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The proportion of AST to ALT in hepatocytes is about 2.5:1, but because AST is removed from serum by the liver sinusoidal cells twice as quickly (serum half-life t 1/2 = 18 hr) compared to ALT (t 1/2 = 36 hr), so the resulting serum levels of AST and ALT are about equal in healthy individuals, resulting in a normal AST/ALT ratio around 1.
Normal ranges for both ALT and AST vary by gender, age, and geography and are roughly 8-40 U/L (0.14-0.67 μkal/L). [4] Mild transaminesemia refers to levels up to 250 U/L. [ 1 ] Drug-induced increases such as that found with the use of anti-tuberculosis agents such as isoniazid are limited typically to below 100 U/L for either ALT or AST.
Alanine transaminase (ALT), also known as alanine aminotransferase (ALT or ALAT), formerly serum glutamate-pyruvate transaminase (GPT) or serum glutamic-pyruvic transaminase (SGPT), is a transaminase enzyme (EC 2.6.1.2) that was first characterized in the mid-1950s by Arthur Karmen and colleagues. [1]
Liver function tests (LFTs or LFs), also referred to as a hepatic panel or liver panel, are groups of blood tests that provide information about the state of a patient's liver. [1] These tests include prothrombin time (PT/INR), activated partial thromboplastin time (aPTT), albumin , bilirubin (direct and indirect), and others.
Serum AST level, serum ALT (alanine transaminase) level, and their ratio (AST/ALT ratio) are commonly measured clinically as biomarkers for liver health. The tests are part of blood panels. The half-life of total AST in the circulation approximates 17 hours and, on average, 87 hours for mitochondrial AST. [4]
AST and ALT blood levels are both elevated, but at less than 300 IU/liter, with an AST:ALT ratio > 2.0, a value rarely seen in other liver diseases. [52] In the United States, 40% of cirrhosis-related deaths are due to alcohol. [33] In non-alcoholic fatty liver disease (NAFLD), fat builds up in the liver and eventually causes scar tissue. [53]
Hy's law is a rule of thumb that a patient is at high risk of a fatal drug-induced liver injury if given a medication that causes hepatocellular injury (not Hepatobiliary injury) with jaundice. [1] The law is based on observations by Hy Zimmerman, a major scholar of drug-induced liver injury.
[27]: 1794 The serum alanine transaminase (ALT) level usually is greater than the aspartate transaminase (AST) level in the nonalcoholic variant and the opposite in alcoholic FLD (AST:ALT more than 2:1). Simple blood tests may help to determine the magnitude of the disease by assessing the degree of liver fibrosis. [28]