LIVER FUNCTION TESTS

2. LIVER FUNCTION TESTS By Prof. Dr. Kefaya El-Sayed Mohamed Professor of Clinical Pathology, (Clinical Chimstry) Clinical Pathology Dep. Faculty of Medicine, Mansoura University

3. 1-Circulatory function: • Transfer blood from portal to systemic circulation. • Immune mechanism (RECs in the liver). • Regulate blood volume (blood storage). • Blood formation in faetus and anemic condition & also it stores antianemic factors). • Blood coagulation : Synthesis of clotting factors .

4. 2- Excretory Function: • Bile Function and excretion into intestine. • Bilirubin conjugates. • Bile salts. • Cholesterol. • Excretion of substance into blood. • Heavy metals. • Alkaline phosphatase. • Dyes.

5. 3-Metabolic Functions: • The liver is the central organ for metabolism of : • Carbohydrate: glycogenesis, gluconeo-genesis, glycogenolysis. • Protein: deamination of blood ammonia (urea formation) protein synthesis (plasma protein and coagulation factors). • Lipids: cholesterol, bile salts formation and secretion and VLDL with synthesis of apolipoprotein.

6. Formation of ketone bodies from fat, protein and pyruvic acid. • Minerals: e.g iron, copper, zinc, Mg. • Vitamins: A, K, B12 and vit. D.

7. 4- Detoxication Function : • Liver cells detoxify metabolic products (bilirubin, hormones, NH3) and toxic substances by the following: • Kupfer, cells: phagocytose foreign bodies. • Conjugation with glucuronic acid, glycine, cysteine, sulphate, glutamine, acetate and glutathione. • Demethylation, hyolrlysis, hyolroxylation and carboxylation. • Oxidation and reduction processes.

8. The biotrans formation of foreign compounds (e.g. Drugs) this biotransformation consists of two phases. Phase I involves oxidation or other reations that introduce a polar group into the molecule. Phase II consists of conjugation of the product of phase I or the original compound, if it already has a polar group, with glucuronate, glycine, or other moieties (e.g. aminopyrine, lidocaine, indocyanine green, caffeine and galactose).

9. Aim of Liver Function Tests: • Detection of liver disease. • D.D. of jaundice. • Severity and degree of liver damage. • Diagnosis of occult liver diseases.

10. A number of pitfalls can be encountered in the interpretation of common blood liver function tests: • These tests can be normal in patients with chronic hepatitis or cirrhosis. • The normal range for aminotransferase levels is slightly higher in males, and obese persons. • Severe alcoholic hepatitis is sometimes confused with cholecystitis or cholangitis.

11. Patients who present soon after passing common bile duct stones can be misdiagnosed with acute hepatitis. • Asymptomatic patients with isolated, mild elevation of either the unconjugated bilirubin or the Gamma-glutamyltransferase value usually do not have liver disease and generally do not require extensive evaluation.

12. The commonly used liver function tests (LFTs) primarily assess liver injury rather than hepatic function. Indeed, these blood tests may reflect problems arising outside the liver: • Hemolysis. • Bone diseases.

13. Liver Function Tests are not always testes of liver function.

14. Abnormal LFTs often, but not always, indicate that something is wrong with the liver, and they can provide clues to the nature of the problem. However, normal LFTs do not always mean that the liver is normal. Patients with cirrhosis and bleeding esophageal varices can have normal LFTs.

15. Markers of Hepatocellular Injury The most commonly used markers of hepatocyte injury are (AST) and (ALT).

16. Elevated ALT or AST in symptomatic patients: • A Autoimmune hepatitis • B Hepatitis B • C Hepatitis C • D Drug or toxins • E Ethanol • F Fatty liver • G Growths (i.e., tumors) • H Hemodynamic disorder (congestive heart failure) • I Iron (hemochromatosis), copper (Wilson's disease) or Alpha,-antitrypsin deficiency • M Muscle injury

17. In hepatitis C, liver cell death occurs by apoptosis (programmed cell death) as well as by necrosis. Hepatocytes dying by apoptosis presumably synthesize less AST and ALT as they wither away. This probably explains why at least one third of patients infected with hepatitis C virus have persistently normal serum ALT levels despite the presence of inflammation on liver biopsy.

