LIVER FUNCTION TESTS

Dr Anvesh narimetiPost graduate

(Md) Internal medicineGandhi medical college

OVER VIEW 1. Introduction2. Bilurubin 3. Aminotrasferases4. Alkaline phosphatases5. Synthetic functions6. Fibrosis markers7. Quantitative function8. Pattern recognition and bird eye view9. Clinical scenarios

The liver biochemical tests is preferreble term than liver function tests ?

It should be appropriately ordered with knowledge of history and physical examination of the patient.

They have potential to identify liver disease and distinguish among types of disorders, guage the severity, progression of dysfunction and also response to therapy

INTRODUCTION

Short comings of LFT

No test can accurately assess the liver’s total functional capacity

They measure only few functions among several functions performed by liver.

Singly they don’t have sensitivity and specifity so always battery of tests has to be performed to evaluate the liver

LIVER FUNCTION TESTS LIST

1. TOTAL BILURUBIN AND DIRECT AND INDIRECT FRACTION

2. ALANINE AMINOTRANSFERASE(ALT)3. ASPARTATE AMINOTRANSFERASE(AST)4. ALKALINE PHOSPHATASE(ALP)5. GAMMA GLUTAMYL

TRANSPEPTIDASE(GGPT)6. 5’NUCLEOTIDASE(5’NT)7. SERUM ALBUMIN8. PROTHROMBIN TIME

SPECIAL TESTS

QUANTITATIVE TESTS OF LIVER FUNCTION

TESTS TO ASSESS DEGREE OF HEPATIC FIBROSIS

BILURUBIN

Bilirubin is a breakdown product of heme About 4 mg/kg body weight of bilirubin is

produced each day Heme is converted to biliverdin by the

microsomal enzyme heme oxygenase. Biliverdin is then converted to bilirubin by the cytosolic enzyme biliverdin reductase.

Bilirubin formed in the reticuloendothelium is lipid soluble and virtually insoluble in water . This process of making insoluble to soluble by liver is called conjugation.

Vandenbergh Reaction The terms direct and indirect bilirubin, which correspond

roughly to conjugated and unconjugated bilirubin, respectively.

Test is called as vandenbergh test or diazo reaction. In this assay, bilirubin is exposed to diazotized sulfanilic

acid. The conjugated fraction of bilirubin reacts promptly, or

“directly,” with the reagent without the need for an accelerant ,and thereby allows measurement of the conjugated bilirubin fraction by photometric analysis within 30 to 60 seconds.

The total bilirubin is measured 30 to 60 minutes after the addition of an accelerant such as alcohol or caffeine.

The unconjugated, or indirect, fraction is then determined by subtracting the direct component from the total bilirubin.

Delta bilirubin, a conjugated bilirubin tightly linked to albumin through covalent binding.

Delta bilirubin is found in cases of prolonged and severe elevation of serum conjugated bilirubin levels.

Delta bilirubin has the half-life of albumin, approximately 14 to 21 days, which far exceeds the usual half-life of bilirubin in serum of 4 hours because of the strength of the covalent binding.

The identification of delta bilirubin explains why the decline in serum bilirubin in some patients with prolonged jaundice seems to lag behind clinical recovery.

Why some patients with conjugated hyperbilirubinemia do not have bilirubinuria.

DELTA BILURUBIN

Total serum bilirubin 1.0 -1.5 mg/dL, with 95% of a normal population falling between 0.2 and 0.9 mg/dL.

If the direct acting fraction is less than 15% of the total, the bilirubin can be considered to be entirely indirect.

The most frequently reported upper limit of normal for conjugated bilirubin is 0.3 mg/dL.

Indirect component 0.8-1.2 mg/dL.

Approach to the Patient with an Elevated Bilirubin Level

HYPER BILURUBINEMIA: It is due to 1. overproduction of bilirubin through

excessive breakdown of hemoglobin2. Impaired hepatocellular uptake3. Conjugation defect 4. Excretion of bilirubin5. Regurgitation of unconjugated and

conjugated bilirubin from damaged hepatocytes or bile ducts

Clinical pearls

Presence of conjunctival icterus suggests a total serum bilirubin level of at least 3.0 mg/dL but does not allow differentiation between conjugated and unconjugated hyperbilirubinemia.

