Transcript Liver Function profile (LFT) Enzymes

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:
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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
 detect the presence of liver disease
 distinguish among different types of liver disorders
 Gauge the extent of known liver damage,
 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 300U/L – nonspecific , any type of liver
disorder(CLD…cirrhosis /malignancy)
• >1000U/L – extensive hepatocellular damage ( viral hepatitis,
ischemic liver injury , toxin /drug induced liver injury )
• High serum ALT due to:
 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.
 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 – 38U/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: < 35U/L,
AST: <40U/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:
 bile duct damage
(inflammation, cirrhosis or obstruction)
 In alcohol hepatitis.
 Hepatocellular carcinoma
 Normal physiological elevation :
 During pregnancy
 During child growth
 To assess the etiology of ALP elevation, GGT and
bilirubin levels are also measured.
GGT (Gamma Glutamic Transpeptidase)
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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)
• Liver disease
• Normal physiological elevation ( child, pregnancy)
GGT
Liver toxin, alcohol, cirohsis
GGT to confirm liver
Gallbladder
ultrasound
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 20-25oC or 4 days at 2-8oC
Kit components
• Reagent 1:
mixture of: buffer (pH 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. H2O
• Prepare the reaction as the following:
Sample
tube
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Working reagent
1 ml
Sample (serum)
100 ml
Mix
After 30 sec. read the absorbance at 340nm. (R1)
Repeat the reading after 1min and 2 min (R2, R3)
Calculate the mean absorbance
mean = R1+R2+R3/ 3 or (R2-R1)+(R3-R2)/2
Calculations:
AST catalytic conc. U/L = mean A X factor
* factor = 1946
Reference value “ normal rang”:
Men
Women
25oC
18 U/L
15 U/L
Interfering factors
• Therapeutic heparin increase AST
• Hemolysed blood increase AST
• Many drugs falsely increase or decrease AST