Blood Chemistry 1 PDF - Liver Function Tests

CLIN. PRACT. IN BIOCHEMISTRY Blood Chemistry 1 CLS 488 Liver Function Tests (LFT)  Liver Function The liver is the largest internal organ of the human body. It is a functionally complex organ that plays a critical biochemica...

CLIN. PRACT. IN BIOCHEMISTRY Blood Chemistry 1 CLS 488 Liver Function Tests (LFT)  Liver Function The liver is the largest internal organ of the human body. It is a functionally complex organ that plays a critical biochemical role in the metabolism, digestion, detoxification, and elimination of substances from the body. The liver is involved in a number of excretory, synthetic, and metabolic functions, all of which are essential to life. Liver functions: Synthesizes glycogen from glucose Makes plasma proteins (albumin, lipoproteins, coagulation proteins) Forms cholesterol and degrades it into bile acids, which emulsifies fats for absorption Stores iron, glycogen, vitamins and other substances Destroys old blood cells and recycles components of hemoglobin  Liver Function Tests (LFT): A Liver Health Panel, also known as Liver (hepatic) Function Tests or LFT, is used to detect liver damage or disease. These include: Alkaline phosphatase (ALP). Alanine Aminotransferase (ALT). Aspartate Aminotransferase (AST). Gamma Glutamyl Transferase (GGT). Total Bilirubin (BILT2). Total protein (TP). Albumin. Globulin. Ammonia (NH3). Liver enzymes play an important role in the assessment of liver function because injury to the liver resulting cytolysis or necrosis will cause the release of enzymes into circulation. that is why the levels of these enzymes in the blood are considered good indicators of liver cell damage. ALT is found mainly in the liver (lesser amounts in skeletal muscle and kidney), whereas AST is widely distributed in equal amounts in the heart, skeletal muscle, and liver, making ALT a more “liver-specific” marker than AST. The AST, for instance, will rise after a heart attack or injured kidney. GGT and ALP are said to be more specific for evaluating biliary disease since they are made in bile duct cells. Chronic alcohol consumption can increase GGT levels, making it a useful marker for alcohol-related liver damage. In liver disease caused by excess alcohol ingestion, the AST tends to exceed the ALT, while the reverse is true for viral hepatitis.  Phosphatases Alkaline phosphatase (ALP) Type: Enzyme Location: Mainly in Liver and Bones also found in other organs, such as placenta, and intestine. For this reason, the GGT is utilized as a supplementary test to be sure that the elevation of alkaline phosphatase is indeed coming from the liver or the biliary tract. Function: Hydrolyses phosphate at high pH in vitro. helps break down proteins. Disease associated: Increased in: Liver, Bone and Malignant diseases, Gallstone, tumor blocking the common bile duct, alcoholic liver disease, drug-induced hepatitis, blocking the flow of bile in smaller bile channels within the liver. Decreased in: Anaemia, scurvy Method: Colorimetric: A red colored product is formed reaction between phenol and 4 aminophenazone in the presence of oxidizing agent potassium ferricyanide. Note: ALP increases during bone growth and in pregnant women. Specimen type :Plasma  Gamma Glutamyl Transferase (GGT) Type: Enzyme Location: It founds in high concentrations in the kidney, liver, pancreas, intestine, and prostate but not in bone. Function: Catalyzes the transfer of gamma Glutamyl group from one peptide to another or to an amino acid. Disease associated: Increased in: 1. Cholestatic Liver Diseases. 2. Acute Hepatitis. 3. Chronic alcohol abuse 4. Cirrhosis of the Liver. 5. Cancer of the Liver. Note: Often used to monitor patients recovering from hepatitis and cirrhosis This enzyme level is elevated in case of liver disorders. In contrast to the alkaline phosphatase, the GGT tends not to be elevated in diseases of bone, placenta, or intestine. GGT is highly sensitive to alcohol consumption. It is one of the most commonly used markers to assess alcohol-related liver damage. Even moderate alcohol consumption can lead to elevated GGT levels, and chronic heavy drinking often results in significantly increased GGT values.  