Tea- or cola-colored urine may indicate the presence of bilirubinuria and thus conjugated hyperbilirubinemia

PATTERNS OF HYPERBILURUBINEMIA

Isolated elevation of the serum bilirubin level

Patient with an elevated bilirubin associated with elevated liver enzyme levels

Isolated elevation of the serum bilirubin level

Indirect Hyperbilirubinemia

Hemolytic Disorders Ineffective Erythropoiesis Drugs like Rifampin, Probenecid

impairs hepatocellular uptake. Inherited Conditions : Crigler-Najjar

syndrome types I and II and Gilbert’s syndrome causes Impaired conjugation of bilirubin.

Hematoma most common in neonates.

Direct Hyperbilirubinemia Inherited Conditions causing impaired

excretion of conjugated bilurubin. Dubin-Johnson syndrome  Rotor’s syndrome

AMINOTRANSFERASES The serum aminotransferases are most sensitive markers

of acute hepatocellular injury. ALT and AST catalyze the transfer of the α-amino groups of

alanine and L-aspartic acid, respectively, to the α-keto group of ketoglutaric acid.

AST, found in cytosol and mitochondria, is widely distributed throughout the body

AST is present in liver>cardiac muscle>skeletal muscle>kidney>brain>pancreas>lung>leukocytes>erythrocytes.

ALT, a cytosolic enzyme also found in many organs, is present in greatest concentration by far in the liver.

More specific indicator of liver injury is ALT

Increases in serum values of the aminotransferases reflect either damage to tissues rich in these enzymes or changes in cell membrane permeability that allow ALT and AST to leak into serum.

Hepatocyte necrosis is not required for the release of aminotransferases

The degree of elevation of the aminotransferases does not correlate with the extent of liver injury.

Aminotransferases have no function in serum and act like other serum proteins.

They are distributed in plasma and interstitial fluid and have half-lives measured in days.

Cleared by cells in the reticuloendothelial system, with AST cleared more rapidly than ALT.

Normal values for aminotransferases in serum vary widely among laboratories, but values gaining general acceptance are <30 U/L for men and <19 U/L for women

Upper values are determined by reference laboratories.

Approach to the Patient with an Elevated Aminotransferase Level

levels up to 300 U/L are nonspecific. Degree of elevation? Pattern of elevation (AST/ALT) Then have to be interpreted with

history and physical examination

marked elevations of aminotransferase (>1000 U/L)

Viral hepatitis (A to E) Toxin or drug-induced liver injury Ischemic hepatitis

•Autoimmune hepatitis•Acute Budd-Chiari syndrome•Fulminant Wilson disease•Acute obstruction of the biliary tract

Mild Elevations ALT > AST (<150 U/L or 5 × normal)

NAFLD AND NASH WILSONS DISEASE AUTOIMMUNE HEPATITIS CHRONIC VIRAL HEPATITIS HAEMOCHROMATOSIS MEDICATIONS AND TOXINS ALPHA 1 ANTITRYPSIN DEFICIENCY CELIAC DISEASE AND HYPERTYROIDISM

The ratio of AST to ALT in serum is helpful in the recognition of alcoholic liver disease.

If the AST level is less than 300 U/L, a ratio of AST to ALT of more than 2 suggests ,and a ratio of more than 3 is highly suggestive of alcoholic liver disease.

When a patient with chronic alcoholic liver disease sustains a superimposed liver injury, particularly acetaminophen toxicity, the aminotransferase level can be strikingly elevated, yet the AST/ALT ratio is maintained.

