Liver function tests

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Notes on Liver function tests.. By Dr. Ashish Jawarkar Contact: [email protected] Web: pathologybasics.wix.com/notes

Clinical pathology notes LIVER FUNCTION TESTS

by Dr. Ashish Jawarkar (M.D. Pathology) Consultant Pathologist

Parul Sevashram Hospital Vadodara

OVERVIEW

1. Indications of LFT 2. Limitations of LFT 3. Classification of LFTs

a. tests that assess excretory function i. bilirubin in serum and urine ii. urobilinogen in urine and feces

b. tests that assess synthetic function i. serum protein

ii. serum albumin iii. serum albumin:serum globulin ratio iv. Prothrombin time v. Serum protein electrophoresis

c. tests that assess metabolic function i. Blood ammonia level

d. tests that assess hepatic injury i. ALT/SGPT

ii. AST/SGOT iii. Alkaline phosphatase iv. Gamma GGT v. 5-nucleotidase

e. tests that assess clearance of exogenous substances i. Bromsulphathelien excretion test

4. Each LFT in detail 5. Interpretation of LFT 6. Approach to a patient with suspected hepatocellular disorder, cholestatic disorder

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* INDICATIONS OF LIVER FUNCTION TESTS

1. Screening of suspected liver disorder 2. to find out type of liver disease

a. hepatocellular b. cholestatic c. infiltrative

3. assess the severity and prognosis of liver disease 4. follow up the course of liver disease through the recovery phase

* LIMITATIONS OF LIVER FUNCTION TESTS

1. Lack sensitivity Liver has large anatomic and functional reserve; there has to be extensive liver damage for LFTs to derange

2. Lack specificity LFTs are abnormal in various non hepatic conditions:

a. raised bilirubin i. hemolysis ii. ineffective erythropoeisis

iii. large hematoma b. raised aminotransferases

i. muscle injury ii. alcohol abuse

iii. MI c. raised alkaline phosphatase

i. pregnancy ii. bone disorders

d. low serum albumin i. poor nutrition ii. proteinuria

iii. malabsorption iv. severe illness causing catabolism

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(i) BILIRUBIN: Serum Bilirubin Types:

Indirect Bilirubin (unconjugated) 90% more of total

Direct Bilirubin (conjugated) 10% or less of total

1. Tightly bound to albumin 2. water insoluble 3. not excreted in urine

1. includes bilirubin glucoronide, bilirubin diglucoronide and delta bilirubin#

2. water soluble 3. can be excreted in urine

# consists of conjugated bilirubin bound to albumin, level is increased in cholestasis, excreted slowly in urine

Method (Di azo method): Serum + di azo reagent Serum + diazo reagent + accelerator Pink Azobilirubin Pink azobilirubin + alkaline tartarate +alkaline tartarate Blue azobilirubin Blue azobilirubin Measure absorbance at 600nm Measure absorbance at 600 nm Total bilirubin Direct bilirubin Indirect bilirubin = total bilirubin – direct bilirubin

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Normal Levels:

Total Bilirubin 0.3-1.0 mg/dl Direct Bilirubin 0 – 0.2 mg/dl

Patterns:

Normal Direct 10% of total Post hepatic type Direct >50% of total Hepatic type Direct 20-50% of total Pre hepatic type Direct <15% of total

Urine bilirubin Rationale:

1. Presence of bilirubin in urine indicates conjugated hyperbilirubinemia due to obstructive or hepatocellular causes.

2. Bilirubin is absent in urine in hemolytic jaundice because unconjugated bilirubin is not soluble in water.

Methods:

1. Foam test

5 ml urine in test tube

shake Yellow foam

Bilirubin present

2. Gmelin’s test

3 ml conc nitric acid in test tube + pour 3 ml urine slowly over it

Play of colors from yellow to violet to blue to green

Positive test

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3. Lugol’s iodine

4 ml lugol’s iodine in test tube + 4 drops urine

shake

Green color indicates positive taste

4. Fouchet’s test

5 ml urine + 2.5 ml 10% BaCl2

Look for ppt formation

Obtain ppt on filter paper

Add 1 drop fouchet’s reagent

Blue green color immediately

Bilirubin is present

5. Reagent strips impregnated with diazo reagent

Can detect minimum 0.5 mg/dl of bilirubin Patterns:

