Liver function tests final

LIVER FUNCTION
TESTS
BY DR PRABHAKAR, 1ST YEAR PG
DEPT OF PEDIATRICS,
SRI VENKATESWARA MEDICAL COLLEGE,
TIRUPATI.

Overview
 Introduction
 Biochemical tests
 Indications
 Limitations
 Interpretation
 Serological tests
 Radiological tests

Liver function tests
 Liver function tests (LFT’s) are groups of laboratory blood
assays designed to give information about the state of
patients liver
 They include
 Liver enzymes (SGOT, SGPT, ALP, GGT etc.,)
 Bilirubin(Direct and indirect)
 Albumin
 Prothrombin time / INR

 Some tests are associated with FUNCTIONALITY (e.g.
PT/INR, Albumin, Bilirubin),
 some with CELLULAR INTEGRITY (e.g. transaminases) and
 some with conditions linked to BILIARY TRACT (GGT and
ALP)
LFT- A misleading term,
firmly inserted in medical
vocabulary

Biochemical tests - implications
Biochemical test Clinical implication of abnormality
• Alanine amino transferase
• Aspartate aminotransferase
• Bilirubin
• Alkaline phosphatase
• Prothrombin time
• Albumin
• Gamma-glutamyl transferase
• 5’ nucleotidase
• Hepatocellular damage
• Hepatocellular damage
• Cholestasis, impaired conjugation
Or biliary obstruction
• Cholestasis, infiltrative disease or
biliary obstruction
• Synthetic function
• Synthetic function
• Cholestasis or biliary obstruction
• Cholestasis or biliary obstruction

Normal ranges of Biochemical tests
Test Normal range
Aspartate transaminase (AST/SGOT) 5–40 IU/L
Alanine transaminase (ALT/SGPT) 5–35 IU/L
Alkaline phosphatase 35–130 IU/L
Gamma-glutamyl transpeptidase (g-GT) 10–48 IU/L
Albumin 3.5–5.0 g/dL
Prothrombin time (PT) 12–13 s
Bilirubin
Total
conjugated
0.3-1 mg/dL*
<0.2 mg/dL

Indications
 These tests can be used to
1. Detect presence of liver disease
2. Distinguish among different types of liver disorders
3. Gauge the extent of known liver damage
4. Follow the response
5. Routine checkup
6. Drug usage

Liver enzymes
Location of various liver enzymes

Transaminases
Transaminases or aminotransferases are enzymes that catalyse a
transamination reaction between an amino acid and an α-keto acid.

 AST - heart, skeletal muscle, brain,
pancreas, lung, RBC and kidney.
 20% cytosolic and 80 %
mitochondrial
 serum half life of 17 hrs.
 ALT is more specific
 Low concentrations in kidney and
skeletal muscles
 serum half life of 47 hrs.
1. Liver enzymes are
important markers of Liver
injury…….NOT Liver
function
2. Accurate markers of
severity of Liver disease
3. Minor changes in values
have no prognostic
significance.
 AST is relatively more specific for chronic liver disease and alcoholic liver disease and
ALT for acute liver disease.
 Normal ratio is 0.7 to 1.4.
 De Riti’s ratio: In alcoholic hepatitis, the AST:ALT ratio is always 2:1. The ratio is
usually <1 in patients with acute and chronic nonalcoholic hepatitis.

 Most marked elevations of ALT and AST (>15 times
normal) are seen in
 acute viral hepatitis,
 toxin-induced hepatocellular damage
(e.g. carbon tetrachloride and
 centrilobular necrosis due to ischemia
(congestive cardiac failure).

 Moderate elevations (5-15 times) occur in
 Chronic hepatitis,
 autoimmune hepatitis,
 alcoholic hepatitis,
 acute biliary tract obstruction, and
 drug-induced hepatitis.
 Mild elevations (1-3 times) are seen in
 cirrhosis,
 nonalcoholic steatosis, and
 cholestasis.