Mild Elevations,AST > ALT (<150 U/L, <5 × normal)

Hepatic Causes Alcohol-related liver injury (AST : ALT >

2 : 1, AST nearly always <300 U/L) CirrhosisNonhepatic Causes Hypothyroidism Macro-AST Myopathy Strenuous exercise

Severe, Acute Elevations, AST > ALT (>1000 U/L or >20-25 × normal)

HepaticCause Medications or toxins in a patient with

underlying alcoholic liver injuryNonhepatic Cause Acute rhabdomyolysis

AST to ALT ratio is typically less than 1 in patients with chronic viral hepatitis and nonalcoholic fatty liver disease (NAFLD), a number of investigators have observed that, as cirrhosis develops, the ratio rises and may become greater than 1.

The increase in AST/ALT ratio with the development of cirrhosis is believed to result from impaired functional hepatic blood flow, with a consequent decrease in hepatic sinusoidal uptake of AST.

Studies have shown that an AST/ALT ratio of greater than 1 as an indicator of cirrhosis in patients with chronic hepatitis C has a high specificity (94% to 100%)

ASYMPTOMATIC ELEVATIONS OF AMINOTRSFERASES

ALKALINE PHOSPHATASE The term alkaline phosphatase applies

generally to a group of isoenzymes distributed widely throughout the body.

Isoenzymes of greatest clinical importance in adults are in the liver and bone because these organs are the major sources of serum alkaline phosphatase.

Other isoenzymes originate from the placenta, small intestine, and kidneys.

In the liver, alkaline phosphatase is found on the canalicular membrane of hepatocytes; its precise function is undefined.

Alkaline phosphatase has a serum half-life of approximately seven days, and although the sites of degradation are unknown.

Clearance of alkaline phosphatase from serum is independent of either patency of the biliary tract or functional capacity of the liver.

Hepatobiliary disease leads to increased serum alkaline phosphatase levels through induced synthesis of the enzyme and leakage into the serum, a process mediated by bile acids

serum alkaline phosphatase level be checked in the fasting state because of intestinal alkaline phosphatase

Serum alkaline phosphatase values vary with age. Male and female adolescents have serum alkaline phosphatase levels twice the level seen in adults.

Level of serum alkaline phosphatase increases after age 30 years in both men and women, the increase is more pronounced in women than in men; a healthy 65-year-old woman has a serum alkaline phosphatase level 50% higher than that of a healthy 30-year-old woman

Pregnancy values are high.

Isolated elevation of the serum alkaline phosphatase level, the serum GGTP or 5′NT are used to distinguish a liver origin from bone origin of the alkaline phosphatase elevation.

A low serum alkaline phosphatase level may occur in patients with Wilson disease, especially those presenting with fulminant hepatitis and hemolysis, possibly because of reduced activity of the enzyme owing to displacement of the co-factor zinc by copper

Gamma Glutamyl Transpeptidase

GGTP is found in the cell membranes of a wide distribution of tissues including liver (both hepatocytes and cholangiocytes), kidney, pancreas, spleen, heart, brain, and seminal vesicles.

GGTP is not elevated in bone disease Use of serum GGTP levels is to identify the

source of an elevation in the serum ALP. Phenytoin, barbiturates,NNRTI and the

protease inhibitor abacavir causes elevation

Serum GGTP levels are also elevated in patients who drink alcohol so some experts have advocated use of the GGTP level for identifying unreported alcohol use(sensitivity 52-94%) low specificity.

For bile duct stones GGTP has high negative predictive value (97.9%).

5′-Nucleotidase 5′NT is associated with the canalicular

and sinusoidal plasma membranes. Primary role of the serum 5′NT level is

to identify the organ source of an isolated serum alkaline phosphatase elevation.

The 5′NT level is not increased in bone disease and is primarily increased in hepatobiliary disease.

CLINICAL PEARLS

Serum alkaline phosphatase elevation out of proportion to the level of the aminotransferases suggests a cholestatic disorder.

A four-fold elevation of the serum alkaline phosphatase is seen in both intrahepatic and extrahepatic cholestasis.

