To see a Yellow Fellow
This bilirubin fraction is typically absent from urine, even when markedly elevated in serum.
Unconjugated bilirubin
A serum specimen for bilirubin testing is left exposed to sunlight for several hours. What effect will this have on the reported bilirubin concentration?
Falsely decreased
A patient with prolonged biliary obstruction develops an elevated PT/INR due to malabsorption of which vitamin?
Vitamin K
A jaundiced patient has elevated indirect bilirubin, increased LDH, low haptoglobin, and reticulocytosis. What is the most likely cause?
Hemolysis (prehepatic jaundice)
A jaundiced patient has ALT 850 U/L, ALP 120 U/L, and total bilirubin 5.2 mg/dL. What pattern of liver injury is most likely?
Hepatocellular injury
During erythrocyte breakdown, which enzyme converts heme into biliverdin, releasing iron and carbon monoxide?
Heme oxygenase
A patient with complete biliary obstruction develops pale, clay-colored stools. Which bilirubin-derived pigment is no longer being produced in sufficient amounts to give stool its normal brown color?
Stercobilin
A patient with acute liver injury develops a prolonged PT/INR while albumin remains normal. Which coagulation factor's short half-life helps explain this early change?
Factor VII
A jaundiced patient has the following results:
Total bilirubin: 8.0 mg/dL
Direct bilirubin: 6.5 mg/dL
Urine bilirubin: Positive
Urine urobilinogen: Undetectable
What type of jaundice is most likely?
Obstructive (posthepatic) jaundice
In the diazo method, conjugated bilirubin reacts directly with the reagent, but unconjugated bilirubin requires an additional substance to react. What is this substance called?
An accelerator
A patient has an ALP of 510 U/L. Which additional enzyme helps distinguish a hepatobiliary source from a bone source?
GGT
In the Jendrassik–Grof bilirubin assay, which reagent terminates the diazo reaction by destroying excess diazo reagent?
Ascorbic acid
(Vitamin C)
A patient's AST is 310 U/L, but ALT is 42 U/L and ALP is 95 U/L. The specimen has a markedly elevated hemolysis index. What preanalytical interference could explain the AST elevation?
In vitro hemolysis
After biliary obstruction resolves, a patient's direct bilirubin remains elevated for weeks despite improving liver enzymes. Which bilirubin fraction explains this finding?
Delta bilirubin
A patient with biliary obstruction has ALP of 850 U/L. Unlike AST and ALT, this marked elevation is primarily caused by increased enzyme production. What triggers this increase?
Accumulation of bile acids in hepatocytes
A patient with alcohol-associated liver disease has AST 210 U/L and ALT 80 U/L. Deficiency of which vitamin-derived cofactor contributes to the disproportionately low ALT activity?
Pyridoxal phosphate
(Vitamin B6)
A 22-year-old develops intermittent jaundice during illness.
Total bilirubin: 3.5 mg/dL
Direct bilirubin: 0.2 mg/dL
AST, ALT, and ALP: Normal
LDH, haptoglobin, and reticulocytes: Normal
Which hepatic enzyme has reduced activity in this patient?
UGT1A1
(UDP-glucuronosyltransferase)
A patient has the following laboratory findings:
Predominantly conjugated hyperbilirubinemia
Normal AST, ALT, ALP, and GGT
Urinary coproporphyrin isomer I exceeds 80%
Which inherited disorder is most likely?
Dubin–Johnson syndrome
A patient with obstructive jaundice has elevated ALP, GGT, and INR. Twenty-four hours after adequate parenteral vitamin K administration, the INR remains elevated. Anticoagulant use and other causes of coagulopathy have been excluded. What hepatic dysfunction does this suggest?
Impaired hepatic synthetic function
A patient has conjugated hyperbilirubinemia, positive urine bilirubin, and normal liver enzymes. Unlike Dubin–Johnson syndrome, the defect involves impaired hepatic uptake and reuptake. What disorder is this?
Rotor syndrome