Aminotransferases The two most common aminotranferases measured in the clinical laboratory are AST (formerly referred to as serum glutamic-oxaloacetic transaminase [SGOT]) and ALT (formerly referred to as serum glutamic-pyruvic transaminase [SGPT]). Aspartate Aminotransferase (AST) Type: Enzyme Location: Liver, Heart and Skeletal Muscles Function: Catalyzes the transformation of amino acids from ketoglutrate to Aspartate to form Oxaloacetate. Disease associated: Increased in: liver disease, and in heart attacks For AST - up to 40 unit/L  Alanine Aminotransferase (ALT) Type: Enzyme Location: Mainly in Liver Function: Catalyzes the transformation of amino acids from ketoglutrate to Alanine to form Pyruvate. Disease associated: Increased in: In Liver diseases, increases up to 10x in cirrhosis, infections or tumors and up to 100x in viral or toxic hepatitis For ALT – up to 35 unit/L Method: AST&ALT Activity of transaminases is determined by measuring the colour of the hydrazone which is formed by the reaction of pyruvate with 2,4 di -nitrophenyl hydrazine Specimen type : Plasma  Bilirubin (Conjugated or Direct) Type: Conjugated Bilirubin is a Water soluble form of Bilirubin. Location: Conjugation with Glucuronic acid takes place in the Liver by Uridyl-Diphosphate Glucuronyl Transferase (UDGT) and passes into the Bile system. Function: Conjugated Bilirubin is broken down in the gut to form stercoblinogen and accounts for the normal color of faeces Disease associated: Increased in: Choletasis (Obstruction of Bile Flow) Method: Colorimetric reaction by coupling of direct Bilirubin with diazotized sulphanilic acid to form an Azo dye (Jendrassik)Organic Compound (conjugated). Normal values- Total bilirubin- upto 1.0 mg/dl Direct bilirubin - upto 0.25 mg/dl Indirect bilirubin - 0.2-0.8 mg/dl *Elevation of unconjugated bilirubin is due to hemolysis or genetic disease..  Total Bilirubin Type: Organic Compound (conjugated and unconjugated forms). Location: Liver Function: Bilirubin is a Bile pigment formed from the breakdown of Heme group of hemeprotiens (e.g. hemoglobin). Disease Increased in: In Acute hemolysis and Liver diseases. associated: Increase levels of Bilirubin may cause Jaundice. Method: Malloy and Evelyn method Bilirubin reacts with diazotized sulphanilic acid to produce azobilirubin which is purple in color. If an accelerator such as ethanol or caffeine – benzoate is added to the reaction mixture, the unconjugated bilirubin will also form azobilirubin, so that total (both conjugated and unconjugated) plasma bilirubin can be determined. Intensity of color is directly proportional to the amount of bilirubin in serum. Normal Conjugated bilirubin Unconjugated bilirubin 12 Haemolytic Jaundice Conjugated bilirubin Unconjugated bilirubin 13 Intra/Extra Hepatic Obstruction Conjugated bilirubin Unconjugated bilirubin 14 Liver  Albumin (ALB). Type: Protein Location: Synthesized in the Liver. Function: 1. Carries ions and molecules (e.g. Bili & Ca). 2. Maintains oncotic pressure. 3. Regulates plasma volume. Disease Increased in: associated: In Dehydration Decreased in: In Oedema, Nephrotic syndrome and Burns Method: Bromo-Cresol Green (BCG) at pH 4.1 Albumin binds quantitatively with bromocresol green at pH 4.15 resulting in the formation of a green colour which can be measured at 630nm/red filter. Reference range - Serum albumin - 3.5-5.0 g/dl Note: Low levels also affect binding site availability and can give falsely low levels of total Calcium (Ca).  