Urine Prehepatic Hepatic Post Hepatic Bilirubin Absent Present Present Urobilinogen Increased Increased Absent

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(ii) URINE UROBILINOGEN Rationale:

Bile contains conjugated bilirubin

Converted by bacterial action in intestines to urobilinogen

Enterohepatic circulation

Some urobilinogen not taken up by liver is excreted in urine

On exposure to air (urine), urobilinogen is converted to urobilin which gives urine its pale yellow color

Method:

1. Ehrlich’s aldehyde test

5 ml urine + 0.5 ml Ehrlich’s aldehyde reagent 5 min, room temp

Pink color Dark red color Normal urobilinogen Increased urobilinogen Fallacy: This test is positive with urobilinogen, bilirubin and porphobilinogen. If bilirubin is suspected; before adding Ehrlich’s reagent, BaCl2 is added and ppt is removed, which removes the bilirubin and test is performed on the filterate.

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If Porphobilinogen is suspected – Watson-Shwartz test is performed

5ml urine + 0.5 ml Ehrlich’s aldehde reagent

Pink / Dark red solution

Add chloroform 1-2 ml

Pink color in aqueous layer Pink color in chloroform layer

Acqueous layer acqueous layer

Chloroform layer Chloroform layer

Porphobilinogen suspected Urobilinogen confirmed

Decant pink acqueous solution Add butanol Pink color in butanol layer Butanol layer Acqueous layer Indicates porphobilinogen

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2. Reagent strip method

On reagent strips, test area is impregnated with p-dimethylaminobenzal dehyde or 4-methoxy benzene tetrafluoroborate

Normal levels:

Normal 0.5-4mg in 24 hours Increased urobilinogen in urine Decreased urobilinogen in urine

Hemolytic jaundice, hemorrhage in tissues Obstructive jaundice, reduction of intestinal flora

Fallacy: False negative results may be obtained if -

1. UTI – oxidizes urobilinogen to urobilin 2. antibiotic therapy – eliminates gut bacteria, no urobilinogen produced

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(iii) Prothrombin time Rationale:

1. Most of the clotting factors (except vWF) are synthesized in the liver, hence clotting function would be deranged in liver disorders

2. Vitamin K dependent clotting factors include factor II, VII and IX, and X. PT measures the activity of II, VII and X.

Method:

Platelet poor plasma

+

Tissue thromboplastin (activates extrinsic pathway)

+

Calcium chloride

Allowed to clot

Note time Causes of raised PT:

1. Hepatocellular disease# 2. Obstructive jaundice# – malabsorption of vitamin K – lack of synthesis of vitamin K

dependent clotting factors 3. DIC – exhaustion of coagulation factors 4. Inherited deficiency of coagulation factors

# To differentiate raised PT due to hepatocellular disease or obstructive causes, repeat after administration of Vit K Normal values:

PT 11 To 16 seconds

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(iv) Serum Proteins 1. Total Proteins Rationale:

1. Liver is the sole site for synthesis of all proteins except gammaglobulins (which is synthesized by plasma cells).

2. Hence measurement of total proteins is a fair indicator of liver function 3. However, the decrease in proteins synthesized by liver is compensated by increased

synthesis of gamma globulins by plasma cells. 4. Hence overall value of total serum protein measurement is limited.

Methods: 1. Refractometer method: Refractive index of serum is measured and read directly from the refractometer 2. Biuret method:

Copper ions in the reagent react with peptide bonds of the protein

Violet color compound

Color intensity read by colorimeter Normal:

Total Protein 5.5 – 8 gm/dl

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2. Serum Albumin

Rationale:

1. Albumin consists of 60% of total proteins and is exclusively synthesized in liver. Hence its estimation can help in liver diseases (especially chronic). Serum albumin level is low in chronic liver diseases like cirrhosis and also correlates with severity like progression of ascites.

