Chem unit 1

What is the reference range for AST?

5-35 u/L

What is the reference range for ALT?

7-45 u/L

What are the reference ranges for GGT for males and females?

males: 6-55 u/L

females: 5-38 u/L

What is the function of AST?

it is a transferase that is important in amino acid metabolism.

What is the function of ALT?

It transfers the amino group from alanine to alpha-ketoglutarate

How is ALT different than AST when it comes to determining laboratory results?

ALT is liver-specific, AST is not—it is found in the liver, heart, muscle, and kidneys.

What is the function of GGT?

It is a transferase in protein synthesis, glutathione regulation, and amino acid transport.

What does it mean when we see an increased GGT?

liver issue is alcohol-associated

What is the reference range for direct bilirubin in adults?

0-0.2 mg/dL

What is the reference range for indirect bilirubin in adults?

0.2-0.8 mg/dL

What is the reference range for total bilirubin in adults?

0.2-1.0 mg/dL

True or false: It is considered “normal” to have bilirubin in the urine.

False

What is the reference range for the total bilirubin in infants at 24 hours?

2-6 mg/dL

What is the reference range for the total bilirubin in infants at 48 hours?

6-7 mg/dL

What is the reference range for the total bilirubin in mature infants at 3-5 days?

4-6 mg/dL

What is the reference range for the total bilirubin in premature infants at 3-5 days?

10-12 mg/dL

What is the condition that severe unconjugated hyperbilirubinemia in infancy can result in?

kernicterus, which is permanent neurological damage

True or False: Total bilirubin will always be increased in those with jaundice.

True

Prehepatic jaundice is a problem of which organ(s), and what is the problem?

The problem is too much bilirubin production by the liver, spleen, and/or bone marrow. This causes an increase in unconjugated bilirubin.

Hepatic jaundice is a problem of which organ(s), and what are the 3 possible problems it can cause?

It is just a liver issue. It affects either:

1. hepatic uptake/conjugation, which causes an increase in unconjugated bilirubin.

2. bilirubin transport, which causes bilirubinuria and an increase in conjugated bilirubin.

3. or multiple functions, which can cause an increase in either conjugated or unconjugated bilirubin.

Posthepatic jaundice is a problem of which organ(s), and what is the problem?

It is caused by obstruction(s) in the bile duct or gallbladder, like inflammation, scar tissue, gallstones, or tumors. It causes bilirubinuria and an increase in conjugated bilirubin. A symptom of specifically posthepatic jaundice is a chalky, pale stool.

What is the most common cause of jaundice, and what is the significance?

Gilbert’s syndrome, it is genetic but typically does not cause any clinical consequences because conjugation still runs at 30% of normal. It causes intermittent unconjugated hyperbilirubinemia.

What percent of the population has Gilbert’s syndrome, and how is it passed genetically?

5% of the population

recessive mutation on chromosome 2 that codes for UGT1A1 enzyme

What is Crigler-Najjar syndrome, the two types, and what is its significance?

recessive mutation on chromosome 2 coding for UGT1A1 enzyme, but more severe (and rare) than Gilbert’s syndrome, can result in death

Type 1: complete absence of UGT1A1 enzyme

Type 2: severe deficiency of UGT1A1 enzyme

What is the cause of neonatal/physiologic jaundice?

immature UGT1A1 enzyme activity at birth, and is usually more pronounced in premature infants. Increased RBC turnover leads to increased bilirubin production.

How are results determined to call neonatal/physiologic jaundice, and what is a critical result?

Results are interpreted based on age in hours and gestational age. Severe and rapidly rising bilirubin is critical, because unbound bilirubin can enter the brain and cause kernicterus.

What are the two treatments for neonatal/physiologic jaundice?

1. Phototherapy, which converts unconjugated bilirubin into water-soluble photoisomers.

2. Blood exchange transfusion to remove hyperbilirubinemic blood and replace it with new blood.

What is Dubin-Johnson syndrome, and how is it passed genetically?

It is a recessive gene causing MRP2 protein deficiency, making excretion into bile defective. It causes bilirubinuria and an increase in conjugated bilirubin. No treatment is required. It’s hallmark is a black liver.

What is Rotor syndrome, and how is it caused genetically?

It is caused by mutations affecting OATP1B1 and OATP1B3, which impairs reuptake of conjugated bilirubin so it remains in circulation. It causes mild increased conjugated bilirubin and bilirubinuria. No treatment is needed.

What will bilirubin and related results look like in a person with posthepatic jaundice?

Increased conjugated bilirubin, possibly increased unconjugated bilirubin, bilirubinuria present.

What will bilirubin and related results look like in a person with prehepatic jaundice?

Increased unconjugated bilirubin, urobilinogenuria present.