Liver function tests final

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

1. LIVER FUNCTION TESTS By Dr Prabhakar , 1 st year PG Dept of Pediatrics, Sri Venkateswara medical college, Tirupati .

2. Overview Introduction B iochemical tests Indications Limitations Interpretation Serological tests Radiological tests

3. Functions of Liver

4. 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

5. 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

6. 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

7. Normal ranges of B iochemical tests   T est   Normal range Aspartate transaminase (AST/SGOT) 5–40 IU /L Alanine transaminase (A L T/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

8. Indications These tests can be used to Detect presence of liver disease Distinguish among different types of liver disorders Gauge the extent of known liver damage Follow the response Routine checkup Drug usage

9. Liver enzymes Location of various liver enzymes

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

11. 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 . Liver enzymes are important markers of Liver injury…….NOT Liver function Accurate markers of severity of Liver disease M inor 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.

12. 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 ).

13. 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.

14. 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 .

15. 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. T hus 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 .

16. 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

17. 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

18. 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)

19. 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 .

20. 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.

21. 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.

22. 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.

23. 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.

24. 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 anticonvulsants like phenytoin, barbiturates. NNRTI and Protease inhibitors TCA anticoagulants like warfarin antihyperlipidemics analgesics.

25. 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 .

26. 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. .

27. Tests of liver synthetic capacity

28. 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

29. 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.

30. 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.

31. 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.

32. 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

33. 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.

34. 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.

35. 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

36. 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 .

37. 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.

38. 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

39. 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.

40. 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.

41. 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 S r.ammonia and level of hepatic encephalopathy have a poor correlation.

42. 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 .

43. 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.

44. 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.

45. 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.

46. 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.

47. 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.

48. Bilirubin metabolism

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

50. Classification of jaundice

51. Sites of cholestasis

52. Causes, clinical features and biochemical abnormalities

53. 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.

54. 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.

55. 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

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

57. Interpretation of LFT’s

58. 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 I nvestigations

59. Hepatitis serology

60. 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.

61. 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.

62. ERCP - A fibreoptic duodenoscope is passed in to 1 st 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.

63. 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.

64. 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.

65. -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.

66. 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.

67. -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.

68. 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.

69. 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.

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

71. 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.

72. 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

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

74. 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

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