2. The half life of albumin is 20 days, hence its level does not fall with acute diseases such as acute hepatitis.

3. Serum albumin measurement is not specific because albumin also falls in a. Malnutrition b. Malabsorption c. Decreased sythesis – liver disease, chronic infection d. Increased catabolism – thyrotoxicosis, malignancies, infection e. Increased loss

i. Nephrotic syndrome ii. Burns

iii. Protein loosing enteropathy f. Increased blood volume (dilution – false low)

i. Pregnancy ii. CCF

Method: BROMOCRESOL GREEN METHOD;

Serum + Bromo cresol green

Binds to albumin

Blue color

Measured colorimetrically Normal Values:

Serum albumin 3.5 – 5 gm/dl (60% of total proteins)

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3. Serum albumin : Serum globulin ratio Rationale:

1. The total serum plasma protein level is affected by compensatory increase of gamma globulins as albumin falls

2. The ratio of serum albumin to globulin gives a better idea of the liver function Normal:

Normal albumin:globulin ratio >1:5 4. Serum Protein electrophoresis Following pattern can be observed on electrophoresis: Normal:

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Cirrhosis of liver:

When liver function is sufficiently diminished, protein synthesizing capacity is compromised and concentrations of albumin and proteins in the alpha and beta bands are decreased. An additional common finding is beta-gamma bridging due to increased IgA.

Beta-gamma bridging

Alb α1 α2 β γ

The Nephrotic Syndrome --

1. Renal disease involving the glomeruli is always associated with increased urinary protein loss. When protein loss is greater than 3-4 g/day, the protein synthesizing capacity of the liver is exceeded and hypoproteinemia, accompanied by anasarca, develops to cause the nephrotic syndrome.

2. The massive urine protein loss is due to increased permeability of glomeruli to protein. The permeability increase may be minimal so that only albumin and other smaller molecular weight proteins are selectively filtered (selective nephrosis, as in Minimal Change Disease) or may be greater so that larger proteins are also filtered (nonselective nephrosis, as in membranous golmerulonephritis) as is the case in the example shown.

3. Alpha-2-macroglobulin is sufficiently large so that it is not filtered and increased synthesis (from the general hepatic protein synthesis) causes its accumulation.

4. Lipoproteins are also sufficiently large to accumulate and hyperlipidemia is a characteristic of the nephrotic syndrome, although lipoproteins are not stained with the protein stain used in visualizing proteins.

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Normal Abnormal

Alb α1 α2 β γ

Alpha-1-Antitrypsin Deficiency:

A genetic defect causes a deficiency of alpha-1-antitrypsin. The antiprotease deficiency results in a propensity to develop emphysema. Since alpha-1-antitrypsin is the major component of the alpha-1 band, deficiency is suggested by a reduced alpha-1 band. Deficiency is confirmed by specific immunochemical quantification.

Normal

Abnormal

Alb α1 α2 β γ

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Acute Inflammation

The alpha-1 and alpha-2 bands are increased during the inflammatory response from increased hepatic synthesis of acute phase reactant proteins.

Normal

Abnormal

Alb α1 α2 β γ Chronic Inflammation --

Immunoglobulin synthesis by antigen activated B lymphocytes transformed to plasma cells is demonstrated by the increased polyclonal gamma band. Normal

Abnormal

Alb α1 α2 β γ

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Immunoglobulin Deficiency --

Deficient immunoglobulin synthesis is revealed by a markedly diminished gamma band. Effected individuals are prone to recurrent infection Monoclonal Gammopathy --

1. An unusually sharp band in the gamma region strongly suggests the presence of a homogeneous immunoglobulin and, thus, the malignant proliferation of plasma cells from a single cell (multiple myeloma) in contrast to the broad, heterogeneous, or polyclonal, gamma band as exhibited above in chronic inflammation from immunoglobulin synthesis by many different clones of plasma cells.

