hepatic and biliary disorders
Laboratory Tests of the Liver and Gallbladder
Tests of Hepatic Synthetic Capacity
PT may be expressed in time (seconds) or, preferably, as a ratio of the patient’s measured PT to the laboratory’s control value (INR—see Testing ). The INR is more accurate than PT for monitoring anticoagulation. PT or INR is a valuable measure of the liver’s ability to synthesize fibrinogen and vitamin K–dependent clotting factors: factors II (prothrombin), VII, IX, and X. Changes can occur rapidly because some of the involved clotting factors have short biologic half-lives (eg, 6 hours for factor VII). Abnormalities indicate severe hepatocellular dysfunction, an ominous sign in acute liver disorders. In chronic liver disorders, an increasing PT or INR indicates progressive liver failure. The PT or INR does not increase in mild hepatocellular dysfunction and is often normal in compensated A prolonged PT and an abnormal INR can result from coagulation disorders such as a Disseminated Intravascular Coagulation (DIC) or Hepatocytes synthesize most serum proteins, including alpha- and beta-globulins,albumin, and most clotting factors (but not factor VIII, produced by the vascular endothelium, or gamma-globulin, produced by B cells). Hepatocytes also make proteins that aid in the diagnosis of specific disorders: Alpha-1 antitrypsin (absent or decreased in Alpha-1 Antitrypsin Deficiency ) Ceruloplasmin (reduced in Wilson Disease ) Transferrin (saturated with iron in Secondary Iron Overload ) Ferritin (greatly increased in Overview of Iron Overload ) These proteins usually increase in response to damage (eg, inflammation) to various tissues, so that elevations may not specifically reflect liver disorders. Conversely, serum levels of these proteins may decrease in Cirrhosis . commonly decreases in chronic liver disorders because of an increase in volume of distribution (eg, due to Ascites ), a decrease in hepatic synthesis, or both. Values Advanced Cirrhosis (the most common cause) Alcohol-Related Liver Disease None Chronic inflammation Protein undernutrition from the kidneys (eg, Overview of Nephrotic Syndrome ), gut (eg, due to protein-losing gastroenteropathies), or skin (eg, due to burns or Becausealbuminhas a half-life of about 20 days, serum levels typically take weeks to increase or decrease, though changes can be rapid in critical illness. 