Liver function tests can evaluate for liver injury and dysfunction. Elevated levels of aminotransferases AST and ALT indicate hepatocyte injury, while elevated alkaline phosphatase and bilirubin suggest cholestasis or bile flow obstruction. Tests of synthetic function include albumin and coagulation factors. Specific diseases are identified by viral hepatitis serologies, iron studies, ceruloplasmin, and antimitochondrial antibodies. Abnormal tests must be interpreted in context of the clinical picture and potential non-hepatic causes. Liver biopsy may be needed to determine etiology and severity of injury when tests are inconclusive.

1. Evaluation of Liver Injury
Mark J. Czaja
Liver Research Center
Albert Einstein College of Medicine
Bronx, N.Y.

2. Liver Function Tests
• Alanine aminotransferase (ALT)
• Aspartate aminotransferase (AST)
• Lactate dehydrogenase (LDH)
• Alkaline phosphatase
• Bilirubin
• Albumin

3. Mechanisms of Liver Dysfunction
• Direct cellular injury
• Blockage in bile flow
• Impaired blood flow

4. Direct Cellular Injury - HCV Infection

5. Blockage in Bile Flow - Biliary
Atresia

6. Impaired Blood Flow - CHF

7. Consequences of Liver Injury
liver cell injury
liver cell death
proliferation matrix deposition
sufficient inadequate altered architecture
recovery liver failure cirrhosis

8. Types of Liver Tests
• True tests of liver function
• Biochemical markers of liver injury
• Biochemical markers of specific
liver diseases

9. Testable Biochemical Liver
Function
• Ability to transport organic anions
• Capacity to metabolize certain
substances
• Capability to synthesize various
proteins

10. Steps in Organic Anion Transport
• Delivery and uptake
• Metabolic alteration
• Secretion and excretion

11. Bilirubin
• Tetrapyrole
• Toxic in neonates - kernicterus
• Derived from:
 Senescent RBC (70-80%)
 Hemoproteins (20-30%)
 Ineffective erythropoiesis

12. Bilirubin Formation
heme biliverdin bilirubin
heme
oxygenase
biliverdin
reductase
Transport: hydrophobic due to internal H-bonding
circulates bound to albumin

13. Bilirubin Metabolism
UCB
ligandin
glucuronyl
transferase
BMG
BDG
Alb
UCB
BMG
BDG
Plasma Hepatocyte Bile
BMG
BDG

14. Bilirubin Elimination
Intestine
• BMG (20%) +
BDG (80%)
+UCB (trace)
• Deconjugated to
urobilinogen
• Excreted or reab-
sorbed (20%)
Urine
• BMG and BDG
• No UCB

15. Measurement of Serum
Bilirubin
• Normal concentration < 1 mg/dl
• Conjugated < 5%
• Jaundice if > 3 mg/dl
• Detected by diazo reaction - cleaved
to colored azo-dipyrole
 Conjugated reacts rapidly (direct)
 Unconjugated reacts slowly (indirect)

16. Differential Diagnosis I
• Prehepatic
• Intrahepatic
 Congenital
 Acquired
• Posthepatic

17. Differential Diagnosis II
• Unconjugated hyperbilirubinemia
 Increased bilirubin production
(hematological)
 Decreased uptake (drug)
 Decreased conjugation (congenital)
• Conjugated hyperbilirubinemia
 Congenital
 Drug
 Liver disease
 Biliary obstruction

18. Inherited Disorders Causing
Unconjugated Hyperbilirubinemia
• Crigler-Najjar syndrome
 Type 1 – absent GT
 Type 2 – reduced GT activity
• Gilbert’s syndrome – reduced GT
activity due to genetic defect in
TATAA element of GT promoter

19. Inherited Disorders Causing
Conjugated Hyperbilirubinemia
• Dubin-Johnson syndrome –
mutations in multidrug resistance
associated protein 2 (MRP2)
• Rotor’s syndrome – genetic
defect

20. Hepatic Metabolic Capacity
• Clearance must depend on total
functional mass or metabolic activity
• Hepatic drug metabolism -
[14C]amino-pyrine breath test
• Galactose elimination
• Not used clinically

21. Hepatic Synthetic Capacity
• Most major plasma proteins are made
in the liver
• Decreased hepatocytes = decreased
protein synthesis and release
• Albumin and coagulation factors are
clinically important

22. Albumin
• 50% of all synthesized hepatic
protein
• Determinant of plasma oncotic
pressure
• Important transport protein

23. Serum Albumin Levels
• Long half-life of 20 days
• Large hepatic synthetic reserve
• Decreased with persistent, large injury
• Decreased in chronic liver disease
• Poor prognostic sign

24. Non-hepatic Causes of
Hypoalbuminemia
• Severe malnutrition
• Renal or GI loss
 Glomerulopathy, HIV enteropathy
• High catabolism
 Infections, burns

25. Coagulation Factors
• Half-lives of hours to days
• Liver synthesizes I, II, V, VII,
IX, and X
• Large synthetic reserve

26. Prothrombin Time (PT)
• PT detects abnormalities in I, II,
V, VII and X (extrinsic pathway)
• PT is increased in liver disease
• Best prognostic indicator
 Acute liver disease
 Chronic liver disease

27. Non-hepatic Causes of
Elevated PT
• Congenital coagulation factor
deficiencies
• Consumptive coagulopathies
• Vitamin K deficiency (II, VII, IX, X)

28. To Rule Out Vitamin K Deficiency
• Any patient with an elevated PT
• Parental vitamin K for 3 days
• Normalization of PT - vitamin K
deficiency
• Failure to normalize - hepatocellular
disease

