Liver Function profile LFT Enzymes Khadija Balubaid KAUFaculty
Liver Function profile (LFT) Enzymes Khadija Balubaid KAU-Faculty of Science- Biochemistry department Clinical biochemistry lab (BIOC 416) 2013
Liver • Liver is an important organ in human body • Synthesis of proteins, glycogen storage, drug metabolism and detoxification process • Many diseases can affect liver functions as: v v v Viruses (heptites A, B, C, D, G) Cirrhosis Inflammation Jaundice Fatty liver
Liver profile § Profile : is group of tests specific for one organ § Liver function tests (LFTs or LFs), are groups of clinical biochemistry laboratory blood (serum or plasma) or urine assays designed to give information about the state of a patient's liver § These tests can be used to Ø detect the presence of liver disease Ø distinguish among different types of liver disorders Ø Gauge the extent of known liver damage, Ø follow the response to treatment.
Liver enzymes ALT (alanine amino transferase) or SGPT (Serum Glutamate Pyruvate Transaminase) • Produced by liver cells. • ALT found primarily in liver. • Normal : 7 – 41 U/L • Upto 300 U/L – nonspecific , any type of liver disorder(CLD…cirrhosis /malignancy) • >1000 U/L – extensive hepatocellular damage ( viral hepatitis, ischemic liver injury , toxin /drug induced liver injury )
• High serum ALT due to: Ø Liver cells damage due to inflammation, virus infection or cell death (why? ) when liver cells damaged ALT enzyme leaks to blood stream leads to rise its level in serum. Ø Some medication may also elevate serum ALT, because some drugs cause liver damage leads to rise ALT level. • ALT is the most sensitive marker for liver cell damage; since it is only synthesized by liver cells other enzymes may be also synthesized by other organs.
AST (Aspartate amino transferase) or SGOT (Serum Glutamate Oxaloacetate Transaminase) § Less sensitive that ALT § Synthesized by : liver, cardiac muscle, skeletal muscles, kidneys, brain, pancreas, lungs, leucocytes and RBC § Normal – 12 – 38 U/L § AST – liver , cardiac muscles, skeletal muscle, kidneys, brain, pancreas, lungs, leucocytes, RBC in decreasing order. § 2 Iso enzymes- cytoplasmic, mitochondrial § Mild degree of tissue injury – cytoplasmic form in serum § Severe injury – mitochondrial type in serum
§ High serum AST due to: § Muscle damage, myocardial infarction (heart attack) and in chronic liver disease. To confirm that high AST is due to heart or muscle injury; other enzyme (creatinine kinase CK) which is specific for heart, is also tested. § Because it is less sensitive the ration ALT/AST is calculated § ALT: < 35 U/L, AST: <40 U/L § elevated ALT, AST : acute hepatitis (viral or toxic ), chronic hepatitis and cirrhosis, biliary obstruction
ALP (alkaline phosphatase) • It is related to bile duct. • ALP normal level: 30 -130 U/L • It is not specific for bile because it is synthesized also by bone and placenta (isoenzymes) • High serum ALP may be due to: Ø bile duct damage (inflammation, cirrhosis or obstruction) Ø In alcohol hepatitis. Ø Hepatocellular carcinoma
§ Normal physiological elevation : Ø During pregnancy Ø During child growth § To assess the etiology of ALP elevation, GGT and bilirubin levels are also measured.
GGT (Gamma Glutamic Transpeptidase) § § Used in body for syn of glutathione 11 iso enzymes Normal : 9 – 58 U/L Produced by liver, kidney and pancreas, intestinal cells, and prostate § Elevated in: toxins, alcoholism, obstructive Jaundice, and neoplasm of liver § Slightly high normally in males prostate § To detect alcohol abuse § Rised even when other LFT are normal in alcohalics. § GGT falls rapidly within few days after abstinence. § Used To confirm hepatic etiology of ALP elevation
General indications In general, every enzyme can gives you specific indication: Enzymes Indications Conformational procedures ALT Hepatitis. may be due to ( virus, medication, toxin) Serology (for virus) Biopsy, ultrasound (liver size) AST Not specific. AST/ALT ratio, May be due to ( muscle disease, heart disease, liver CK to confirm heart disease) disease ALP • Bile problems (stone or bilary duct obstruction) GGT to confirm liver • Liver disease Gallbladder • Normal physiological elevation ( child, pregnancy) ultrasound GGT Liver toxin, alcohol, cirohsis
Experiment: Measuring serum AST level • Principle: • L-aspartate + a oxoglutarate AST Oxaloacetate + NADH + H+ MDH L-glutamate + oxaloacetate L-malate + NAD + • The rate of NADH oxidation is directly related to AST activity which measured photometrically.
Notes: • Samples: Unhemolyzed serum or plasma collected in heparin or EDTA tube. (why? ) • Stability of AST in serum: 2 days at 20 -25 o. C or 4 days at 2 -8 o. C
Kit components • Reagent 1: mixture of: buffer (p. H 7. 5) + substrate (L-aspartate) • Reagent 2: mixture of: enzyme (MDH) + coenzyme (NADH)
Procedure • Prepare working reagent: by mixing reagent 1 and 2 together • Zero adjust the spectrophotometer with air or dis. H 2 O • Prepare the reaction as the following: Sample tube • • Working reagent 1 ml Sample (serum) 100 ml Mix After 30 sec. read the absorbance at 340 nm. (R 1) Repeat the reading after 1 min and 2 min (R 2, R 3) Calculate the mean absorbance mean = R 1+R 2+R 3/ 3 or (R 2 -R 1)+(R 3 -R 2)/2
Calculations: AST catalytic conc. U/L = mean A X factor * factor = 1946 Reference value “ normal rang”: Men Women 25 o. C 18 U/L 15 U/L
Interfering factors • Therapeutic heparin increase AST • Hemolysed blood increase AST • Many drugs falsely increase or decrease AST
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