1. Which one of the following laboratory tests, when elevated, is more likely indicative of biliary tract disease rather than hepatocellular disease?
A. Aspartate aminotransferase (AST)
B. Lactate dehydrogenase (LD)
C. Alkaline phosphatase (ALP)
D. Alanine aminotransferase (ALT)
The correct answer is C. Alkaline phosphatase is associated with the plasma membrane of the hepatocytes which are adjacent to the biliary canaliculi. An increased concentration of alkaline phosphatase occurs in the circulation when there is obstruction or inflammation of the biliary tract. It should also be noted, however, that LD is not favored for routine evaluation of hepatocellular disease because this enzyme is released with cell injury from many different tissues.
2. Which one of the following laboratory tests, when elevated, is more likely indicative of hepatocellular disease rather than biliary tract disease?
A. Alanine aminotransferase (ALT)
B. γ-Glutamyltransferase (GGT)
C. 5′-Nucleotidase (5′-NT)
D. Alkaline phosphatase (ALP)
The correct answer is A. Choices B, C, and D are all tests indicative of biliary tract disease. Elevations in alkaline phosphatase can occur for many reasons other than biliary tract disease. Therefore, it is common to select the GGT and/or 5′-NT along with the alkaline phosphatase in the assessment for biliary tract disease.
3. Which of the following represents a chronic cause, rather than an acute cause, of hepatocellular disease?
C. Toxic injury from excess acetaminophen intake
D. Thrombosis in vessels leading to or exiting the liver
The correct answer is A. Hemochromatosis is an inborn error that leads to hepatocellular disease which progresses over time. All of the other choices produce hepatocellular disease abruptly, and, therefore, represent acute causes of damage to the liver.
4. Bilirubin in the circulation is predominantly derived from which compound below?
A. Myoglobin in the muscle
B. Hemoglobin in red blood cells
C. Transferrin in the liver
D. Iron in the red blood cells
The correct answer is B. Bilirubin is derived from myoglobin in the muscle but to a much lesser extent than from hemoglobin in red blood cells. Senescent red blood cells are destroyed in macrophages, primarily in the spleen, and within the phagocytes, hemoglobin is metabolized to ...