A detailed approach to Liver function tests including clinical scenerios and algorithms

1. Liver function tests
Dr Abhra Ghosh

2. FUNCTIONS OF LIVER
1. Metabolic functions:
- Formation of Urea
- Synthesis of Cholesterol
- Interconversion of carbohydrates
- Catabolism of nucleic acids
2. Secretory functions:
- Bile formation and secretion
3. Excretory functions:
- Excretion of exogenous dye
4. Synthesis of coagulation factors
- Factor II, V, VII, X
- Fibrinogen
5. Synthesis of other proteins
- Albumin
- Alpha and beta globulins
6. Detoxification
7. Storage function
- Glycogen, Vit B12, Vit A etc

3. When do we go for LFT?
1. Fatigue, weight loss, flatulent dyspepsia, anorexia and low-grade fever
2. Haematemesis, melaena, swelling of legs and progressive distension of abdomen
3. Jaundice
4. Features of hepatocellular failure
5. Features of portal hypertension

4. Classifiction of LFT
1. Tests based on abnormalities of bile pigment metabolism:
- Serum bilirubin and VD Bergh reaction
- Urine bilirubin
- Urine and fecal urobilinogen
2. Serum enzyme activity in liver diseases

5. Jaundice and its clasification
Jaundice is –
Yellowish discolouration of skin and mucosa due to increased bilirubin level
• Noraml - <0.8 mg/dL
• Subclinical jaundice – 0.8 to 2.0 mg/dL
• Clinical jaundice - >2.0 mg/dL
Why bilirubin gets deposited in skin and mucosa?
Why there is itching in a case of jaundice?

6. Clasification of jaundice
1. By Rolleston and McNee:
a. Hemolytic or pre-hepatic jaundice
i) Intrinsic
ii) Extrinsic
b. Hepatocellular or hepatic jaundice
i) Defective conjugation
ii) Viral or toxic jaundice
iii) Cholestatic jaundice
c. Obstructive or post-hepatic jaundice
2. Rich’s classification
i) Retention jaundice
ii) Regurgitation jaundice

7. Interpretation - Van Den Bergh reaction
• Bilirubin formed and not passed though liver – Uncon. Bili. – Indirect reaction
• Bilirubin formed and passed through liver – Con. Bili. – Direct reaction
Hemolytic Jaundice - ↑ Unconjugated bilirubin - Indirect reaction
Obstructive jaundice - ↑ Conjugated bilirubin – Direct reaction
Hepatocellular jaundice - ↑ Conju./Unconjugated bilirubin - Biphasic
VD Bergh reaction does not differentiate b/w intrahepatic or post hepatic jaundice

8. Causes of hemolytic jaundice
1. Intraerythrocytic defects
a. Hereditary – Spherocytosis, sickle cell disease, thalassaemia, G6PD deficiency
b. Acquired – B12 and folate deficiency
2. Extraerythrocytic defects
a. Autoimmune hemolytic anemia
b. Malaria
c. Prosthetic heart valves
d. Drugs like sulphalazine and dapsone
e. Paroxysmal nocturnal hemoglobinuria

9. Causes of hepatocellular jaundice
1. Viral hepatitis
2. Alcoholic hepatitis
3. Chronic hepatitis
4. Cirrhosis
5. Drug induce hepatitis
- Chlorpromazine, imipramine
- INH, rifampicin, erythromycin
- Amitryptyline, halothane, methyldopa

10. Causes of Obstructive jaundice
1. Small duct obstruction
- Drugs, alcohol
- Viral hepatitis, cirrhosis
- Chronic cirrhosis
- Primary biliary cirrhosis
- Hodgkin’s disease
- Metastasis
- Ulcerative cholitis
2. Large duct obstruction
- Gall stone in CBD
- Ca Head of pancreas
- Ca ampulla of vater
- Stricture of bile ducts
- Sclerosing cholangitis
- Helminths in CBD
- Carcinoma in bile ducts
3. Inborn errors of bile
secretion
- Progressive familial
intrahepatic
cholestasis
- Benign recurrent
intrahepatic
cholestasis

11. Hemolytic
jaundice
Hepatocellular
jaundice
Obstructive
jaundice
Total bilirubin Elevated Elevated Elevated
Conjugated
bilirubin
Normal Elevated Elevated
Unconjugated bil Elevated Elevated Normal
Van den Bergh
recation
Indirect Biphasic Direct

12. Algorithm for diagnosing familial causes of hyperbilirubinemia
Isolated ↑ serum bilirubin
Ruling out of hemolysis, subsequent fractionation of the bilirubin
Possibility of the following –
• Dubin Johnson
• Rotor
Possibility of the following
• Gilbert <3mg/dL
• Crigler-Najjar – 1, >25 mg/dL
• Crigler – Najar – 2, 5 – 20 mg/dL
• Lucey-driscoll, ~ 5mg/dL
Conjugated Unconjugated

