IRON AND BILIRUBIN Flashcards
Describe the methodology of the serum iron assay
- transferrin releases ferric iron in acidic conditions
- ferric iron is reduced to ferrous iron
- ferrous iron complexes with a chromogen = increased absorbance is measured
Ref: Iron
8-35 μmol/L
Ref: TIBC
40-75 μmol/L
Ref: Saturation Index
Female: 0.12 - 0.60
Male: 0.10 - 0.55
Ref: Ferritin
Female: 20 - 300 μg/L
Male: 30 - 500 μg/L
Ref: Transferrin
1.8 - 4.5 g/L
Ref: Total bilirubin
<20 μmol/L
Ref: Conjugated (direct) bilirubin
<7 μmol/L
Less than 0.1% of the body’s iron is present in plasma as __.
Less than 0.1% of the body’s iron is present in plasma as transferrin.
What is apotransferrin ?
- plasma protein
- transports ferric iron (Fe3+)
Plasma iron levels are highest in the __ and progressively __ over the day.
Plasma iron levels are highest in the MORNING and progressively DECLINE over the day.
What conditions are associated with increased serum iron ?
- hemochromatosis
- iron medication intake
- hormonal contraceptives
- aplastic anemia
What conditions are associated with decreased serum iron ?
- iron deficiency anemia
- hemorrhage
- menstruation
- medication
- anemia of chronic disease
How is TIBC measured ?
- Serum iron bound to transferrin is measured
- Excess ferric iron is added to saturate binding sites of transferrin; unbound excess iron is removed
- Serum iron assay is performed again and compared to the first measurement
How is excess iron removed during TIBC measurement ?
- Using either a silica or anion exchange column
OR
- Addition of magnesium carbonate
What causes increased TIBC ?
- iron deficiency anemia
- pregnancy
- oral contraceptives
What causes decreased TIBC ?
- chronic inflammatory disease
- malignancy
- hemochromatosis
Transferrin Saturation Calculation
Tsat% = [serum iron] / TIBC x 100%
What is ferritin ?
- the major storage form of iron
- acute phase reactant
- found in bone marrow, liver, spleen
What causes increased ferritin ?
- malignancies
- chronic infections
- hemochromatosis
- chronic inflammatory diseases (ie. SLE)
- hepatitis
The iron/ apotransferrin complex is also called __.
The iron/ apotransferrin complex is also called TRANSFERRIN.
Transferrin migrates to the __ region in SPE
Transferrin migrates to the β region in SPE
List 2 methods used to measure transferrin
- Immunoturbidimetry
- immunonephelometry
What causes increased transferrin ?
- pregnancy
- administration of estrogen
- iron deficiency
What causes decreased transferrin ?
- inflammation or malignancy (negative APR)
- decreased synthesis; chronic liver disease, malnutrition
- protein loss; nephrotic syndrome
What is FIT ?
Fecal Immunochemical Testing:
- detects hemoglobin in feces
- screening test for colorectal cancer
- 50 years+ should be tested every 2 years
What is bilirubin ?
- degradation product of heme
- transported in blood bound to albumin
- conjugated in liver and excreted into intestine with bile
- in the intestine, it is converted into urobilinogen
Describe the Diazo method for total Bilirubin + Interferences
- caffeine-benzoate-acetate is used to free unconjugated bilirubin from albumin (an accelerant)
Interferences:
- hemolysis, light exposure = false decrease
- lipemia = false increase
Describe the Direct Spectrophotometry method for Unconjugated Bilirubin + Interferences
- exclusively for neonates
Interferences:
- carotenoids absorb at 454nm; newborns do not have carotene
What is associated with neonatal jaundice ?
- immature liver cannot conjugate bilirubin and synthesize proteins
- intestinal flora is not developed = conjugated bilirubin cannot be reduced to urobilinogen for excretion
- hemoglobin F/ hemolytic disease of newborn = increased hemoglobin catabolism
- kernicterus = unconjugated bilirubin crosses blood-brain barrier
How can neonatal jaundice be treated ?
UV light therapy
Critical total bilirubin for children <30 days
> 300 µmol/L
Critical total bilirubin for children <30 days
> 300 µmol/L
Describe pre-hepatic bilirubin
INCREASED TOTAL bilirubin, INCREASED UNCONJUGATED bilirubin, normal conjugated bilirubin, negative urine bilirubin
- hemolytic anemia produces more bilirubin than the liver can process
Describe hepatic bilirubin
INCREASED TOTAL bilirubin, variable unconjugated bilirubin, variable conjugated bilirubin, variable urine bilirubin
- hepatocyte damage
- inherited disorders; inability to take up unconjugated bilirubin OR excrete conjugated bilirubina
Desribe post-hepatic bilirubin
INCREASED TOTAL bilirubin, normal unconjugated bilirubin, INCREASED CONJUGATED bilirubin, POSITIVE urine bilirubin
- CHOLESTASIS/ gallstones
- spasms or neoplasms prevent bilirubin from reaching intestine
Describe post-hepatic bilirubin
INCREASED TOTAL bilirubin, normal unconjugated bilirubin, INCREASED CONJUGATED bilirubin, POSITIVE urine bilirubin
- CHOLESTASIS/ gallstones
- spasms or neoplasms prevent bilirubin from reaching intestine
Differentiate Crigler-Naijar Syndrome Type I vs Type II
Inherited disorders of bilirubin metabolism
Type I:
- absence of UDP-glucoronyltransferase = HIGH UNCONJUGATED bilirubin
- kernicterus = severe brain damage/ death
- autosomal recessive
Type II:
- partial deficiency of UDP-glucoronyltransferase
- normal life expectancy w/ phenobarbital administration
- autosomal dominant
What is Dubin-Johnson/ Rotor Syndrome ?
- inherited disorder of bilirubin metabolism
- autosomal recessive
- HIGH CONJUGATED bilirubin with only slight increase in unconjugated bilirubin
- problem in excretion of conjugated bilirubin from hepatic microsome into canaliculi
What is Gilbert Syndrome ?
- inherited disorder of bilirubin metabolism
- autosomal recessive
- MILD increase in unconjugated bilirubin; no treatment needed
What is Lucey-Driscoll Syndrome ?
- inherited disorder of bilirubin metabolism
- inhibiton of bilirubin conjugation = HIGH UNCONJUGATED bilirubin
- occurs early neonatal period through 2-3 weeks post-delivery
TIBC Formula
TIBC = Serum iron + UIBC