 Fluctuating levels of transaminases may be seen in
hepatitis C infection
 A sudden fall in transaminases in a sick jaundiced patient is
indicative of bad prognosis as seen in acute fulminant
hepatitis.
 In anicteric hepatitis and inapparent hepatitis the only
biochemical abnormality may be an elevated ALT or AST.

Diagnostic value of transaminases
The first laboratory abnormality detected in early phase of
viral hepatitis is elevated transaminases.
 In hepatitis, elevation of transaminases precedes that of
bilirubin by about one week. Thus transaminases may be
declining as serum bilirubin is increasing in uncomplicated
hepatitis.
During recovery phase of viral hepatitis, there is a steady
fall in level of transaminases.

Secondary elevation of transaminases or their persistent
elevation indicates recrudesence of hepatitis or
development of chronic hepatitis.
Absolute elevation is of little prognostic value in predicting
the outcome of acute hepatitis

ALKALINE PHOSPHATASE
 Serum alkaline phosphatase (ALP) activity refers to group of
isoenzymes that hydrolyse organic phosphate esters at alkaline pH to
inorganic phosphate and an organic radical.
 Sources of ALP
Liver - canalicular membrane
Bone - osteoblasts
Small intestine - brush border of enterocytes
Kidney - proximal convoluted tubules
Leukoytes
Placenta

Hepatobiliary causes of increased alkaline
phosphatase are:
 Bile duct obstruction (cancer of head of pancreas, stone in
common bile duct, stricture of bile duct, biliary atresia)
 Primary biliary cirrhosis
 Primary sclerosing cholangitis
 Infiltrative diseases of liver (granulomatous diseases like
tuberculosis or sarcoidosis, amyloidosis, cysts, primary or
secondary cancer)

 ALP is present within osteoblasts.
Due to high osteoblastic activity during active bone growth,
serum ALP is higher in children than in adults.
 Serum ALP is increased during pregnancy due to secretion from
placenta
 increased osteoblastic activity
 osteomalacia,
 rickets,
 hyperparathyroidism,
 Paget’s disease, osteosarcoma, and
 osteoblastic type of metastaticcarcinoma.

 Bone isoenzyme is heat labile compared hepatic ALP which is
relatively heat stable. They can also be differentiated by
polyacrylamide gel electrophoresis.
 The most practical method to decide whether a high serum ALP is
due to liver disease is by measuring another enzyme which rises in
cholestatic disease and that is more specific to liver like GGT or 5’-
Nucleotidase.
 Zinc is a cofactor for ALP and in conditions causing zinc deficiency,
ALP may be reduced.

 Mechanisms that contribute to raised levels of ALP are
 1)regurgitation from hepatocytes
2) increased synthesis
 Dissociated jaundice – In incomplete biliary obstruction or
when intrahepatic obstruction is only partial, bilirubin may
be normal or only slightly elevated while ALP is quite high.
This is seen in space occupying lesions like metastasis.

 Diagnostic value of ALP
 serum ALP is elevated in following conditions
1)elevated more than 5 times above normal in
cholestasis both intrahepatic and
extrahepatic.
2)lesser degrees of elevation, up to 3 times the
normal are seen in all types of liver
disorders.

GAMMA GLUTAMYL
TRANSPEPTIDASE
 It is synthesized by epithelium of small bile ductules and
hepatocytes.
 The primary use of serum GGTP levels is to identify the source of
an isolated elevation in the serum ALP level; GGTP is not elevated
in bone disease
 This is one of the most sensitive tests for presence of hepatobiliary
disease and similarly absence of raised GGT correlates well with
absence of hepatic metastasis.
 GGT levels are higher in biliary tract disease and cholestasis than in
hepatocellular disease.

 An elevated GGT is used to confirm that a raised ALP is of
hepatobiliary origin. Hence it is a more sensitive marker
compared to ALP.
 The following drugs may elevate GGT giving rise to false positive
diagnosis of hepatobiliary disease
1. anticonvulsants like phenytoin, barbiturates.
2. NNRTI and Protease inhibitors
3. TCA
4. anticoagulants like warfarin
5. antihyperlipidemics
6. analgesics.