13. Bile pigments in urine
• Conjugated bilirubin can pass through the glomerular filter Present in urine in
cholestatic jaundice
• Unconjugated bil. is attached to albumin  cannot cross the glomerular
membrane
• Bilirubinuria is always accompanied with direct VD Bergh reaction

14. Bile pigments in faeces
• Normally absent
• May present in case of rapid passage of intestinal contents
• Neonates – due to absence of gut flora  Meconium is of green clour
• Patients taking gut sterilizing antibiotics

15. Faecal urobilinogen
• 50 – 250 mg of urobilinogen excreted per day
• ↑ in hemolytic jaundice – dark coloured stool
• Absent/decreased in obstructive jaundice – clay coloured stool
• Complete absence of faecal urobilinogen  Malignant obstruction

16. Urine urobilinogen
• Mere traces – maximum 4 mg/day
• Absence – Obstructve jaundice
- So, Bilirubin (+) , Urobilinogen (-)  Obstructive jaundice
(Fouchet’s test +ve)
• ↑ Urobilinogen  hemolytic jaundice
- So, Bilirubin (-) , Urobilinogen (+)  Hemolytic jaundice
(Ehrlich’s test +ve)
• ↑ Urobilinogen  damage to the hepatic parenchyma
- So, Bilirubin (+) , Urobilinogen (+)  Hepatic jaundice (Hay’s test
+ve)

17. Serum enzymes in Liver diseases
1. Most commonly done -
- Serum transaminases
- Serum alkaline phosphatases
2. Not routinely done -
- Serum 5’ nucleotidase
- Serum lactate dehydrogenase
- Serum isocitrate dehydrogenase
- Serum cholinesterase
- Serum ornithine carbamoyl transferase
- Serum leucine amino peptidase
- Serum 𝛄-Glutamyl transferase

18. Serum transaminases
• Markers for liver parenchymal injury
• Differential distribution causes overlapping of serum values
• Heart muscles are richer in AST
• Liver contains both - more of ALT
• Helps in assessing severity and prognosis of parenchymal disease – acute
hepatitis
• Normal value – ALT - <45 U/L (M), <34 U/L (F)
AST - <35 U/L (M), <31 U/L (F)

19. Serum transaminases
• Both AST and ALT have two isoenzymes
• Activity of ALT in hepatocytes is higher than AST
• Cell injury causes release of enzyme into plasma
• Normal AST/ALT ratio (in plasma) – 0.8
• Higher ratio seen in (>2) –
- Alcoholic hepatitis, Cirrhosis, NASH, Liver mets,
• Lower ratio seen in (<0.8) –
- Acute hepatocellular injury, toxic exposure, cholestasis
Mitochondrial
Cytosolic

20. Serum Alkaline phosphatase
• 5 isoenzymes - Hepatic – two types, Bone, Placental, Intestinal
• In liver, it is a membrane bound glycoprotein
• Level increases by - ↑ synthesis, membrane fragmentation by bile acids,
solubilization of membrane bound enzymes
• High values in – obstructive jaundice (>270 U/L)
• Other causes – Abscess, primary carcinoma (hepatoma), metastatic
carcinoma, infiltrate lesions like lymphoma, granuloma
• Hepatic type – 2 type – Major (α2 band), fast (α1 band)
• Major type - from regurgitation of bile, fast type – intrahepatic obstruction

21. Serum Alkaline phosphatase
Normal levels –
• Male (4 - 15 y) – 54 – 369 U/L
• Female (4 – 15 y) – 54 – 369 U/L
• Male (20 – 50 y) – 53 – 128 U/L
• Female (20 – 50 y) – 42 – 98 U/L
• Male (>60 y) – 56 – 119 U/L
• Female (>60 y) – 53 – 141 U/L

22. Serum 5’ - Nucleotidase
• Hydrolysis nucleotides on carbon atom 5’ of ribose
• Breaks into adenosine and inorganic phosphate
• It is a membrane bound glycoprotein
• Increases in biliary diseases, but not in bone diseases
• Combined use of ALP and Serum 5’ – Nucleotidase is diagnostic of biliary
obstruction
• Normal level – 2 – 17 IU/L

23. Serum Lactate dehydrogenase
• Widely distributed in tissue
• Less specific
• Increase in infectious hepatitis,
• Also increase in non-liver disease – leukaemia, pernicious anemia,
megaloblastic anaemia
• Remain normal – Cirrhosis, post hepatic jaundice
• Normal level – 70 – 240 IU/L

