360 - Iron & Bilirubin

Question 1

The majority of the body’s iron, approximately 94% is distributed in…

Answer 1

hemoglobin, ferritin, and hemosiderin

Question 2

Less than 0.1% of the body’s iron is present in plasma as…

Answer 2

transferrin

Question 3

a plasma protein that transports ferric iron (Fe3+) from one organ to another

Answer 3

apotransferrin

Question 4

Normally, approximately ___ of the iron binding sites of transferrin are occupied by iron

Answer 4

1/3

Question 5

Plasma iron levels are highest in the ___________ and progressively ______ over the day

Answer 5

morning; decline

Question 6

causes of increased serum iron

Answer 6

hemochromatosis

iron meds

hormonal contraceptives

aplastic anemia

Question 7

causes of decreased serum iron

Answer 7

IDA

hemorrhage

menstruation

medication

anemia of chronic disease

Question 8

TIBC

Answer 8

total iron binding capacity

1. serum iron is measured as described
2. ferric iron (Fe3+) is added in excess to the sample to saturate the binding sites on transferrin

excess iron is removed by either a silica or anion exchange column, or by the addition of magnesium carbonate; serum iron assay performed after to compare to first measurement

Question 9

increased TIBC

Answer 9

IDA

pregnancy

oral contraceptives

Question 10

decreased TIBC

Answer 10

chronic inflammatory disease

malignanacy

hemochromatosis

Question 11

major storage form of iron

Answer 11

ferritin
- acute phase protein
- found in BM, liver, spleen
- detected by immunoassay

Question 12

increased ferritin

Answer 12

malignancies

chronic infections

hemochromatosis

chronic inflammatory diseases (SLE)

hepatitis (eg. viral)

Question 13

decreased ferritin

Answer 13

IDA

Question 14

where is apotransferrin produced?

Answer 14

produced by the liver and carries ferric iron in the blood; the iron/apotransferrin complex is known as transferrin

Question 15

how can we measure apotransferrin?

Answer 15

immunoturbidimetry

immunonephelometry

Question 16

increased transferrin

Answer 16

pregnancy

administration of estrogen

iron deficiency

Question 17

decreased transferrin

Answer 17

negative AP: rxn to inflammation, malignancy

decreased synthesis: chronic liver disease, malnutrition

protein loss: nephrotic syndrome

Question 18

fecal immunochemical testing (FIT)

Answer 18

detects hemoglobin in feces
screening test for colorectal cancer
recommended for 50y/o; test every 2 years

Question 19

FIT test reaction

Answer 19

monoclonal or polyclonal Ab + Hb => Ab-Ag product

Question 20

a degradation production of heme

Answer 20

bilirubin

Question 21

main sources of heme

Answer 21

aged red blood cells, myoglobin, cytochromes, and peroxidases

Question 22

how is bilirubin transported in blood

Answer 22

bound to albumin

Question 23

what happens to bilirubin in the liver?

Answer 23

it is conjugated to produce bilirubin monoglucuronide and diglucuronide

both products excreted into intestine with bile

intestine = bilirubin monoglucuronide is hydrolyzed and reduced to form urobilinogen => may further degraded to urobilin

Question 24

method for measuring total bilirubin

Answer 24

diazo method (modified Jendraski-Grof method)

Bilirubin + Diazotized sulfanilic acid -> azobilirubin

Question 25

this is used as an accelerant in diazo method as it frees unconjugated bilirubin from albumin

Answer 25

caffeine-benzoate-acetate

Question 26

which wavelength is used to measure bilirubin?

Answer 26

530 nm

Question 27

interefernece in measuring bilirubin

Answer 27

- lipemia = false INCREASE - hemolysis = false DECREASE - exposure to light = false DECREASE

Question 28

Direct spectrophotometry for Unconjugated Bilirubin

Answer 28

- exclusively used for newborn children - [bilirubin] directly determined at 454 nm - bichromatic measurement is used to eliminate interference from oxyhemoglobin > absorbance at 454 nm minus the absorbance at 540 nm equals the true bilirubin absorbance

Question 29

interference of direct spectrophotometry for unconjugated bilirubin

Answer 29

carotenoids absorb at 454 nm, but newborn children do not have carotene

Question 30

neonatal jaundice

Answer 30

- immature livers cannot conjugate bilirubin = cannot synthesize proteins - HbF = increased catabolism of Hb - neonates, intestinal flora not fully developed = conjugated bili does not get reduced to urobilinogen for excretion - hemolytic disease of newborns = increased Hb catabolism - may be treated with UV light therappy

Question 31

Critical levels of unconjugated bilirubin may cause THIS which can result in brain damage (neonatal jaundice)

Answer 31

KERNICTERUS

Question 32

critical balue of total bilirubin in children <30 days old

Answer 32

>300 umol/L

Question 33

pre-hepatic jaundice

Answer 33

Hemolytic anemia may produce more bilirubin than the liver can process

Question 34

hepatic jaundice

Answer 34

Damage to the hepatocytes, or inherited disorders result in the inability to conjugate or excrete conjugated bilirubin, or inability to take up unconjugated bilirubin for conjugation and excretion

Question 35

post-hepatic jaundice

Answer 35

cholestasis - gallstones, spasms, or neoplasms may prevent bilirubin-glucuronide from reaching the intestine

Question 36

inherited disorders of bilirubin metabolism (hepatic jaundice)

Answer 36

Crigler-Najjar Syndrome Type I " Type II Dubin-Johnson Syndrome Rotor Syndrome Gilbert Syndrome Lucey-Driscoll Syndrome

Question 37

Crigler-Najjar Syndrome Type I

Answer 37

complete absence of UDP-glucuronyltransferase, resulting in very high concentrations of unconjugated bilirubin autosomal recessive Kernicterus results in severe brain damage and usually results in death

Question 38

Crigler-Najjar Syndrome Type II

Answer 38

autosomal dominant disorder is the result of a partial deficiency in UDP-glucuronyltransferase. Normal life is expected with phenobarbital administration

Question 39

Dubin-Johnson Syndrome

Answer 39

- autosomal recessive condition with jaundice - elevated levels of conjugated bilirubin with only a slight increase in unconjugated bilirubin - problem involves the excretion of conjugated bilirubin from the hepatic microsomes into the canaliculi

Question 40

Rotor Syndrome

Answer 40

similar to Dubin-Johnson Syndrome.

Question 41

Gilbert Syndrome

Answer 41

probably autosomal recessive with mild unconjugated hyperbilirubinemia. No treatment is required

Question 42

Lucey-Driscoll Syndrome

Answer 42

- caused by an inhibitor of bilirubin conjugation - unconjugated bilirubin levels are increased - occurs in the early neonatal period lasting about 2 -3 weeks post-delivery