Clinical Chemistry (Liver Function and Porphyrin Formation)

Question 1

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

Question 2

What compound chelates iron and is the immediate precursor of heme formation?

A. Porphobilinogen
B. Protopoiphyrinogen IX
C. Uroporphyrinogen III
D. Protoporphyrin IX

Question 3

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

Question 4

What compound may be detected by observing its orange-red fluorescence in acid solution?

A. Porphobilinogen
B. Uroporphyrinogen
C. Aminolevulinic acid
D. Coproporphyrin

Question 5

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

Question 6

What is the immediate precursor of bilirubin formation?

A. Mesobilirubinogen
B. Verdohemoglobin
C. Urobilinogen
D. Biliverdin

Question 7

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

Question 8

What enzyme catalyzes the conjugation of bilirubin?

A. Leucine aminopeptidase
B. Glucose-6-phosphate dehydrogenase
C. Uridine diphosphate glucuronyltransferase
D. Carbamoyl phosphate synthetase

Question 9

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

Question 10

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

Question 11

What term is used to describe the accumulation of bilirubin in the skin?

A. Jaundice
B. Hemolysis
C. Cholestasis
D. Kernicterus

Question 12

In the condition kernicterus, the abnormal accumulation of bilirubin occurs in what tissue?

A. Brain
B. Liver
C. Kidney
D. Blood

Question 13

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

Question 14

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

Question 15

Which bilirubin fraction is unconjugated and covalently bound to albumin?

A. Alpha
B. Beta
C. Delta
D. Gamma

Question 16

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

Question 17

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

Question 18

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

Question 19

Which of the following reagent systems contains the components sulfanilic acid, hydrochloric acid, and sodium nitrite?

A. Jaffe
B. Zimmerman
C. Diazo
D. Lowry

Question 20

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

Question 21

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

Question 22

What collective term encompasses the reduction products stercobilinogen, urobilinogen, and mesobilirubinogen?

A. Urobilinogen
B. Mesobilirubinogen
C. Urobilin
D. Bilirubin

Question 23

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

Question 24

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

Question 25

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

Question 26

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

Question 27

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

Question 28

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

Question 29

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

Question 30

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

Question 31

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

Question 32

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

Question 33

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

Question 34

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

Question 35

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