29. Serum Immunoglobulins
• Not produced by hepatocytes
• Frequently elevated in liver disease
• Secondary to inflammatory process
• ? produced by antigen shunting

30. Biochemical
Markers of Liver
Injury

31. Liver Enzymes
• Low levels always present in serum
• Leak out from cell after injury
• Very sensitive
• Magnitude of abnormality does not
correlate well with degree of injury

32. Aspartate Aminotransferase
(AST)
• Serum glutamic-oxaloacetic
transaminase (SGOT)
• Transfers an a-amino group of aspartate
to a-keto group of ketoglutaric acid
• Present in skeletal muscle, kidney, brain

33. Alanine Aminotransferase
(ALT)
• Serum glutamic-pyruvic transaminase
(SGPT)
• Transfers an a-amino group of alanine
to a-keto group of ketoglutaric acid
• Present principally in liver

34. AST and ALT
• Elevated in most liver diseases
• Highest levels are in acute liver
diseases
• Only slight elevations in chronic
liver diseases
• Usually increase in parallel

35. AST/ALT in Alcoholic
Hepatitis
• Transaminases rarely exceed 300
• AST:ALT >2

36. Factors Affecting AST/ALT
• Depressed by pyridoxine (vit. B6)
deficiency
• Decreased by uremia and renal dialysis

37. AST/ALT Controversies
• Should lower normal limits be
used in females?
 Females < 30 vs. males < 40
• Are the normal limits too high?
 Females < 20 and males < 30

38. Lactate Dehydrogenase
(LDH)
• Component of classic LFT’s
• Highly non-specific

39. Tests of Impaired Hepatic
Excretion
Increased In
• Cholestasis
• Intra-hepatic biliary tract obstruction
• Extra-hepatic biliary obstruction

40. Alkaline Phosphatase
• Hydrolyzes phosphate esters at
alkaline pH
• Also present in bone, kidney, placenta,
intestine
• Mainly liver and bone in adults
• Increased in children from bone growth
• Placental form during pregnancy

41. Elevated Alkaline Phosphatase
• Can occur in any liver disease
• Highest with cholestasis or biliary tract
obstruction
• Elevated in infiltrative diseases
• Due to increase synthesis and secretion

42. Alkaline Phosphatase Isoenzymes
Source
Heat
Inactivation 5' NT GGTP
Liver Moderate + +
Bone Rapid - -
Placenta Slow - -
Intestine Slow - -

43. 5'-Nucleotidase
• Hydrolyzes 5'- adenosine monophosphate
• Mainly present in liver
• Increases along with alkaline phosphatase

44. g-Glutamyl Transpeptidase
(GGTP)
• Transfers g-glutamyl groups
• Widely distributed
• Sensitive correlate to alkaline phosphatase
• Non-specific (alcoholism, MI, DM,
pancreatic disease, renal failure)

45. Biochemical Markers
of Specific Liver
Diseases

46. Etiology-specific Liver Tests
• Viral hepatitis serologies
• Serum ferritin level
• Ceruloplasmin level
• Alpha1-antitrypsin level
• Antimitochondrial antibody titer

47. Viral Hepatitis Serology
• HAV – anti-HAV IgM and IgG
• HBV – HBsAg, anti-HBsAg,
and anti-HBcAg
• HCV – anti-HCV, HCV RNA

48. Serum Ferritin
• Widely distributed storage protein
• Levels reflect body iron stores
• Elevated in primary hemochromatosis
• Elevated in acute inflammation and
cirrhosis

49. Serum Ceruloplasmin
• Copper-binding protein
• Decreased in 95% of patients
with Wilson’s disease
• 20% of heterozygotes have
decreased levels

50. a1-Antitrypsin
• Inhibits serum trypsin
• Major component of a1-globulin
• Deficiency cause of neonatal
hepatitis

51. Antimitochondrial Antibody
(AMA)
• Directed against mitochondrial
enzyme pyruvate
dehydrogenase complex
• Positive in 90% of patients
with primary biliary cirrhosis

52. Interpretation of Abnormal
LFT’s
• Examine multiple tests
• Consider non-hepatic causes
• Determine the most abnormal tests

53. Hepatocellular vs. Cholestatic
Test Hepatocellular Cholestatic
ALT/AST 2-3 NL-1
Alk Phos NL-1 2-3
Bilirubin NL-3 NL-3
Albumin NL-3 NL
PT NL-3 NL

54. Case 1
• ALT 2045 (15-45)
• AST 2300 (15-45)
• Alk Phos 273
(50-150)
• Bili 3.9 (0.1-1.0)
• Alb 4.2 (3.5-5.5)
• PT 11.5 (10-12)
25 yo IVDA c/o 1 week of nausea,
vomiting, and myalgias. Physical
exam revealed jaundice.

55. Hepatocellular W/U
H & P
EtOH, medications, transfusions
Risk for viral
hepatitis
Risk factors
for NASH
Autoimmune
features
Etiology-specific LFT’s
USG and liver biopsy

56. HBV Infection - HBcAg Staining

57. Case 2
• ALT 75 (15-45)
• AST 115 (15-45)
• Alk Phos 650
(50-150)
• Bili 10.2 (0.1-1.0)
• Alb 4.2 (3.5-5.5)
• PT 11.0 (10-12)
67 yo c/o several months of weight loss,
and 1 week of nausea, vomiting, and
myalgias. Physical exam revealed
cachexia and jaundice.

58. Cholestatic W/U
H & P
medications, gallstones, weight loss
AMA
USG
ERCP
liver biopsy
dilated ducts
normal

59. Pancreatic Carcinoma - ERCP