Total protein Type: The sum of all proteins and globulins Location: Most proteins are synthesized in the Liver and released into biological fluids Function: It measures the sum of circulating proteins: Albumin, Alpha-1, Alpha-2, Beta and Gamma Globulins. Albumin must be measured at the same time to distinguish any increase or decrease in fractions Disease associated: Increased in: Multiple Myeloma and Immunoglobulin Disorders. Decreased in: Liver and Kidney Diseases. Method: Colorimetric (Biuret Method) in which protein forms a violet/purple colored complex with copper ions in an alkaline medium proportional to its concentration  Ammonia (NH3) Type: Organic Molecule. Location: Liver Function: Toxic waste of degradation of amino acids. Disease associated: Increased in: Sever Liver diseases such as Cirrhosis, Hepatitis. Method: Color-Enzymatic oxidizes; NADPH (reduced form) to NADP+ (oxidized form). Note: NADP= Nicotinamide-Adenine Dinucleotide Phosphate The table below demonstrates the typical LFT patterns associated with acute hepatocellular damage, chronic hepatocellular damage and cholestasis. A single arrow (↑) refers to a mild impairment and a double arrow (↑↑) refers to Moderate elevation and (↑↑↑) severe impairment. Acute hepatocellular Obstructive damage Jaundice ALT ↑↑↑ ↑ AST ↑↑↑ ↑ ALP Normal or ↑ ↑↑↑ GGT Normal or ↑ ↑↑↑ Conj Bilirubin ↑ or ↑↑ ↑↑↑ Unconj Bilirubin ↑ or ↑↑ ↑  Renal Function Tests (RFT): 1. Albumin (ALB). 2. Creatinine (CRE). 3. Urea.  Albumin (ALB). Type: Protein Location: Synthesized in the Liver. Function: 1. Carries ions and molecules (e.g. Bili & Ca). 2. Maintains oncotic pressure. 3. Regulates plasma volume. Disease Increased in: associated: In Dehydration Decreased in: In Oedema, Nephrotic syndrome and Burns Method: Bromo-Cresol Green (BCG) at pH 4.1 Albumin binds quantitatively with bromocresol green at pH 4.15 resulting in the formation of a green colour which can be measured at 630nm/red filter. Reference range - Serum albumin - 3.5-5.0 g/dl Note: Low levels also affect binding site availability and can give falsely low levels of total Calcium (Ca).  Creatinine (CRE) Type: Organic Compound. It is a waste product of normal muscle metabolism Location: Muscle tissues and then released into blood Function: Plasma Creatinine is mostly derived from breakdown of Creatine and then excreted by kidney into urine. Therefore, it uses to assess the kidney function. Disease Increased in: associated: Kidney diseases. Method: Colorimetric: Jaffe’s method Creatinine reacts with saturated solution of picric acid in alkaline medium to form a red colour compound known as creatinine picrate. The color change that occurred was directly proportional to the concentration of creatinine Note: Normal levels: 0.6 to 1.2 mg / dl  Urea Type: Organic Compound of breakdown of amino acids in the Liver Location: Plasma and Urine Function: Urea is used as a marker of renal function and as an indication of reduced blood flow. Disease Increased in: associated: 1. Renal Failure. 2. High Protein Diet (Increased catabolism due to Starvation or Tissue damage may cause moderate elevation). 3. Dehydration. 4. Heart Failure Decreased in: 1. Advanced Liver Disease. 2. Hemodialysis.  Cardiac Function Cardiac Enzymes The enzymes currently in clinical use to detect myocardial infarction are CK and its isoenzyme CK-MB. Cardiac Proteins The preferred biomarkers for assessment of myocardial necrosis are the cardiac troponins. Troponin is a complex of three proteins that bind to the thin filament (actin) of cardiac muscle. The three proteins of the troponin complex are troponin T (TnT), troponin I (TnI),and troponin C (TnC). Troponin I (TnI) and Troponin T (TnT): The major function of troponins is to bind calcium and regulate muscle contraction. Elevation of one of the cardiac troponins, which are almost identical in their clinical usage, is more sensitive and specific for myocardial infarction than CKMB. Concentrations rise within 4 - 12 hours of commencement of cardiac pain and remain elevated for 7 days in the case of TnI or 10 days for TnT. Reference range :