Clinical Chemistry (Liver Function and Porphyrin Formation) Flashcards
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Which compounds originally condense to form aminolevulinic acid?
A. Oxoglutarate and aspartate
B. Isocitrate and coenzyme II
C. Oxalacetate and malate
D. Succinyl coenzyme A and glycine
What compound chelates iron and is the immediate precursor of heme formation?
A. Porphobilinogen
B. Protopoiphyrinogen IX
C. Uroporphyrinogen III
D. Protoporphyrin IX
Which of the following is a qualitative screening test for porphobilinogen that may be performed to aid in the diagnosis of the porphyrias?
A. Caraway test
B. Gutmantest
C. Jendrassik-Grof test
D. Watson-Schwartz test
What compound may be detected by observing its orange-red fluorescence in acid solution?
A. Porphobilinogen
B. Uroporphyrinogen
C. Aminolevulinic acid
D. Coproporphyrin
The laboratory receives a request that assays for urinary aminolevulinic acid, porphobilinogen, uroporphyrin, and coproporphyrin are to be performed on a patient. Which of the following will not contribute to the integrity of the sample when these assays are performed on the same urine specimen?
A. Refrigeration
B. Addition of hydrochloric acid
C. 24-hour urine collection
D. Use of a brown bottle
What is the immediate precursor of bilirubin formation?
A. Mesobilirubinogen
B. Verdohemoglobin
C. Urobilinogen
D. Biliverdin
To quantify serum bilirubin levels, it is necessary that bilirubin couples with diazotized sulfanilic acid to form what complex?
A. Verdobilirubin
B. Azobilirubin
C. Azobilirubinogen
D. Bilirubin glucuronide
What enzyme catalyzes the conjugation of bilirubin?
A. Leucine aminopeptidase
B. Glucose-6-phosphate dehydrogenase
C. Uridine diphosphate glucuronyltransferase
D. Carbamoyl phosphate synthetase
What breakdown product of bilirubin metabolism is produced in the colon from the oxidation of urobilinogen by microorganisms?
A. Porphobilinogen
B. Urobilin
C. Stercobilinogen
D. Protoporphyrin
Which of the following functions as a transport protein for bilirubin in the blood?
A. Albumin
B. Alpha1-globulin
C. Beta-globulin
D. Gamma-globulin
What term is used to describe the accumulation of bilirubin in the skin?
A. Jaundice
B. Hemolysis
C. Cholestasis
D. Kernicterus
In the condition kernicterus, the abnormal accumulation of bilirubin occurs in what tissue?
A. Brain
B. Liver
C. Kidney
D. Blood
As a reduction product of bilirubin catabolism, this compound is partially reabsorbed from the intestine through the portal circulation for reexcretion by the liver. What is this compound?
A. Verdohemoglobin
B. Urobilinogen
C. Urobilin
D. Biliverdin
Which of the following factors will not adversely affect the accurate quantification of bilirubin in serum?
A. Lipemia
B. Hemolysis
C. Exposure to light
D. Specimen refrigeration
Which bilirubin fraction is unconjugated and covalently bound to albumin?
A. Alpha
B. Beta
C. Delta
D. Gamma
As the red blood cells disintegrate, hemoglobin is released and converted to the pigment bilirubin. Which organ is primarily responsible for this function?
A. Spleen
B. Kidneys
C. Intestines
D. Liver
Which of the following methods is not used for the quantification of serum bilirubin?
A. Bilirubinometer
B. Jendrassik and Grof
C. Zimmerman
D. Bilirubin oxidase
Which of the following does not accurately describe direct bilirubin?
A. Insoluble in water
B. Conjugated in the liver
C. Conjugated with glucuronic acid
D. Excreted in the urine of jaundiced patients
Which of the following reagent systems contains the components sulfanilic acid, hydrochloric acid, and sodium nitrite?
A. Jaffe
B. Zimmerman
C. Diazo
D. Lowry
Indirect-reacting bilirubin may be quantified by reacting it initially in which reagent?
A. Dilute hydrochloric acid
B. Dilute sulfuric acid
C. Caffeine-sodium benzoate
D. Sodium hydroxide
Which of the following methods employs a reaction where bilirubin is oxidized to colorless biliverdin?