18. Various liver diseases are associated with typical ranges of AST and ALT levels. ALT levels often rise to several thousand units per liter in patients with acute viral hepatitis. The highest ALT levels--often more than 10,000 U per L--are usually found in patients with acute toxic injury subsequent to, for example, acetaminophen overdose or acute ischemic insult to the liver. AST and ALT levels usually fall rapidly after an acute insult.

19. AST and ALT lack some sensitivity in detecting chronic liver injury. Patients with cirrhosis often have normal or only slightly elevated serum AST and ALT levels. • AST and ALT also lack some specificity as markers of hepatocellular injury. • Elevated levels are found in: • - Sever muscular excertion. • - Polymyositis. • - Hypothyrodism.

20. Rare individuals have chronically elevated AST levels because of a defect in clearance of the enzyme from the circulation.

21. The elevated AST/ALT ratio in alcoholic liver disease results in part from the depletion of vitamin B6 (pyridoxine) in chronic alcoholics. ALT and AST both use pyridoxine as a coenzyme, but the synthesis of ALT is more strongly inhibited by pyridoxine deficiency than is the synthesis of AST. Alcohol also causes mitochondrial injury, which releases the mitochondrial isoenzyme of AST, which explain increase AST/ALT ratio in cirrhosis.

22. Markers of Cholestasis • Cholestasis (lack of bile flow) results from: • Blockage of bile ducts: AP and (GGT) rise to several times the normal level rise to several times the normal level, several days of bile duct obstruction or intrahepatic cholestasis. • Disease that impairs bile formation in the liver itself (diffuse infiltrative diseases of the liver such as infiltrating tumors and fungal infections): AP and (GGT) rise to greater than 1,000 U per L, or more than six times the normal value.

23. Persistently elevated liver AP values in Asymptomatic patients Especially women Primary biliary cirrhosis AMA

24. Common bile duct stone: • Condition can simulate acute hepatitis • AST and ALT become elevated immediately up to 500U/L on the first hour. • Elevation of AP and GGT is delayed several days after. • Isolated elevation of GGT level: • This situation may be induced by alcohol and aromatic medications, usually with no actual liver disease.

25. Isolated elevation of AP level (asymptomatic patient with normal GGT level) • Consider bone growth or injury. • Primary biliary cirrhosis. • AP level rises in late pregnancy.

26. Indicators of How Well the Liver Function Bilirubin Albumin Prothrombin time Blood Ammonia

27. Bilirubin • The secretion of conjugated bilirubin into bile is very rapid in comparison with the conjugation step, healthy persons have almost no detectable conjugated bilirubin in their blood. • The serum conjugated bilirubin level does not become elevated until the liver has lost at least one half of its excretory capacity.

28. The delta-bilirubin phenomenon: • When a patient has prolonged, severe biliary obstruction followed by the restoration of bile flow, the serum bilirubin level often declines rapidly for several days and then slowly returns to normal over a period of weeks. • Isolated elevation of unconjugated bilirubin level: • - Consider Gilbert syndrome. • - Hemolysis.

29. Albumin • Although the serum albumin level can serve as an index of liver syntheticcapacity, several factors make albumin concentrations difficult to interpret: • The liver can synthesize. Albumin at twice the healthy basal rate and thus partially compensate for decreased synthetic capacity or increased albumin losses.

30. Albumin has a plasma half-life of three weeks; therefore, serum albumin concentrations change slowly in response to alterations in synthesis. • Two thirds of the amount of body albumin is located in the extravascular, extracellular space, changes in distribution can alter the serum concentration.

31. Patients with Low serum albumin No other concentrations FT abnormalities • Proteinuria • Acute inflammatory states: burns, trauma and sepsis. • Chronic inflammatory states: active rheumatic disorders. • End-stage malnutrition. • Pregnancy.

32. Prothrombin time • Prothrombin time (PT) does not become abnormal until more than 80 percent of liver synthetic capacity is lost. • Abnormal PT prolongation may be a sign of serious liver dysfunction. • Because factor VII has a short half-life of only about six hours, it is sensitive to rapid changes in liver synthetic function. Thus, PT is very useful for following liver function in patients with acute liver failure.

