95% of patients with primary biliary cholangitis. They are also occasionally present in the following: Autoimmune hepatitis Drug-induced hepatitis Other autoimmune disorders, such as connective tissue disorders, myasthenia gravis, autoimmune thyroiditis, Addison disease, and autoimmune hemolytic anemia Antimitochondrial antibodies can help determine the cause of cholestasis because they are usually absent in extrahepatic biliary obstruction and Primary Sclerosing Cholangitis (PSC) . Other antibodies may help in diagnosis of the following: Autoimmune hepatitis: Smooth muscle antibodies against actin, antinuclear antibodies (ANA) that provide a homogeneous (diffuse) fluorescence, and antibodies to liver-kidney microsome type 1 (anti-LKM1) are often present. Primary biliary cholangitis: Antimitochondrial antibody is key to the diagnosis. Primary sclerosing cholangitis: Perinuclear antineutrophil cytoplasmic antibodies (p-ANCA) can help raise the index of suspicion. IgG4 cholangiopathy: Immunoglobulin G4 is frequently elevated. Isolated abnormalities of any of these antibodies are never diagnostic and do not elucidate pathogenesis. 10 to 20 mg/L depending on the laboratory) by the age of 1 year. An increase in AFP, no matter how small, should prompt consideration of primary Hepatocellular Carcinoma (HCC). Serum AFP generally correlates with tumor size, differentiation and metastatic involvement. Because small tumors may produce low levels of AFP, increasing values suggest the presence of HCC, especially when tumors are Mild AFP elevations also occur in acute and chronic hepatitis, probably reflecting liver regeneration; AFP can occasionally increase to 500 ng/mL in Acute Liver Failure . High AFP levels can occur in a few other disorders (eg, embryonic teratocarcinomas, hepatoblastomas in children, some hepatic metastases from gastrointestinal tract cancers, some cholangiocarcinomas), but these circumstances are not common and usually can be differentiated based on clinical and histopathologic grounds. Sensitivity, specificity, and peak levels of AFP in patients with HCC vary by population, reflecting differences in factors such as hepatitis prevalence and ethnicity. In areas with a relatively low prevalence of hepatitis (eg, North America, western Europe). AFP cutoff values of 20 ng/mL to 100 ng/mL (20 mcg/L to 100 mcg/L) have a sensitivity of 61% and a specificity of 86% ( Other laboratory tests reference ). However, not all HCCs produce AFP. Thus, AFP is not an ideal screening test but does have a role in detecting HCC and may be used to monitor response to treatment. Levels exceeding normal ( The degree of hepatic fibrosis can be assessed using multiple noninvasive blood tests. These include tests based on common laboratory results, including AST, ALT, and platelets, such as APRI, FIB4, and Metabolic Dysfunction–Associated Liver Disease (MASLD) (NAFLD) fibrosis score, and proprietary scores, such as FibroTest 1.Zhang J, Chen G, Zhang P, et al: The threshold of alpha-fetoprotein (AFP) for the diagnosis of hepatocellular carcinoma: A systematic review and meta-analysisPLoS One15(2):e0228857, 2020. doi: 10.1371/journal.pone.0228857 