Liver Blood Test

موضوع: Liver Blood Test الجمعة يوليو 22, 2011 3:41 pm

Introduction to liver blood test

An
initial step in detecting liver damage is a simple blood test to
determine the presence of certain liver enzymes in the blood. Under
normal circumstances, these enzymes reside within the cells of the
liver. But when the liver is injured for any reason, these enzymes are
spilled into the blood stream. Enzymes are proteins that are present
throughout the body, each with a unique function. Enzymes help to speed
up (catalyze) routine and necessary chemical reactions in the body.

Among
the most sensitive and widely used of these liver enzymes are the
aminotransferases. They include aspartate aminotransferase (AST or SGOT)
and alanine aminotransferase (ALT or SGPT). These enzymes are normally
contained within liver cells. If the liver is injured, the liver cells
spill the enzymes into blood, raising the enzyme levels in the blood and
signaling the liver damage.

What are the aminotransferases?

The
aminotransferases catalyze chemical reactions in the cells in which an
amino group (amino acids are building blocks of proteins) is transferred
from a donor molecule to a recipient molecule. Hence, the names
"aminotransferases."

Medical terms can sometimes be confusing, as is the case with these enzymes.
Another name for aminotransferase is transaminase.

The enzyme aspartate aminotransferase (AST) is also known as serum glutamic oxaloacetic transaminase (SGOT); and

alanine aminotransferase (ALT) is also known as serum glutamic pyruvic transaminase (SGPT).

To put matters briefly, AST = SGOT and ALT = SGPT.

Normally, where are the aminotransferases?

AST
(SGOT) is normally found in a diversity of tissues including liver,
heart, muscle, kidney, and brain. It is released into serum when any one
of these tissues is damaged. For example, its level in serum rises with
heart attacks and with muscle disorders. It is therefore, not a highly
specific indicator of liver injury.

ALT (SGPT) is, by contrast,
normally found largely in the liver. This is not to say that it is
exclusively located in liver, but that is where it is most concentrated.
It is released into the bloodstream as the result of liver injury. It
therefore serves as a fairly specific indicator of liver status.

What are normal levels of AST and ALT?

The normal range of values for AST (SGOT) is from 5 to 40 units per liter of serum (the liquid part of the blood).

The normal range of values for ALT (SGPT) is from 7 to 56 units per liter of serum.

What do elevated AST and ALT mean?

AST
(SGOT) and ALT (SGPT) are sensitive indicators of liver damage or
injury from different types of disease. But it must be emphasized that
higher-than-normal levels of these liver enzymes should not be
automatically equated with liver disease. They may mean liver problems
or they may not. For example, elevations of these enzymes can occur with
muscle damage. The interpretation of elevated AST and ALT levels
depends upon the entire clinical evaluation of a patient, and so it is
best done by doctors experienced in evaluating liver disease.

The
precise levels of these enzymes do not correlate well with the extent
of liver damage or the prognosis (outlook). Thus, the exact levels of
AST (SGOT) and ALT (SGPT) cannot be used to determine the degree of
liver disease or predict the future. For example, patients with acute
viral hepatitis A may develop very high AST and ALT levels (sometimes in
the thousands of units/liter range). But most patients with acute viral
hepatitis A recover fully without residual liver disease. For a
contrasting example, patients with chronic hepatitis C infection
typically have only a little elevation in their AST and ALT levels. Some
of these patients may have quietly developed chronic liver disease such
as chronic hepatitis and cirrhosis (advanced scarring of the liver).

It
is, therefore, worth mentioning that these liver enzymes do not give an
indication of the function of the liver. Sometimes they are mistakenly
referred to as “liver function tests” or LFTs, but it is a misnomer
commonly used.

What liver diseases cause abnormal aminotransferase levels?

The
highest levels of AST and ALT are found with disorders that cause the
death of numerous liver cells (extensive hepatic necrosis). This occurs
in such conditions as:
acute viral hepatitis A or B,

pronounced liver damage inflicted by toxins as from an overdose of acetaminophen (brand-name Tylenol), and

prolonged collapse of the circulatory system (shock) when the liver is deprived of fresh blood bringing oxygen and nutrients.

AST
and ALT serum levels in these situations can range anywhere from ten
times the upper limits of normal to thousands of units/liter.

