Liver Function Tests Flashcards
Cholestasis
bile is not flowing
Where are transferases found?
AST/ALTFound in hepatocyte. AST specifically is also found in muscle.
Where are alkaline phosphatases found?
The biliary ductal system
Alkaline phosphatase also found in bone, ovary, intestine pancreas and kidney
GGTP more specific for biliary tract
Where is bilirubin found?
The biliary ductal system
Alkaline phosphatase also found in bone, ovary, intestine pancreas and kidney
GGTP more specific for biliary tract
Where is gamma glutamyl transpeptidase
The biliary ductal system
Alkaline phosphatase also found in bone, ovary, intestine pancreas and kidney
GGTP more specific for biliary tract
Where is albumin found
it is ONLY produced in the liver. so, the hepatocyte, hands down.
What is Promthrombin time (INR)?
Measure of hepatic synthetic function through blood clotting. Albumin clotting factor proteins are synthesized exclusively in the liver.
Where is amylase/lipase found? (Even though they are not liver function tests)
The pancreas. Amylase also found in saliva and small intestine. Lipase more specific to the pancreas
Normal values of: AST/ALT : •Bilirubin : Total: , Direct: •Alk. P’tase : •Albumin : •INR: •Amylase : •Lipase :
AST/ALT : 0-40 units/dL Bilirubin : Total: 0.3-1.2 mg/dL, Direct: 0-0.3 Alk. P’tase : 36-92 units/dL Albumin : 3.5-5.5 grams/dL INR: 1.0 Amylase : 0-130 units/L Lipase : 0-95 units/L
SGOT/SGPT = (note that these SGOT/SGPT names should not be seen anymore.)
AST/ALT
What are AST/ALT? What does elevation of these guys mean?
AST/ALT are tranaminases. Elevation of these guys indicates that there is damage to the hepatocytes resulting in leakage of the enzymes into the serum. Think about the heart and troponins and MB-creatine kinase
Why is the normal AST/ALT 0-40 IU’s/dL
This is the case, as normal ranges could be aorund 40, but it may never be 0 since hepatocyte are naturally always dying (natural apoptosis), so you can expect to see some AST/ALT anyway. Note that you measure this stuff by drawing blood, and mixing it with the enzymes used to convert it, giving it a color. You measure the amount of color present.
What is AST? AST/ALT, how do you measure what is normal or abnormal?
Aspartate transaminase. It catalyzes the exchange of an amino group and a alpha keto group. In terms of measuring ahwat is normal and abnormal, you take the base value (usually the 0-40 standard) and see it is multiplied (2x, 5x, 10x, etc). Watch over time. 1000/900 is sky high. 75/85 is low, but it is still above standard and can be just as serious 0….o
What AST/ALT value do patients with chronic liver disease (viral, alcohol, metabolic, NASH, autoimmune) usually present with?
50-70 IU/dl for YEARS. The number is still considered low, but the amount of time is high. NASH is connected to metabolic syndrome…hypertension, hyperlipidemia. With this this high fat diet and with this fat infiltration in the liver, some of the patients get hepatitis…hence, non-alcoholic, steatol, hepatitis (NASH)
Generally ALT is higher than AST. Why? And why is this relationship important?
Liver cells are richer in ALT. If you ever see AST higher than ALT, suspect alcholic related liver disease. Think L for liver. So liver should have more ALT. Going back to AST being higher than ALT in alcoholoics, the reason likely has to deal with fact that ALT has pyridocal 5’phosphate as a cofactor and if deficient, as in alcoholism, the enzyme level is now low.
What are extraheptic reasons for cholestasis?
tumor, stone, stricture. All these can obstruct bile flow.
What are intrahepatic reasons for cholestasis?
Virus, drug, deficiency of an enzyme.
Mentality when thinking of bilirubin issues:
Where is the bilirubin being held up? Find the obstruction = find the diagnosis.
Do not fractionate bilirubin (as in, do not split total bilirubin into direct and indirect values) if:
You bilirubin lab value is greater than 5. won’t tell you anything. It is only useful if is it just above normal but below 5 or 6.
Where do you see bilirubin in a patient, if patient is being bilirubin issue? Which disappears first?
Sclera of eye + yellow color in skin (on lighter skin colors). Note that the skin’s color will normalize first when the patient is getting better. Reason is because bilirubin is very soluble in ELASTIN pigment, which is in the eye. They are still getting better, but the eyes will be the last to show it.
Gilbert’s syndrome
deficiency of glucuronyl transferase. Therefore an elevation of unconjugated (indirect) bilirubin is noted in the serum
Dubin-Johnson Syndrome
involve a deficiency of multiple drug-resistance protein 2 (MRP2) preventing the transfer of conjugated bilirubin (direct) into bile canaliculi.
How to tell difference between Gilbert’s syndrome and Dubin-Johnson Syndrome
Dubin Johnson: Direct (has already been conjugated). but Gilbert’s: Indirect
What is the significance of increased alkaline phosphatase? What is the problem with using this measuring technique?
Increased levels in the serum due to increased production in the bile canalicular cells in the disease state (as in disease is causing an increases in the amount of alkaline phosphates normally produced.) Issue: It is not just found in hepatocytes, but also found in BONE (increased in growing kids due to normal bone growth!!!), ovary, WBC’s
How do you overcome fact that alk phos is found in places besides the liver?
Use Gamma glutamyl transpeptidase (GGTP). Very hepatocyte-billiary specific. Proves that the issue is billiary related. IN other words, if alk phos and GGTP are both high, it is liver billiary issue. If alk phos is high but GGTP is normal, it cannot be a liver issue. these 2 are coupled when diagnosing.
Classic pattern of hepatocellular damage will have
Bilirubin:
Alk phos:
Transaminases:
Bilirubin: low
Alk phos: low
Transaminases: high
Classic pattern of cholestatic damage will have
Bilirubin:
Alk phos:
Transaminases:
Bilirubin: high
Alk phos: high
Transaminases: low
AST/ALK = 65/75
Bilirubin = 2.5
Alk phos = 180
What kind of patient would present like this?
One who consumes alcohol for years…end stage cirrhosis, drug reaction
AST/ALK = 85/96
Bilirubin = 1.0
Alk phos = 120
What kind of patient would present like this?
drug reaction, OH, NASH
what do you do first when trying to treat a patient with ambiguous LFT’s?
Imaging study. check the ducts. check drugs patient is taking too.
How and why would you attempt to use albumin as a measure of hepatic function?
Albumin is only made in the liver. period. So if albumin is low, it could be because of malnutrition, malabsoprtion, renal disease. Essentially, low albumin is associated with CHRONIC liver disease, and it also suggests failure of hepatocyte synthetic ability. Could even signify loss of hepatocytes (cirrhosis)
Cirrhosis
Loss of hepatocytes.
What is the point of prothrombin time (INR)?
INR measures clotting factor functions of V, VII, IX, X in the extrsinsic clotting cascade. These guys are ALL made in the liver. VII just so happens to have a really short half-life, but you need it in order to clot. If you notice a lengthening prothrombin time, this suggests a chronic liver disease or acute hepatic failure.
hepatitis
classic injury to liver presentation. expect high ALT/AST
Job of lipase, and what does it mean?
specific for pancreatitis.
Job of amylase, and what does it mean?
specific for pancreatitis
