Lab Medicine Flashcards
Liver Function tests
- Excretory
- Synthetic
- Integrity of hepatocytes
- Tests for cholestasis
Refer to Liver Case Scenario in Notes
..
Excterory Liver Function tests
- Serum bilirubin.
- Urinary Bile Pigment.
- Bile acids.
Synthetic Liver Function tests
- Plasma proteins.
- Prothrombin time.
Test for integrity of hepatocytes
- Transaminases (ALT & AST).
Tests for cholestasis
- Alkaline Phosphatase (ALP).
- Gamma Glutamyl Transferase (GGT).
Metabolism of Hb
How does Bilirubin exist in the serum?
- Unconjugated (indirect) bilirubin
- Conjugated (Direct) bilirubin
Compare between unConjugated & Conjugated bilirubin in terms of:
- Normal Site
- Solubility
- Fate
What is the Fate of urobilinogen?
- Most of it converted into stercobilin & excreted in feces (brown color).
- Part of it oxidized to urobilin & excreted in urine (yellow color).
Def of Delta-Bilirubin
- Conjugated bilirubin covalently bound to albumin.
Level of Delta-Bilirubin
- Normally: Absent or present in very small amount.
- Increases in: cholestasis (in parallel with other fractions).
Clearence of Delta-Bilirubin
- Cleared slowly from circulation to urine so:
- When jaundice resolves the delta fraction (which is not filtered) still present & bilirubin testing may become -ve in spite of high serum level.
Causes of increased unconjuguated bilirubin
Causes of increased Conjugated bilirubin
What is Gilberts Syndrome?
Most common cause of Unconjugated hyperblirubinemia
- Deficiency of uridinediphosphoglucuronyl transferase enzyme (UDP-GT).
- There is defect in the uptake by hepatocytes.
What is Dubin-Johnson Syndrome?
- A defect in excretion of bilirubin by hepatocyte.
Site of formation of plasma proteins
Most of them: in liver.
Except gamma globulins: in plasma cells.
Level of albumin
- Represent: 60% of total serum protein.
- Level: 3.5 - 5.0 g/di.
What happens to synthetic liver function tests in advanced hepatic affection?
What forms blood coagulation factors?
- Most of coagulation factors (except factor VIII) & fibrinolytic enzymes → by the liver.
- Factor VIII → by spleen.
What happens in patients with hepatocellular damage?
Concerning Blood coagulation factors
Decrease in Coagulation factors → Increase Prothrombin time [PT] (an early abnormality in this disease).
Normal site of ALT & AST
Inside Hepatocytes
What hapens to serum Levels of ALT & AST in hepatitis?
What is Preicteric phase?
- the period prior to appearance of jaundice
What happens to serum level of ALP in Obstructive Jaundice?
In obstructive jaundice “serum level is markedly elevated (>3 URL)”
What happens to serum level of GGT in cholestasis & Liver cirrhosis?
Serum Level: Inc. in cholestasis & liver cirrhosis (but the rise is marked in cholestasis).
What are other causes of elevated GGT?
Alcohol & barbiturates
Types of Plasma amaylase
- Salivary (S-isoenzyme)
- Pancreatic (P-isoenzyme): More specific & sensitive for diagnosis of acute pancreatitis.
- Total amylase activity > 10 times URL is virtually diagnostic of acute pancreatitis.