Mild
to moderate elevations of the liver enzymes are commonplace. They are
often unexpectedly encountered on routine blood screening tests in
otherwise healthy individuals. The AST and ALT levels in such cases are
usually between twice the upper limits of normal and several hundred
units/liter.

One of the most common cause of mild to moderate
elevations of these liver enzymes is fatty liver. In the United States,
the most frequent cause of fatty liver is alcohol abuse. Other causes of
fatty liver include diabetes mellitus and obesity. Chronic hepatitis C
is also becoming an important cause of mild to moderate liver enzyme
elevations.

What medications cause abnormal aminotransferase levels?

A host of medications can cause abnormal liver enzymes levels.

Examples include:

Pain relief medications such as:
aspirin,

acetaminophen (Tylenol),

ibuprofen (Advil, Motrin),

naproxen (Naprosyn, Naprelan, Anaprox, Aleve),

diclofenac (Voltaren, Cataflam, Voltaren-XR)), and

phenylbutazone (Butazolidine)

Anti-seizure medications such as:
phenytoin (Dilantin),

valproic acid (Depakote, Depakote ER, Depakene, Depacon),

carbamazepine (Tegretol, Tegretol XR, Equertro), and

phenobarbital

Antibiotics such as:
tetracyclines, [for example, tetracycline (Achromycin)]

sulfonamides,

isoniazid (INH) (Nydrazid, Laniazid)

sulfamethoxazole (Gantanol),

trimethoprim (Trimpex; Proloprim, Primsol)

nitrofurantoin (Macrodantin; Furadantin; Macrobid),

fluconazole (Diflucan ) and some other anti-fungals, etc.

Cholesterol lowering drugs such as:
the statins:

lovastatin (Mevacor, Altocor),

pravastatin (Pravachol),

atorvastatin (Lipitor),

fluvastatin (Lescol),

rosuvastatin (Crestor),

simvastatin (Zocor), and

niacin

Cardiovascular drugs such as:
amiodarone (Cordarone),

hydralazine (Apresoline)

quinidine (Quinaglute, Quinidex), etc.

Other drugs

Anti-depressant drugs of the tricyclic type

With drug-induced liver enzyme abnormalities, the enzymes usually normalize weeks to months after stopping the medications.

What are less common causes of abnormal aminotransferase levels?

Less
common causes of abnormal liver enzymes in the United States include
chronic hepatitis B, hemachromatosis (iron overload), Wilson's disease,
alpha-1-antitrypsin deficiency, celiac sprue, Crohn's disease,
ulcerative colitis, and autoimmune hepatitis. Though not as common as
hepatitis C, hepatitis B can cause chronic liver disease with
persistently abnormal liver enzymes.
Hemachromatosis is a genetic
(inherited) disorder in which there is excessive absorption of dietary
iron leading to accumulation of iron in the liver with resultant
inflammation and scarring of the liver.

Wilson's disease is an
inherited disorder with excessive accumulation of copper in diverse
tissues including the liver and the brain. Copper in liver can lead to
chronic liver inflammation, while copper in brain can cause psychiatric
and motor disturbances.

Alpha-1-antitrypsin deficiency is an
inherited disorder in which the lack of a glycoprotein
(carbohydrate-protein complex) called alpha-1-antitrypsin lead to
chronic lung disease (emphysema) and to liver disease.

Autoimmune
hepatitis results from liver injury brought about by the body's own
antibodies and defense systems attacking the liver.

Celiac sprue
is a small intestinal illness where a patient has allergy to gluten and
develops gas, bloating, diarrhea, and in advanced cases malnutrition.
Patients' with celiac sprue can also develop mildly abnormal ALT and AST
levels.

Crohn's disease and ulcerative colitis are diseases with
chronic inflammation of the intestines. In these patients inflammation
of the liver (hepatitis) or bile ducts (primary sclerosing cholangitis)
also can occur, causing abnormal liver tests.

Rarely, abnormal
liver enzymes can be a sign of cancer in the liver. Cancer arising from
liver cells is called hepatocellular carcinoma or hepatoma. Cancers
spreading to the liver from other organs (such as colon, pancreas,
stomach, etc) are called metastatic malignancies

» اختبارات وظائف الكبد Liver function test
» صورة الدم الكاملة Complete Blood Count
» النسب الطبيعيه لصورة الدم الكامله(complete blood count):
» فحص وظائف الكبد Liver Function Tests
» Alph1-Antitrypsin Test