 An isolated raise in GGT is an early indicator of alcohol
consumption in otherwise healthy children.
 Recovery in acute hepatitis: Serum GGT is the last enzyme
to return to normal following acute hepatitis and its
normalization is indicative of a favourable outcome.

5’ - NUCLEOTIDASE
 This enzyme is found in liver, intestine, heart, blood vessel
& endocrine pancreas.
 5′NT is associated with the canalicular and sinusoidal
plasma membranes; its function is undefined.
 As with GGTP, the primary role of the serum 5′NT level is to
identify the organ source of an isolated serum ALP elevation
The 5′NT level is not increased in bone disease and is
primarily increased in hepatobiliary disease..

Tests of liver synthetic
capacity

Hepatocytes manufacture a number of proteins, which are released in
to plasma like albumin, fibrinogen, alpha 1 antitrypsin, haptoglobin,
ceruloplasmin, transferrin, prothrombin etc. Hence reduced levels of
these reflect a decline in synthetic capacity of liver.
 Of these, ceruloplasmin,fibrinogen,alpha 1 antitrypsin and
haptoglobin are acute phase reactants. Their serum levels may be
raised when the patient has acute hepatitis.
Albumin and other proteins

 Liver is the sole site for the synthesis of most of the plasma
proteins, except gamma globulins which are synthesized by
plasma cells. Concentration of total serum proteins is about
5.5 to 8.0 gm/dl,
while that of serum albumin is 3.5 to 5.0 gm/dl. Serum albumin
comprises about 60% of total serum proteins
Tests for proteins in liver disease include
 Total serum proteins,
 serum albumin,
 calculation of serum albumin/globulin ratio (normal ratio is
>1.5), and
 Serum protein electrophoresis.

SERUM ALBUMIN
 Albumin is synthesized exclusively in liver and constitutes
about 60% of total proteins in serum; therefore its
estimation is an important investigation in liver disease.
 Half-life of albumin is about 20 days and therefore fall in its
level in response to decreased synthesis is not immediately
apparent.

Causes of decreased serum albumin:
 Decreased intake: malnutrition.
 Decreased absorption: malabsorption syndromes.
 Decreased synthesis: liver disease, chronic infections.
 Increased catabolism: fever, malignancy, infections.
 Increased loss: nephrotic syndrome, severe burns, protein-
losing enteropathies, ascites
 Increased blood volume: congestive cardiac failure.
As low serum albumin occurs in diseases other than those of
liver, serum albumin is a sensitive but nonspecific test for liver
disease.

 Most of the coagulation proteins are synthesized in the
liver. Vitamin K is required for the synthesis of
factors II, VII, IX, and X by the hepatocytes;
therefore these factors are called as vitamin K-dependent
factors.
 Synthesis of these factors is deficient in hepatocellular
disease. In obstructive jaundice, vitamin K (a fat-soluble
vitamin) cannot be absorbed due to the absence of bile in
the intestine.
PROTHROMBIN TIME

 PT is measure of time it takes for prothrombin to be
converted to thrombin in the presence of tissue extract,
calcium ions and activated factors V, VII,X.

 PT measures three out of four vitamin K-dependent factors
(II, VII, and X) and is prolonged in hepatocellular disease
and in obstructive jaundice.
 The result of reaction that produced thrombin is expressed
in seconds or as a ratio of plasma PT to a control PT.
 Normal values are 12-13 seconds.
 Prolongation of more than 2 sec is considered pathologic
and values >3 sec above normal indicate risk of bleeding.

 Activated factor VII is the key enzyme of extrinsic pathway as it has
shortest half life.
 Patient with early liver disease may present with an isolated
prolonged PT.
 A prolonged PT also suggests a poor prognosis in chronic liver
disease, this along with decreasing serum albumin is the most
important parameter to decide on liver transplantation

 To distinguish between a prolonged PT due to
Hepatocellular disease from that due to cholestasis with fat
malabsorption, PT is repeated after administration of
vitamin K.
 Reduction of prolonged PT occurs in cholestatic liver
disease, but not in hepatocellular disease.