33. An elevated PT can result from a vitamin K deficiency. • A trial of vitamin K injections (e.g., 5 mg per day administered subcutaneously for three days). The PT should improve within a few days.

34. Blood Ammonia • Measurement of the blood ammonia concentration is not always useful in patients with known or suspected hepatic encephalopathy: • Ammonia concentrations are much higher in the brain than in the blood and therefore do not correlate well. • Ammonia is not the only waste product responsible for encephalopathy.

35. Blood ammonia levels are best measured in arterial blood because venous concentrations can be elevated as a result of muscle metabolism of amino acids. • Blood ammonia concentrations are most useful in evaluating patients with stupor or coma of unknown origin. • It is not necessary to evaluate blood ammonia levels routinely in patients with known chronic liver disease who are responding to therapy as expected.

36. Markers of Detoxication • Breath tests e.g. C14 aminopyrine, permits quantitative measurement of drug metabolism, it consists of giving C14 labelled aminopyrine by mouth. The labeled methyle groups undergo demthylation after which they are converted to Co2. Accordingly, expired Co2 becomes a measure of metabolic conversion of the drug, and of the hepatic microsomal mass. • Aminopyrine be potentially toxic so: • * Caffiene clearance test ( 3.5 mg/kg max. 200 mg ) • Lidocaine clearance (1.0 mg /kg), measurement of MEGX.

37. Lodacaine: • It is an aminoethylamine that undergo de-ethylation in the liver by cytochrome p450, the major metabolite is monoethylglycine xylidide (ME GX). • Its clearance is decreased in direct relation to hepatic injury and provides prognostic information regarding hepatic metabolic function. • Lidocaine l mg/kg I.V. over 60 sec. • Serum samples at base line and 15 min. • Assess MEGX by automated fluorescence polarization immunoassay. • Used to predict hepatic function in liver donors and in candidates for liver transplantation.

38. Galactose clearance: • For cytosol galactokinase. 99Tc-labelled sialoglycoprotein analogue. • For sinusoidal membrane receptor.

39. Tumour Markers • AFP • AFP fraction • CEA • Serum Ferritin • Des gamma carboxyprothrombin

40. Grading Liver Function by Child-Turcotte Class • This grading system can be used to: • Predict overall life expectancy. • Surgical mortality in patients with cirrhosis and other liver diseases. • Transplantation.

41. The presence of cirrhosis by itself is not an indication for liver transplantation, and transplantation is rarely performed in patients who fall into Child class A. For example, the 10-year survival rate is as high as 80 percent in patients with hepatitis C and cirrhosis who have Child class A liver function and no variceal bleeding. However, once patients with any type of liver disease fall into the Child-Turcotte class B or class C category, survival is significantly reduced and transplantation should be considered.

42. Liver Function Using the Child-Turcotte Class as Modified by Pugh.

43. Patients with a score of 5 to 6 were given a grade A and were considered to be good candidates for sclerotherapy. A score from 7 to 9 was classifid as grade B and of moderate surgical risk . Patients with a score of 10 to 15 were classified as grade C and were considered poor surgical candidates. The Child –Pugh grade has been equated with survival rates for patients with liver disease. Grade C patients have an overall mortality near 80% at 5 years.

44. The parameters described in the Child-Pugh system are useful to monitor patients over time to assess the severity and progression of cirrhosis. In contrast, liver enzymes such as ALT/AST and ALP are variable and to not correlate with the degree of hepatic dysfunction in patients with cirrhosis. A falling albumin and an increasing bilirubin and PT indicate progression of cirrhosis.

45. Liver transplantation: The presence of cirrhosis by itself is not an indication for liver transplantation, and transplantation is rarely performed in patients who fall into Child class A. For example, the 10-year survival rate is as high as 80 percent in patients with hepatitis C and cirrhosis who have Child class A liver function and no variceal bleeding. However, once patients with any type of liver disease fall into the Child-Turcotte class B or class C category, survival is significantly reduced and transplantation should be considered.

46. Thank You