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20 Cards in this Set
- Front
- Back
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List & describe some classical methods for measuring bilirubin.
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Methods for measuring bilirubin:
Vanden Bergh Ehrlich reaction Evelyn Malloy Jendrassik-Grof |
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Vanden Bergh bilirubin method:
Based on diazo reaction; bilirubin & diazotized sulfanilic acid solution--> direct measurement of the resulting colored azodipyrroles; alcohol accelerates the reaction of unconjugated bilirubin to determine total bilirubin; without alcohol = direct (conjugated) bilirubin |
Ehrlich reaction bilirubin method:
p-dimethylaminobenzaldehyde = Ehrlich's reagent |
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Evelyn Malloy bilirubin method:
Diazo reaction with methanol as an accelerator & the pH = 1.2; frequently used, but susceptible to significant Hgb interference. |
Jendrassik-Grof bilirubin method:
Diazo reaction if performed near neutral pH, but chromophore is measured at alkaline pH (apprx 13) at 600 nm. The accelerator is caffeine; most commonly used method; has higher molar absorptivity & thus is more sensitive & precise at low bilirubin concentration than Malloy-Evelyn method. |
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Describe the reaction for direct bilirubin.
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Direct bilirubin reaction:
Conjugated/direct bilirubin + diazotized sulfanilic acid--> azobilirubin (for beta, gamma & delta bilirubin) |
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When would you see a total bilirubin increased & a direct bilirubin decreased?
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TBI+ / DBI- :
Crigler-Najjar syndrome (impaired bilirubin conjugation in the liver); prehepatic jaundice as can be caused by prehepatic hemolysis. |
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Define indirect & direct bilirubin.
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DBI: conjugated bilirubin; noncovalently bonded (usually to glucuronic acid); water soluble: monoconjugated = beta; diconjugated = gamma; tightly bonded to albumin = delta.
Indirect bili: unconjugated bilirubin; water insoluble; alpha = loosely bond to albumin. |
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Why is bilirubin normally elevated in newborns?
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Bilirubin normally elevated in newborns:
(1) RBCs hemolyze (2) liver is just starting to function & needed enzymes for bilirubin metabolism & excretion are not there in sufficient concentrations. |
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Diagram bilirubin metabolism.
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Bilirubin metabolism:
RBC--> Hgb in macrophages in spleen or bone marrow--> Heme--> unconjugated bili--> conjugated bili (liver)--> gile (gall bladder)--> urobilinogen (intestine) that is excreted in feces or reabsorbed back into the blood & filtered by the kidneys into the urine. |
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Define kernicterus.
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Kernicterus: bilirubin accumulates in the CNS tissue; caused by hyperbilirubinemia; serious condition.
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How is physical jaundice managed in the newborn?
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Newborn jaundice.
Put newborn under a UV light because UV light destroys bilirubin. |
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Define the following diseases:
Gilbert's disease Dubin Johnson Physiological jaundice Crigler-Najjar disease |
Gilbert's disease:
Genetic; decrease in an enzyme activity (UDP-glucuronyltansferase) by 20-50%; bilirubin is conjugated at a decreased rate; results in a build-up of unconjugated/indirect bilirubin. |
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Physiological jaundice:
In newborns; temporary; an enzyme (gluconyl transferase) concentration is low & albumin levels for plasma transport of unconjugated bilirubin to liver are low; results in unconjugted hyperbilirubinemia. |
Dubin-Johnson disease:
Genetic; an obstructive liver disease in which excretion of conjugated bilirubin into the bile is impaired; results in an increase of conjugated/direct bilirubin. |
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Which of the following is/are associated with hyperbilirubinemia?
a. Crigler-Najjar disease b. Dubin-Johnson syndrome c. Muscular dystrophy d. Both a & b e. All of the above f. None of the above |
Hyperbilirubinemia seen in:
(d) both Crigler-Najjar disease and Dubin-Johnson disease |
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What is the reference range for an inant TBI & DBI?
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Ref range TBI/DBI (infants):
TBI: 8.0 mg/dL DBI: 0-0.3 mg/dL Normal in 10-15 days |
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Crigler-Najjar disease:Genetic; deletion of liver enzyme that metabolizes bilirubin; failure to break down bilirubin, which accumulates to toxic levels; patient becomes juandiced &must spend up to 16 hours a day under blue lights to break down pigment; fatal if untreated; liver transplant is only known cure.
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Bilirubin
Premature Full Term 24 hrs 1-6mg/dL 2-6 48 hrs 6-8 6-7 3-5 day 10-12 4-6 |
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State the advantages of teh Jendrassik-Grof method over the Evelyn-Malloy method.
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Jendrassik-Grof vs Evelyn-Malloy
E-M --> interference by Hgb J-G --> insensitive to sample pH changes; not affected by Hgb up to 7.5 g/dL; insensitive to 50-fold variation in protein concentration; adequate optical sensitivity even to decreased bilirubin concentrations. |
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What is the most common method currently used to analyze biilrubin in teh clinical lab?
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Most common bilirubin method:
Jendrassik-Grof |
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How is a specimen for bilirubin treated differently than a routine specimen & why?
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Bilirubin is very sensitive to & is destroyed by light & heat; therefore, specimens should be protected from ambient light prior to and during analysis.
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Contrast the results expected for conjugated bilirubin & conjugated bilirubin in prehepatic hepatic & posthepatic jaundice.
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Total bilirubin concentration: 5-15 mg/L
Conjugated bilirubin concentration: 0-2 mg/L Prehepatic: Conjugated: Decreased-Normal -- Unconjugated: Increased Hepatic: Conjugated: Decreased (or increased) -- Unconjugated: Normal Posthepatic: Conjugated: Increased -- Unconjugated: Normal |
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How is unconjugated bilirubin level calculated?
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Unconjugated bili calculation.
TBI-DBI (beta & gamma conj. & delta unconj) = Indirect/unconjugated |