A. Bilirubinometer
B. Bilirubin oxidase
C. High-performance liquid chromatography
D. Jendrassik-Grof
What collective term encompasses the reduction products stercobilinogen, urobilinogen, and mesobilirubinogen?
A. Urobilinogen
B. Mesobilirubinogen
C. Urobilin
D. Bilirubin
What condition is characterized by an elevation of total bilirubin primarily due to an increase in the conjugated bilirubin fraction?
A. Hemolytic jaundice
B. Neonatal jaundice
C. Crigler-Najjar syndrome
D. Obstructive jaundice
Which of the following is characteristic of hemolytic jaundice?
A. Unconjugated serum bilirubin level increased
B. Urinary bilirubin level increased
C. Urinary urobilinogen level decreased
D. Fecal urobilin level decreased
What may be the cause of neonatal physiological jaundice of the hepatic type?
A. Hemolytic episode caused by an ABO incompatibility
B. Stricture of the common bile duct
C. Hemolytic episode caused by an Rh incompatibility
D. Deficiency in the bilirubin conjugation enzyme system
Which of the following laboratory results is not characteristic of a complete obstruction of the common bile duct?
A. Negative urine urobilinogen
B. Negative fecal urobilinogen and urobilin
C. Negative urine bilirubin
D. Excretion of a pale-colored stool
Which of the following characterizes hepatic dysfunction in the early stage of viral hepatitis?
A. Elevation in urobilinogen and urobilin excretion in the feces
B. Elevation in the serum unconjugated bilirubin fraction
C. Depression in the serum conjugated bilirubin fraction
D. Depression in urinary urobilinogen excretion
Which of the following characterizes Crigler-Najjar syndrome?
A. Inability to transport bilirubin from the sinusoidal membrane to the microsomal region
B. Deficiency of the enzyme system required for conjugation of bilirubin
C. Inability to transport bilirubin glucuronides to the bile canaliculi
D. Severe liver cell damage accompanied by necrosis
Which of the following disorders is characterized by an inability to transport bilirubin from the sinusoidal membrane into the hepatocyte?
A. Carcinoma of the common bile duct
B. Crigler-Najjar syndrome
C. Dubin-Johnson syndrome
D. Gilbert syndrome
Which of the following is not characteristic of Dubin-Johnson syndrome?
A. Impaired excretion of bilirubin into the bile
B. Hepatic uptake of bilirubin is normal
C. Inability to conjugate bilirubin
D. Increased level of bilirubin in urine
Which of the following disorders is not a form of hepatic jaundice?
A. Cirrhosis
B. Crigler-Najjar syndrome
C. Hepatitis
D. Neoplasm of common bile duct
Which of the following disorders can be classified as a form of prehepatic jaundice?
A. Acute hemolytic anemia
B. Cirrhosis
C. Dubin-Johnson syndrome
D. Neoplasm of common bile duct
The following laboratory results are
determined on a patient with a suggested
diagnosis of biliary obstruction:
Serum total bilirubin—increased
Serum conjugated bilirubin—normal
Urine bilirubin—increased
Fecal urobilin—decreased
Which laboratory result is the least
consistent with such a diagnosis?
A. Serum total bilirubin
B. Serum conjugated bilirubin
C. Urine bilirubin
D. Fecal urobilin
A 42-year-old woman is admitted to the hospital with complaints of abdominal pain and inability to eat, which have gotten worse during the past several weeks. Although the pain had been uncomfortable, what alarmed her was noticing a slight yellow color in her eyes. Blood was drawn and the test results follow: total bilirubin 3.9 mg/dL, direct bilirubin 2.7 mg/dL, AST slightly elevated (3 times the upper limit of the reference range), ALT slightly elevated (3 times the upper limit of the reference range), alkaline phosphatase markedly elevated (6 times the upper limit of the reference range), and urine urobilinogen decreased. What diagnosis do these test results support?
A. Viral hepatitis
B. Cirrhosis
C. Exposure to toxic chemicals
D. Biliary obstruction
Which of the following results is least consistent with a diagnosis of viral hepatitis?
A. Seaim total bilirubin 7.5 mg/dL, direct bilirubin 5.5 mg/dL, indirect bilirubin 2.0 mg/dL
B. Urine urobilinogen increased
C. AST increased 10 times the upper limit of the reference range
D. ALT increased 13 times the upper limit of the reference range