 In a patient with liver disease PT may also prolonged due to
non hepatic causes other than vitamin K deficiency like DIC.
 Factor VIII is also synthesized from non hepatic sources like
vascular endothelium hence its level is usually normal in
liver disease, unless it is being consumed as in DIC. Thus
factor VIII level may help to differentiate hemorrhage due
to severe liver disease alone from that due to
accompanying DIC.

INTERNATIONAL NORMALIZATION RATIO (INR)
 This system standardizes the PT for different thromboplastin
reagents thus providing a universal standard by which to compare
any given lab result with that of WHO standard.
INR = (patients PT / normal PT)
ISI = International sensitization index
(provided with each batch of thromboplastin reagent)
 Liver biopsy is contraindicated if INR is >1.3
 PT/INR helps to monitor patients on warfarin therapy
ISI

 Advantages of using INR system
1)Easier, smoother regulation of anti - coagulation.
2)Travelling patients will have a standard, regardless of lab
used.
3)Standardization of laboratory and research efforts.
4)Reduced risks of complications associated with higher
doses of anticoagulants.

Diagnostic value Of Prothombin Time
1)It helps to differentiate cholestatic from hepatocellular jaundice.
2)It is not a sensitive index of liver disease, as even with severe form
of cirrhosis, it may be normal or slightly prolonged.
3)It is of high prognostic value especially in acute hepatocellular
jaundice.
4)A prolonged PT is not specific for liver disease as it may be seen in
congenital deficiencies of coagulation factors and also in acute
conditions like DIC and ingestion of drugs that effect prothombin
complex.

SERUM AMMONIA
 The concentration of ammonia in blood is regulated by balance of its
production and clearance.
 It is produced in colon by action of bacterial urease on dietary proteins and
aminoacids.
 Ammonia is converted by liver in to urea and then into glutamine by urea
cycle.
 The liver removes 80% of portal venous ammonia in a single pass.
 Normal levels of s.ammonia is 11-35 micro moles/L
 In chronic liver disease and portal hypertension ,large amounts of ammonia
bypass liver and reach brain, contributing to hepatic encephalopathy.
 However Sr.ammonia and level of hepatic encephalopathy have a poor
correlation.

SERUM LIPIDS AND
LIPOPROTEINS
 Lipids and lipoproteins are mainly synthesized in liver except
chylomicrons, which are synthesized in intestine.
 Liver diseases significantly affect serum lipids and lipoprotein levels.
 Serum cholesterol is increased in cholestatic jaundice. Skin xanthomas
develop if elevated 5 times above normal.
 An abnormal lipoprotein, Lipoprotein X is synesized in biliary atresia
and neonatal hepatitis. Following cholestyramine therapy, level
decreases in neonatal hepatitis, where as continues to be high in
biliary atresia.

TESTS OF QUANTITATIVE
FUNCTION
 These tests are complex and are done only in research labs. These
include
1)Galactose elimination test - galactose is taken up by liver and
converted to galactose I phosphate by glactokinase, which is the
rate limiting reaction in galactose elimination from blood.
Galactokinase activity depends on functional liver mass. Hence
galactose elimination gives an estimate of functional hepatic cell
mass.

2)Breath test – Aminopyrine labelled with c14 is given orally. It is
metabolised by cytochrome p-450 dependent demethylation to co2
in only liver. samples of 14co2 are collected from the mouth for 2
hrs. The expired 14co2 correlates with rate of disappearence of
radioactivity from plasma. The test reflects the residual functional
microsomal mass and viable hepatic tissue.

3)MonoEthylGlycineXylinide test (MEGX Test) - MEGX is the
main metabolite of Lignocaine formed in hepatocyte
microsomes by cytochrome p450dependent demethylation.
Lignocaine is given IV and serum MEGX is measured at 15
min and 30 min. Its level is decreased in cirrhosis compared
to control. MEGX test is useful to assess the quality of organ
donors. It is much superior to conventional LFT in predicting
graft survival.