2. Homogeneous immunoglobulins are also found in Waldenstrom's macroglobulinemia (where the sharp gamma band is always IgM). Specimens which exhibit a narrow gamma band are further examined by immunofixation electrophoresis as described below

Alb α1 α2 β γ

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ImmunoFixation Electrophoresis

Immunofixation electrophoresis (IFE) is used to demonstrate that a narrow gamma band is due to a homogeneous immunoglobulin. IFE has superceded immunoelectrophoresis, results from which are considerably more difficult to interpret, for the purpose of evaluating monoclonal gammopathy.

In the illustration below, 6 replicates of the specimen are loaded on to separate lanes of an IFE gel. Following electrophoresis, the protein in each lane is stained differently. The first lane (SP) is stained for total protein. The protein in each of the other lanes is "stained" with specific antisera for immunoglobulin heavy and light chains, respectively, as illustrated in the figure. The finding of the preponderance of only one light chain associated with a predominantly staining heavy chain confirms the molecular homogeneity of the immunoglobulin and also provides identification. IFE identifies the narrow band as monoclonal IgG, lambda.

Sometimes malignant plasma cells synthesize excess light chains and less frequently

only light chains are synthesized. Almost never is excess heavy chain or only heavy chain synthesized. Excess free lambda light chain is exhibited in the illustration.

Serum IFE in monoclonal gammopathy

Free light chains are readily filtered by the glomeruli and often are not detectable in serum specimens. Excess light chain synthesis results in proteinuria, which exhibits a narrow band upon electrophoresis. The identity of the narrow band is determined by IFE and is here seen to be free lambda light chain. (A trace of monoclonal IgG,lambda is also present in the urine specimen). The bottom-most band is albumin.

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Urine IFE in monoclonal gammopathy

Polyclonal Gammopathy. An IFE of a serum specimen with a polyclonal gamma increase is shown for the sake of comparison.

Serum IFE

Broad bands are present for both IgG and IgA and corresponding kappa and lambda light chain bands. The light chains appear to be present at the normal kappa/lambda ratio of about 2.

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(v) Blood Ammonia Level Rationale:

1. Ammonia is detoxified and converted to ammonia in liver, estimation of blood ammonia is an indicator of metabolic function of the liver.

2. Estimation of blood ammonia helps in knowing the cause in patients of coma of unknown origin

3. Very nonspecific because it is also raised in a. Reyes syndrome b. Shunting of portal to systemic blood c. GI hemorrhage – increased production of ammonia d. Inherited deficiency of urea cycle enzymes

Normal:

Ammonia 9-33 micromol/l

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(vi) Serum aminotransferases (SGOT (AST) & SGPT (ALT)) ALT (cytosol) GGT Canalicular surface

Canalicular surface and microsomes

5’ nucleotidase ALP

LDH (cytosol) AST (mito and cytosol)

Location of liver enzymes

Rationale:

Normally these enzymes are present in serum at low levels

When necrosis or cell death occurs, these are released into the blood

Levels correlate with extent of tissue damage Normal levels:

AST / SGOT 5-40 U/L ALT / SGPT 5-42 U/L AST:ALT 0.7-1.4

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Patterns:

>15 times increase 1. Acute viral hepatitis 2. Toxin induced hepatocellular damage (CC l4) 3. Centrilobular necrosis due to ischemia (like CCF)

5-15 times increase 1. Chronic hepatitis 2. Autoimmune hepatitis 3. Alcoholic hepatitis 4. Drug induced hepatitis

Gradual decrease in enzymes Recovery from acute hepatitis Vs Massive liver necrosis

Hepatocellular jaundice Cholestatic jaundice AST and ALT increase >500 U/L AST and ALT increase <200 U/L

Alcoholic hepatitis Acute viral hepatitis AST:ALT > 2 AST:ALT <1

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(vii) Serum Alkaline Phosphatase (ALP) Rationale: 1. Alkaline phosphatase is present in canalicular surface of hepatocytes

Hence diseases that affect hepatocyte secretion have elevated ALPs

It is used primarily to differentiate between hepatocellular and cholestatic jaundice