Approach to the Patient with an Elevated Alkaline Phosphatase

INTRA HEPATIC CHOLESTASIS

DRUGS – vanishing bile duct syndrome Primary biliary cirrhosis(PBC)-AMA

and liver biopsy. Primary sclerosing cholangitis

(PSC) association with inflamatory bowel disease.

Granulomatous liver disease-sarcoidosis.

Viral hepatitis-Epsteinbarr,CMV,Hep B&C

Genetic –1. Progressive familial intrahepatic

cholestasis-Type 1 (Byler’s disease),Type 2,Type 3

2. Benign recurrent intrahepatic cholestasis-Type 1&Type 2

Intrahepatic Cholestasis of Pregnancy

Total Parenteral Nutrition Graft-versus-Host Disease

EXTRA HEPATIC CHOLESTASIS

INTRINSIC & EXTRINSIC causes Requires CT and ERCP for evaluation Most common is choledocholitiasis,

malignacy, rarely parasitic infections Extrinsic causes like pseudocyst of

pancreas.

ASYMPTOMATIC ELEVATION OF ALKALINE PHOSPHATASE

TESTS FOR HEPATIC SYNTHETIC FUNCTION

Serum albumin Prothrombin time

Serum albumin Quantitatively accounts for 75% of the

plasma colloid oncotic pressure and is synthesized exclusively by hepatocytes.

Daily production nearly-15 g/day and has 300 to 500 g of albumin distributed in body fluids.

Half-life of albumin is 14 to 21 days makes it unreliable in acute liver failure.

Albumin synthesis is regulated by changes in nutritional status, osmotic pressure, systemic inflammation, and hormone levels.

Serum albumin levels less than 3 g/dL in a patient with newly diagnosed hepatitis should raise suspicion of a chronic process.

Check for other causes of hypoalbuminaemia.

Prothrombin Time

All clotting factors are produced in the liver except factor VIII, which is produced by vascular endothelial cells.

Prothrombin time is a measure of the rate at which prothrombin is converted to thrombin, reflecting the extrinsic pathway of coagulation.

Factors involved in the synthesis of prothrombin include II, V, VII, and X.

 

PROLONGED PT & INR

Hepatic parenchymal disease. Congenital deficiency of clotting factors Vitamin K deficiency. Disseminated intravascular coagulation HOW TO DIFFERENTIATE ?

prothrombin time allows an assessment of current hepatic synthetic function,as factor VII has the shortest serum half-life (six hours) of all the clotting factors.

It is also used for prognosis scores like MELD etc

The prothrombin time is not an accurate measure of bleeding risk in patients with cirrhosis because it assesses only the activity of procoagulant clotting factors, not anticoagulants such as protein C and antithrombin, the production of which is also reduced in cirrhosis.

TESTS TO DETECT HEPATIC FIBROSIS

liver biopsy is the standard for the assessment of hepatic fibrosis.

Need has arrived to go for non invasive tests.

Single serum biochemical markers that potentially reflect the activity level of hepatic fibrogenesis - Hyaluronan.

Hyaluronan is a glucosaminoglycan produced in mesenchymal cells and widely distributed in the extracellular space.

Typically degraded by hepatic sinusoidal cells

A fasting hyaluronan level greater than 100 mg/L (sensitivity83% & specificity78%)for the detection of cirrhosis in patients with a variety of chronic liver diseases like chronic hepatitis C, chronic hepatitis B, alcoholic liver disease, and nonalcoholic steatohepatitis.

FIBRO TEST(multiple parameters test)

It is the best evaluated among multiparameter blood tests.

The test incorporates 1. Haptoglobin2. Bilirubin3. GGTP4. Apolipoprotein A-I5. Alpha2-macroglobulin 

FIBROSpect II assay incorporates

1. Hyaluronate2. Tissue inhibitor of metalloproteinase 13. Alpha 2-macroglobulin.

FIBRO SCAN Transient elastography (TE) well known

as FIBRO SCAN. Uses ultrasound waves to measure

hepatic stiffness noninvasively. Principle behind the technique’s

development was 1. “fibrosis leads to increased stiffness of

the hepatic tissue”2. “A shear wave would propagate faster

through stiff material than through elastic material”.