SERUM BILIRUBIN
 Bilirubin, a tetrapyrrole pigment, is a breakdown product of
ferroprotoporphyrin IX.
 It’s level confirms jaundice, and used to assess the prognosis.
 It’s level represents the balance between input from production and
hepatic removal of the pigment.

 Unconjugated hyperbilirubinemia is due to overproduction
or impaired uptake or conjugation of bilirubin.
 Conjugated hyperbilirubinemia is due to decreased
excretion or backward leakage of the pigment.
 Serum bilirubin (S.Bb) is not a sensitive indicator of hepatic
dysfunction and may not accurately reflect the degree of
liver damage because an increase in Serum albumin may
induce a temporary shift of bilirubin from tissue sites in to
circulation.

Unconjugated vs Conjugated bilirubin
properties Unconjugated Bb Conjugated Bb
Water solubility insoluble soluble
Lipid solubility soluble insoluble
Vandenbergh
reaction
indirect direct
Binding to
albumin
++++ +

Causes, clinical features and biochemical
abnormalities

URINE UROBILINOGEN
 UBG is formed in terminal ileum and colon from conjugated Bb by
Clostridium ramosum, helped by E.coli.
 UBG excreted in stool is called stercobilinogen. It is converted by
colonic bacteria to stercobilin which imparts the normal brown
colour of stools. Hence in cholestatic jaundice stools are pale as Bb
can not reach the gut and hence stercobilin is not formed.
 About 20% of UBG is reabsorbed and undergoes enterohepatic
circulation.

 Increase in UBG in urine is found in hepatitis as damaged
hepatocytes are not able to reexcrete the UBG absorbed from gut. It
is thus a good index of hepatocellular dysfunction, often when other
tests are normal.
 Urine UBG is increased in following conditions 1)hepatitis
2)malignant disease of liver 3)cirrhosis 4)hemolytic anaemia
5)circulatory failure 6)pyrexia 7)severe constipation.

 UBG is absent in following conditions
1)complete biliary obstruction
2)severe bilirubin glucoronyl transferase
deficiency as seen in CN syndrome type I.
3)severe diarrhoea
4)prolonged antimicrobial treatment

URINE ABNORMALITIES IN JAUNDICE
Type of
jaundice
Urine bilirubin Urine
urobilinogen
Hemolytic
jaundice
nil +++
Hepatocellular
jaundice
+++ +++
Cholestatic
jaundice
+++ nil

Think about non
hepatic causes
Look at pattern
of abnormality
Hepato-cellular
Vs
cholestatic
Look at tests of
function
Acute vs Chronic
Classify the
abnormality
• HC vs Cholestatic
• Massive HC injury
• Evidence of
functional
abnormality
Consider DD
most common
and most
treatable
Correlate clinically
History
Physical examination
Investigations

RADIOLOGY
 PLAIN RADIOGRAPH OF ABDOMEN - It will give an indication of size
of liver and spleen. However it is rarely of diagnostic value and
hence not used frequently.
 ULTRASONOGRAPHY OF ABDOMEN - It provides information about
size of liver, spleen, pancreas, kidney and gallbladder. It detects gall
stones, tumors, hemangiomas, abscess and cysts with in liver. It
allows targeting of lesions for liver biopsy.
 A small or absent gallbladder after fasting suggest either severe
intrahepatic cholestasis or biliary atresia in a neonate. An enlarged
gallbladder may suggest primary sclerosing cholangitis.

 CT SCAN – it is helpful for detection and biopsy of hepatic tumors
and space occupying lesions. IV contrast causes enhancement of
vascular lesions and wall of abscesses and helps in differentiation of
tumors from other solid masses.

 ERCP - A fibreoptic duodenoscope is passed in to 1st part of
duodenum, ampulla of vater is identified, the pancreatic and biliary
ducts are cannulated and contrast is injected. This is very useful in
evaluation of extrahepatic liver disease in older children like
choledochal cysts, PSC and chronic pancreatitis. It is technically very
difficult in neonatal cholestsis.
It can also be used to
remove CBD stones and
for insertion of biliary stents.