No increased ALP Increased ALP

2. It is non specific – also secreted from a. bones b. intestine c. kidneys d. placenta Causes of raised ALP:

Cholestasis Increased >3 times

Bone diseases Pregnancy

1. Bile duct obstruction a. Ca head pancreas b. Bile duct strictures c. Biliary atresia 2. Biliary cirrhosis 3. PSC 4. infiltrative diseases of liver (granulomas, amyloid cysts)

1. Active bone growth in children 2. Osteomalacia 3. rickets 4. Hyperparathyroidism 5. Paget’s 6. Osteosarcoma 7. Osteoblastic metastasis

1. Placental ALP

Normal Levels:

Males: 25-120 U/L ALP Females: 25-90 U/L

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(viii) Serum GGT High levels also present in diseases of (organs with ducts)

- Pancreas - Kidney - Prostate

Causes of raised GGT:

1. Alcoholism – a. Marked elevation occurs in acute alcoholic hepatitis b. Also helpful in diagnosing occult alcoholism (with no notable liver damage)

2. Cholestasis – a. Level parallels ALP and 5’ Nucleotidase b. This enzyme is very helpful in combination with above two

3. Recovery from acute hepatitis – a. This is the last enzyme to return to normal following acute hepatitis –

decrease in level indicates favourable outcome Normal levels:

Males: upto 40U/L GGT Females: upto 25U/L

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(ix) 5’ Nucleotidase

a. Is released from liver only b. Used to know whether raised ALP is from liver or other sources

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(x) Dye Excretion test Rationale: a. Some synthetic dyes when introduced in the body are excreted in bile b. Their clearance depends on – hepatic circulation, hepatocyte function, uninterrupted bile

flow c. These are sensitive tests for liver function but not used nowadays because of risk of adverse

drug reactions d. Most common dyes used include

1. Bromsulphathlein (BSP) 2. Indocyanine green 3. Rose bengal

BSP Excretion test:

BSP injected IV

Taken up by hepatocytes

Conjugated to glutathione

Excreted in bile

Check for dye in blood at 45 min

If >50% retained – liver function is abnormal

Application:

@45 min in blood @2 hr in blood Dubin Johnson syndrome Normal value

(>50% excreted in bile) Higher than expected

(slow excretion after 45 min) Rotor syndrome High

(<50% excreted in bile) Lower than expected

(Fast excretion after 45 min)

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*INTERPRETATION OF LIVER FUNCTION TESTS Typical LFT values in:

Hepatocellular diseases Cholestatic diseases 1. Hyperbilirubinemia

Unconjugated>conjugated Ie indirect>direct Conjugated 20-50% of total

2. AST and ALT - >500 IU/L 3. ALP – raised <3 times 4. Usually no increase in GGT, 5’NT

1. Hyperbilirubinemia Conjugated>unconjugated Ie direct>indirect Conjugated >50% of total

2. AST, ALT- 200-500 IU/L 3. ALP – raised >3 times 4. elevation of GGT and 5’NT

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*APPROACH TO SUSPECTED HEPATOCELLULAR DISEASE:

Suspected hepatocellular disease (Higher indirect Bilirubin, clinically)

AST, ALT raised - >300IU/L

Acute hepatic injury

Acute Viral hepatitis Alcoholic hepatitis Toxic or ischemic injury Drug induced AST:ALT>2 AST,ALT>3000IU/L Acute hepatitis A Acute Hepatitis B Acute hepatitis C IgM Anti HAV IgM anti HBcAg Anti HCV HBsAg HCV RNA

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*APPROACH TO SUSPECTED CHOLESTATIC DISEASE Suspected cholestatic jaundice (High direct bilirubin, clinically)

Raised ALP

Evaluate GGT and 5’NT

Raised GGT, 5’NT Normal GGT, 5’NT Proves hepatic cause Non hepatic cause of Of raised ALP Raised ALP

Abdominal USG/CT Dilatation of bile ducts No dilatation of bile ducts Extrahepatic cause Intrahepatic cause Radiology Radiology a. PSC b. Ca head of pancreas c. Stricture Liver mass Diffuse Liver disease d. Stone in CBD FNAC Biopsy 1’ or 2’ Ca Infilatrative liver dis 1’ biliary cirrhosis

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Liver function tests