The ultrasound transducer emits a low-frequency (50 Hz) shear wave, and the amount of time required for the wave to go through a set “window” of tissue is measured.

The window of tissue is 1 cm by 4 cm, 100 times the area of an average liver biopsy

Magnetic resonance elastography

MRE is another noninvasive technique under study.

The shear elasticity of the liver is measured after low-frequency (65 Hz) waves are transmitted into the right lobe of the liver.

In one study MRE was found to be superior to TE for staging liver fibrosis in patients with a variety of chronic liver diseases.

Quantitative Liver Function Tests Developed in the hope of evaluating

the excretory or detoxification capacity of the liver more specifically.

Lack of specificity and often cumbersome methodology have limited their widespread acceptance.

1. Indocyanine Green Clearance2. Galactose Elimination Capacity3. Caffeine Clearance4. Lidocaine Metabolite Formation5. Aminopyrine Breath Test

PATTERN RECOGNITION

BIRD EYE VIEW

CLINICAL SCENARIOS

NORMAL RANGES1. TOTAL BILURUBIN - 0.3-1.3 mg/dl2. DIRECT - 0.1-0.4 mg/dl3. INDIRECT - 0.2-0.9 mg/dl4. AST - 12- 38 IU/ml5. ALT - 7- 41 IU/ml6. TOTAL PROTEINS- 5.5 -9.0 gm/dl7. ALBUMIN – 3.5- 5.5 gm/dl8. Globulin – 2.0- 3.3 gm/dl

Scenario 1 A 30-year-old man is referred for

evaluation of elevated serum aminotransaminase levels.patient weighed 103.5kg during his high school, 112.5kg after graduation. 135kg 5 years later. Results of all liver tests are normal except for a serum AST level of 65U/L and a serum ALT level of 80U/L.

1) APPROACH TO THIS CASE

Scenario 2

A 30-year-old man has severe flu symptoms for 5 days. Cough, myalgia, headache, and anorexia have resulted in markedly diminished intake of food and liquid. He has been ingesting crocin tablets 3.5g/day. He was found to have a serum AST level of 5,000U/L and an ALT level of 5,500U/L.

Cause ?

Scenario 3

A 28-year-old man who has had ulcerative colitis for 10 years is found through routine screening to have a serum alkaline phosphatase level of 500U/L. Results of all other liver tests are normal.

1. What is the possible diagnosis?2. Investigation of choice?

Scenario 4A 17-year-old boy is referred for

evaluation of hepatomegaly and jaundice. On examination he is found to have a tremors

What are these tremors ? Investigations of choice in this patient?

Scenario 5

A62-year-oldwoman has pruritus and is found to have jaundice. Except for scleral icterus, the findings of the physical examination are normal.

The liver span measures 12cm at percussion. Liver tests reveal the serum bilirubin level to be

6.0mg/dL, AST, 280U/L , ALT 300U/L, serum alkaline phosphatase, 500U/L .

prothrombin time and normal serum albumin and globulin levels.

1. Pattern of liver enzymes elevation?2. Next investigation of choice?

Scenario 6 A 40-year-old woman is admitted to hospital for

therapy for alcohol withdrawal and impending delirium tremens.Laboratory studies reveal

1. serum bilirubin 2.0mg/dL, 2. serum AST-225U/L3. serum ALT-45U/L4. Prothrombintime-14seconds(INR-1.3)5. Serum iron level -170ug/dL(50-150ug/dl)6. Total iron-binding capacity- 200ug/dL(250-370)7. Iron saturation-85%(22-46%)8. Serum ferritin- 700ug/L. (50-150).

how to interpret above liver functions.

REFERENCES Sleisenger and Fordtran’s

gastrointestinal and liver diseases 9th edition.

Schiff’s diseases of the liver 11th edition Goldman’s cecil medicine 24th edition Harrisons principles of internal

medicine 18th edition Robbins and cotran pathology 8th

edition