24. Serum 𝛄-Glutamyl transferase
• Enzyme for detection of alcohol abuse
• Alcohol causes microsomal stimulation
• Not specific
• ↑ by hepatocellular disruption and induction by drugs
• Normal – 10 – 47 IU/L
Two main use –
• ↑ 𝛄-Glutamyl transferase and ↑ ALP  Hepatic origin
• Sudden ↑ in 𝛄-Glutamyl transferase  Recent bout of intake of alcohol

25. Hepatospecific enzymes
❖ Serum Ornithine carbamoyl transferase
• Enzyme for urea synthesis, Normal level – 8 – 20 mIU/L
• ↑ hepatocellular/biliary tract injury only – acute viral hepatitis, cholestasis,
cirrhosis, mets
❖ Serum sorbitol dehydrogenase
• Converts sorbitol to fructose, normal level - <0.2 mIU/L
• ↑ acute viral hepatitis, toxic hepatitis, no extrahepaptic source except kidney
and prostate (controversial)
• Prognostic value

26. Abnormal Liver-associated enzymes
AST/ALT > ALP ALP > AST/ALT
Hepatocellular disease Cholestatic disease
Chronic
hepatitis
Evidences of
cirrhosis
Acute hepatitis
Extrahepatic
obstruction
Intrahepatic
obstruction
>10x URL
<10x URL
AST>AL
T
Dilated
ducts
Normal
ducts

27. Tests based on carbohydrate metabolism
1. Galactose tolerance test
2. Fructose tolerance test
• Galactose tolerance test
• Detect liver cell injury, measure intrinsic hepatic function, can be done in
jaundice
• Two types – Oral and IV
A. Oral
• Done in the morning after night fast
• Fasting sample as control
• 40 gm galactose in water given orally
• Sample taken half hourly for two hours along with urine sample for 5 hours

28. • Interpretation:
• <3gm excreted in urine within 3 – 5 hours, blood galactose returns to normal
within 1 hr – normal/obstructive
• Galactose Index:
• Adding up all the galactose values
• Interpretation:
• Upper normal limit – 160 mg/dL
• Liver diseases involving parenchyma - level ↑
Galactose tolerance test

29. Galactose tolerance test
B. IV galactose tolerance test
• Performed in the morning after a night’s fast
• Fasting blood sample taken as control
• IV galactose given – 0.5 gm/kg body weight dose as 50% solution
• Blood taken after 5 mins, and at 30 mins interval till 2.5 hrs.
• Interpretation:
• Curve begins at 200mg/dL, fall steeply to 0 – 10mg% at 2 hours
• In parenchymal disease – slow removal - >20mg% at 2.5 hr sample

30. Test based on changes in plasma proteins
1. Total plasma proteins and A:G ratio
• Liver is major source of blood proteins
• Exclusive source of albumin
• Major source of globulin

31. Interpretation:
• Infectious hepatitis (early stage) – Normal, ↑ beta globulin followed by ↑
gamma globulin
• Obstructive jaundice – Normal
• Parenchymal liver diseases - ↓ albumin, ↑ globulin – A:G  reversed
• Low albumin can cause oedema
• No change of albumin level – poor prognostic sign
Total plasma proteins and A:G ratio

32. Estimation of Plasma Fibrinogen
• Primary source of fibrinogen – Liver
• Normal - 200 – 400 mg%
• <100 mg% in parenchymal disease
Causes –
• Acute hepatic necrosis
• Poisoning from carbon tetrachloride
• Adv. Stage of cirrhosis

33. Prothrombin Time as a hepatic marker
• Liver converts preprothrombin in presence of Vit K
• Activity is measured as Prothrombin time (PT)
• PT is inversely related to conc. of prothrombin, factor V, VII, X
Interpretations:
• Always reported as factor or % of normal prothrombin time of control (11.0 –
12.5 seconds) - 0.85 to 1.1
• In parenchymatous liver disease - ↑ PT
• In obstructive jaundice - ↑ PT

34. Hepatic function test based on amino acid metab.
• Ammonia is generated from conversion of amino group of aa
• Process in known as deamination
• Utilised in urea cycle – exclusive in liver
• Interpretation:
• Normal - 10 – 80 mcg/dL (Adult), 40 – 80 mcg/dL (child), Newborn – 90 –
150 mcg/dL
• ↑ in parenchymatous liver disease. Very high value in hepatic coma.

35. Algorithm for assessing LFT
Abnormal LFT
Hepatocellular disease Cholestatic disease
Acute hepatitis Chronic hepatitis Acute cholestatsis Chronic cholestasis
USG/Percutaneous cholangiography
Intrahepatic cholestasis Extrahepatic cholestasis
AST>3X URL, ALP<2X URL AST<3X URL, ALP>2X URL
Normal
albumin
Decreased
albumin
Normal
albumin
Decreased
albumin