 Percutaneous Transhepatic Cholangiography (PTC) - It is useful for
identification of biliary disease, if intrahepatic bileducts are dilated
secondary to obstruction and ERCP is impossible or unsuccessful. A
thin needle (Chiba needle) is passed through liver, the bile ducts or
gallbladder is punctured and radiological contrast is injected.
External drainage of biliary tree, dilatation of biliary strictures and
the introduction of biliary stents are all possible using this
procedure.

 Hepatobiliary Scintigraphy
-The development of soluble radioisotopes (technicium
trimethyl I bromo iminodiaceic acid) which are taken up
well by hepatocytes despite elevated Bb levels have been
utilized to either hepatic uptake or biliary excretion.
-Pretreatment with phenobarbitone (5mg/kg) for 3-5 days
prior to investigation improves hepatic uptake of isotope.

-It is most useful in assessment of biliary excretion in DD of
neonatal cholestasis. Under normal conditions biliary
excretion is completed in 4 hrs.
-Delayed excretion or no excretion after 24hrs suggests
severe intrahepatic cholestasis or EHBA.
-It is of some value in diagnosis of hepatic vein obstruction
(Budd Chiari syndrome) as poor uptake of liver is
demonstrated in most of liver except in caudate lobe which
has got separate venous drainage.

 ANGIOGRAPHY – Visualisation of coeliac axis, hepatic and
splenic blood vessels is obtained by femoral artery
catheterization and injection of radiological contrast. This
techniqhe has 2 parts.
-Arterial phase, which provides information about coeliac
axis, hepatic and splenic artery abnormalities,
vascularization and anatomy of hepatic tumors, hepatic
hemangiomas or detection of hepatic artery thrombosis.

-Venous phase, provides information about patency of
portal, splenic and superior meseteric veins and the
presence of portal hypertension and identification of
mesenteric, esophageal or gastric varices.
-Femoral artery spasm or thrombosis is an occasional side
effect, but rarely requires operative treatment.

 Splenoportography – here splenic and portal radicles are
visualised by injection of contrast into spleen, it has largely
been replaced by hepatic angiography.
 MRI – It has now replaced hepatic angiography as best way
to stage or diagnose hepatic tumors and to identify their
vascular supply.
-It may provide valuable information about liver or brain
consistency and storage of heavy metals.

The recent development of MRCP, in which both intra and
extrahepatic biliary ducts, and also the pancreatic duct may
be detected, may replace ERCP as a diagnostic investigation.

LIVER BIOPSY
 The diagnosis of most liver diseases requires histological
confirmation and thus liver biopsies are a routine procedure
in specialist centres.

Indications
• unexplained hepatomegaly
• unexplained jaundice
• unexplained elevation of liver enzymes
• cholestatic liver disease – biliary atresia and neonatal hepatitis
• cirrhosis
• chronic hepatitis
• drug related hepatitis
• infections of liver like TB
• enzyme analysis for IEM
• copper estimation in wilson disease when other tests are
equivocal
• post liver transplantation to assess acute rejection.

 Contraindications
 PT >3sec or prolonged or INR >1.3
 thrombocytopenia - PLC <60,000
 presence of grossly dilated bile ducts
 angiomatous malformations of liver
 hydatid cysts
 severe ascites

 Complications
 hemorrhage
 intrahepatic hematoma
 hemobilia
 pleurisy and perihepatitis
 development of AV fisthula
 biliary peritonitis
 puncture of other organs
 infection

SUMMARY
 State of liver rather than function alone
 Done as a group
 Indications and limitations
 Non hepatic causes to be kept in mind
 Interpret with clinical correlation
 Serological, Radiological and histological tests

References
 Sheila Sherlock Liver and biliary diseases
 Nelson Textbook of Pediatrics - 20e
 IAP Text book of Pediatrics 6th Ed
 Essentials of Clinical Pathology – Kawthalkar

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