Transcript Liver Function profile (LFT)

Lab (2):
Liver Function profile (LFT)
Lecturer. Nouf Alshareef
KAU-Faculty of Science- Biochemistry department
Clinical biochemistry lab (Bioc 416)
2012
• Profile : is group of tests specific for one organ
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:





Viruses (heptites A,B,C,D,G)
Cirrhosis
Inflammation
Jaundice
Fatty liver
Liver diseases
Liver Function Test (LFT) profile
Integrity of liver cells
Execratory function
Synthetic function
Clinical Lab tests
Liver enzymes
AST, ALT, GGT, ALP
Bilirubin, ALP
Proteins
TP, Alb, A/G ratio
Liver enzymes
ALT (alanine amino transferase) or
i (Serum Glutamate Pyruvate Transaminase)
SGPT
v by liver cells.
• Produced
• High serum ALT due to:
 Livere cells damage due to inflammation, virus infection or cell
deathr(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)
• Synthesized by : liver, cardiac muscle and skeletal muscles
• Less sensitive that ALT
• 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
ALP (alkaline phosphatase)
• It is related to bile duct.
• 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.
• 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)
• Produced by liver, kidney and pancreas
• Elevated in: toxins, alcohol
• 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.
• 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
•
•
•
•
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