Hepatobiliary Testing

Question 1

AST (Aspartate Aminotransferase)

Answer 1

aka SGOT

Reference Range: 5 – 40 IU/L

AST is an intracellular enzyme; cellular damage causes enzyme to leak into plasma

Found in liver cells, cardiac muscle, skeletal muscle, renal cells, brain cells, pancreas, WBCs & RBCs

Question 2

AST Clinical use

Answer 2

Primarily for the evaluation of hepatocellular injury/necrosis

Previously used for detection of cardiac ischemia or myocardial infarction

Question 3

AST Increased levels implications

Answer 3

Liver disease
Heart disease
Skeletal muscle disease/injury

Acute hemolytic anemia
Acute pancreatitis
Acute cholangitis

Question 4

AST Decreased levels implications

Answer 4

Acute renal disease
Chronic renal dialysis

Question 5

ALT (Alanine Aminotransferase)

Answer 5

Reference Range: 5 – 53 IU/L

Intracellular enzyme that is more specific than AST for liver

Question 6

Clinical Uses for ALT

Answer 6

Diagnose and monitor hepatocellular injury or necrosis

Aid in diagnosis of jaundiced patient

Viral hepatitis
Alcoholic hepatitis

Question 7

Mild ALT increase implications

Answer 7

Myositis
Pancreatitis

Myocardial infarction
Infectious mononucleosis

Question 8

Moderate ALT increase implications

Answer 8

Moderate Increase

Cirrhosis
Cholestasis
Hepatic tumor

Obstructive jaundice
Severe burns
Muscle trauma

Question 9

Severe ALT increase implications

Answer 9

Severe Increase

Hepatitis, hepatic necrosis/ ischemia

Question 10

LDH (Lactic Dehydrogenase)

Answer 10

Reference Range: 90 – 190 IU/L

Intracellular enzyme in many body tissues

Total LDH elevation is relatively nonspecific; LDH isoenzymes offers more specificity

LDH 1 – myocardium, RBCs, brain, kidney
LDH 2 – myocardium, RBCs, brain, lung
LDH 3 – brain, kidney, lungs
LDH 4 – liver, skeletal muscle, brain, kidney
LDH 5 – liver, skeletal muscle, kidney

Question 11

Clinical Uses for LDH

Answer 11

Important diagnostic tool for hepatic dysfunction
Hemolysis and transfusion reactions

Specific injury patterns
LDH 1:2 “Flip” – cardiac necrosis

LDH 4 & 5 ⇑ - hepatitis, cirrhosis

LDH 5 ⇑ - hepatocellular disease/injury or skeletal muscle disease/injury

LDH 2, 3, 4, 5 ⇑ - lung and liver abnormality

All fractions ⇑ - multi-organ dysfunction or failure

Question 12

ALP (Alkaline Phosphatase)

Answer 12

Reference Range: 42 – 128 U/L

Enzyme originating mainly in the bone, liver and placenta

Question 13

Clinical use for ALP

Answer 13

Detection of bone diseases
Detection of liver diseases
Obstructive biliary diseases/conditions

Metastatic liver cancer
More specific ALP isoenzymes can help differentiate between liver & bone disease

Question 14

Implications of Increased levels of ALP

Answer 14

Cirrhosis
Biliary obstruction
Liver cancer

Normal pregnancy
Growing children
Bone mets

Intestinal ischemia
Hyperthyroidism
Hyperparathyroidism

Question 15

Implications of Decreased levels of ALP

Answer 15

Malnutrition
Hypothyroidism
Pernicious anemia

Magnesium deficiency
Celiac sprue

Question 16

GGT (Gamma-Glutamyltransferas)

Answer 16

Reference Range: <45 yrs = 5-27 U/L ; >45 yrs = 8-38 U/L

Highest concentrations in liver & biliary tract

Question 17

Clinical Uses of GGT

Answer 17

Sensitive indicator of hepatocellular disease or biliary obstruction

Elevations parallel ALP ⇑ but more sensitive
Indicate heavy & chronic alcohol use – elevations in chronic drinkers 75% of the time

Question 18

Implications of Increased levels of GGT

Answer 18

Liver disease
Pancreatic disease
Many cancers

ETOH
Phenytoin, barbituates
DM
Obestity

Question 19

Common patterns in liver disease

Answer 19

Question 20

Billirubin source and excretion

Answer 20

Breakdown of RBCs in RES releases Hgb + globin portion from the RBCs; heme is converted to biliverdin → bilirubin

Bilirubin initially is unconjugated (indirect)
Unconjugated bilirubin conjugates with glucuronide in the liver to form a conjugated (direct) form of bilirubin
Direct bilirubin is excreted from liver cells to hepatic ducts → common bile duct → bowel

Question 21

Bilirubin testing organization

Answer 21

Differentiation between direct & indirect to determine etiology of defect

Protect sample from light (>1 hr exposure can decrease bilirubin levels

Question 22

Clinical uses of bilirubin

Answer 22

Hepatocellular/Biliary tract disease/dysfunction
Evaluation of jaundice in adult patients

Evaluation of jaundice in newborns
Interference of testing methods with hemolysis and lipemic specimens

Question 23

Implications of increased indirect bilirubin

Answer 23

(pre-hepatic)

Erythroblastosis fetalis
Transfusion reaction
Sickle cell, pernicious, & hemolytic anemia

Large volume blood transfusion
Hepatitis, cirrhosis

Neonatal hyperbilirubinemia
Crigler-Najjar syndrome, Gilbert syndrome

Question 24

Implications of increased direct bilirubin

Answer 24

⇑ Levels of Direct (posthepatic)

Extrahepatic duct obstruction
Extensive metastatic liver cancer
Congenital defects in enzyme quantity

Question 25

Implications of increased levels of both indirect and direct bilirubin

Answer 25

⇑ Levels with both Direct & Indirect (hepatic)
Hepatocellular disease
Hepatotoxins
Hepatoma

Question 26

Markers of Hepatic Synthesis

Answer 26

The liver is largely responsible for coagulation factor and protein synthesis

Albumin – decreased levels indicate a chronic condition & are useful for monitoring progression of disease

Prothrombin time (PT) – in pts with chronic & severe hepatocellular injury, the PT is markedly prolonged (PTT is usually prolonged as well)

Question 27

Ammonia source hepatic implication

Answer 27

Ammonia is a breakdown product of protein catabolism which is converted to urea in liver & excreted by kidneys

In severe hepatocellular dysfunction it cannot be catabolized into urea

Question 28

Clinical uses of Ammonia

Answer 28

Specimen should be drawn in a green top tube and placed on ice immediately

Monitoring of severe liver disease and diagnosis or follow-up of hepatic encephalopathy

Question 29

Implications of increased Ammonia

Answer 29

*Hepatic encephalopathy
*Hepatocellular disease

Portal hypertension
GI bleeding

Obstruction with mild liver disease