(4) II. TEST FOR CONJUGATION & EXCRETION FUNCTION

Question 1

• Principal pigment in bile
• End product of hgb metabolism (85% is from heme)
• Waste product so there is no physiologic fxn.
• Also formed from destruction of heme-containing proteins such as myoglobin, catalase, & cytochrome oxidase (15%)

Answer 1

Bilirubin

Question 2

Plasma concentration of bilirubin increases upon birth and reaches its peak on the ______

Answer 2

5th day

Question 3

If bilirubin synthesis > liver clearance rate:

Answer 3

↑bilirubin

Question 4

B1 / Indirect Bilirubin

Answer 4

• Unconjugated
• Water insoluble
• Non-polar B.
• Hemobilirubin
• Slow-reacting (needs accelerant to observe rxn)
• Prehepatic B.

Question 5

B2 / Direct Bilirubin

Answer 5

• Conjugated B.
• Water soluble
• Polar B.
• Cholebilirubin
• 1-min/Prompt B. (due to quick rxn to diazo rgt)
• Post-hepatic / Hepatic / Obstructive / Regurgitative B.
• Bilirubin diglucoronide

Question 6

o Abnormal form of bilirubin
o Conjugated bilirubin bounded to albumin so it has a longer half-life
o Forms due to prolonged elevation of conjugated bilirubin (B2).
o Helps in monitoring the decline of serum bilirubin following cholecystectomy
o Reacts w/ diazo reagent

Answer 6

Delta bilirubin

Question 7

Formulas:

Answer 7

Total Bilirubin = B1+ B2
Delta bilirubin = Total B. – (B1 + B2)

NOTE: Computation of delta B. cannot be performed if px is <14days old

Why? Bcos neonates normally have ↑bilirubin.

Question 8

characterized by yellow discoloration of the skin, sclera, and mucus membranes.

Answer 8

Hyperbilirubinemia

Question 9

↑B with yellow discoloration

Answer 9

Visible Jaundice

Question 10

↑B. but no visible yellow discoloration

Answer 10

Overt jaundice

Question 11

more commonly termed for serum or plasma w/ yellow discoloration due to hyperbilirubinemia

Answer 11

Icterus

Question 12

Sample spx for bilirubin

Answer 12

serum

Question 13

If Bilirubin sample is prepared & stored properly:

Answer 13

o Room temperature: 2 days
o Refrigerator (4°C): 1wk
o Freezer (-20°C): indefinite

Question 14

Bilirubin Interferences:

Answer 14

o Lipemia: false ↑bilirubin conc.
o Hemolysis: ↓rxn of bilirubin w/ diazo rgt (↓bilirubin)

Question 15

Bilirubin if exposed to light:

Answer 15

false ↓ by 30-50%/hr

Question 16

Principle:
▪ Van den Berg rxn: diazotization of bilirubin to form azobilirubin

Answer 16

Bilirubin Assay

Question 17

o Only measure B2 (also total bilirubin na rin).
o B1 is measured only by adding accelerants.
o Can measure B2 bcos it can directly react to diazo rgt.

Answer 17

Bilirubin Assay

Question 18

Bilirubin Assay 2 methods:

Answer 18

▪ Evelyn & Malloy
▪ Jendrassik & Groff

Question 19

Colorless end product of bilirubin metabolism that is oxidized by intestinal flora to urobilin or stercobilin

Answer 19

UROBILINOGEN

Question 20

Collection of sample for urobilinogen:

Answer 20

avoid light exposure

Question 21

Urobilinogen

Specimen:
Method:

Answer 21

Urobilinogen

• Specimen: 2-hr freshly collected urine or freshly collected stool.
• Method: Ehrlich’s method

Question 22

Why is Urobilinogen is ↓in biliary obstruction

Answer 22

bcos B2 cannot proceed to intestine for oxidation to UBG due to a blockage in biliary tract.

Question 23

• Test for hepatocellular fxn & check potency of bile duct.
• Rarely used bcos it involves administration of BSP dye.

Answer 23

BSP DYE EXCRETION

Question 24

Principle: Dye is injected & should then be excreted (since BSP has no physiologic fxn & only becomes a waste product once injected – waste should normally be excreted)

Answer 24

BSP DYE EXCRETION

Question 25

2 Methods of Administration for BSP DYE EXCRETION

Answer 25

o Rosenthal White method
o Mac Donald Method