A Typical Liver Function Test
Result Unit Reference
• AP (Alk Phos) U/L (30 to 120)
• GGT (Gamma GT) U/L (5 to 35)
• LD Lactate Dehydrogenase U/L (100-225)
• AST (Aspartate aminotransferase) U/L (5 to 45)
• ALT (Alanine aminotransferase) U/L (5 to 45)
• Albumin g/L (38-55)
• Clotting Studies (Prothrombin Time) Seconds (11 to 13.5)
• Total Bilirubin - Normal range is 3 - 18 umol/L (0.174 - 1.04mg/dL).
After the result is the laboratory reference range and the units in which the result is expressed eg: U.L
Each laboratory will provide a "reference range" or ‘ normal values' This is the average reading that is deemed a ‘normal' reading for the majority of the population. This will assist the doctor in determining if the patient's results are abnormal.
The normal values for liver function tests will vary between men and women, at different times of the day and will change as you get older. Different laboratories may have slightly differing reference ranges.
Liver Enzymes
ALT - (alanine aminotransferase) - was previously called SGPT is more specific for liver damage. The ALT is an enzyme that is produced in the liver cells (hepatocytes) therefore it is more specific for liver disease than some of the other enzymes . It is generally increased in situations where there is damage to the liver cell membranes. All types of liver inflammation can cause raised ALT. Liver inflammation can be caused by fatty infiltration (see fatty liver) some drugs/medications, alcohol, liver and bile duct disease.
AST - (aspartate aminotransferase) which was previously called SGOT. This is a mitochondrial enzyme that is also present in heart, muscle, kidney and brain therefore it is less specific for liver disease. In many cases of liver inflammation, the ALT and AST activities are elevated roughly in a 1:1 ratio.
AP - (alkaline phosphatase) is elevated in many types of liver disease but also in non-liver related diseases. Alkaline phosphatase is an enzyme, or more precisely a family of related enzymes, that is produced in the bile ducts and sinusoidal membranes of the liver but is also present in many other tissues. An elevation in the level of serum alkaline phosphatase is raised in bile duct blockage from any cause. Therefore raised AP in isolation will generally lead a physician to further investigate this area. Conditions such as Primary Biliary Cirrhosis and Sclerosing Cholangitis will generally show a raised AP. Raised levels may also occur in cirrhosis and liver cancer. Alkaline phosphatase is also produced in bone and blood activity can also be increased in some bone disorders.
GGT - (gamma glutamyl transpeptidase) is often elevated in those who use alcohol or other liver toxic substances to excess. An enzyme produced in many tissues as well as the liver. Like alkaline phosphatase, it may be elevated in the serum of patients with bile duct diseases. Elevations in serum GGT, especially along with elevations in alkaline phosphatase, suggest bile duct disease. Measurement of GGT is an extremely sensitive test, however, and it may be elevated in virtually any liver disease and even sometimes in normal individuals. GGT is also induced by many drugs, including alcohol, therefore often when the AP is normal a raised GGT can often (but not always) indicate alcohol use. Raised GGT can often be seen in cases of fatty liver and also where the patient consumes large amounts of aspartame (artificial sweetener) in diet drinks for example.
Bilirubin is the major breakdown product that results from the destruction of old red blood cells (as well as some other sources). It is removed from the blood by the liver, chemically modified by a process call conjugation, secreted into the bile, passed into the intestine and to some extent reabsorbed from the intestine. It is basically the pigment that gives faeces its brown colour.
Bilirubin concentrations are elevated in the blood either by increased production, decreased uptake by the liver, decreased conjugation, decreased secretion from the liver or blockage of the bile ducts.
In cases of increased production, decreased liver uptake or decreased conjugation, the unconjugated or so-called indirect bilirubin will be primarily elevated.
In cases of decreased secretion from the liver or bile duct obstruction, the conjugated or so-called direct bilirubin will be primarily elevated.
Many different liver diseases, as well as conditions other than liver diseases (e. g. increased production by enhanced red blood cell destruction), can cause the serum bilirubin concentration to be elevated. Most adult acquired liver diseases cause impairment in bilirubin secretion from liver cells that cause the direct bilirubin to be elevated in the blood. In chronic, acquired liver diseases, the serum bilirubin concentration is usually normal until a significant amount of liver damage has occurred and cirrhosis is present. In acute liver disease, the bilirubin is usually increased relative to the severity of the acute process. In bile duct obstruction, or diseases of the bile ducts such as primary biliary cirrhosis or sclerosing cholangitis, the alkaline phosphatase and GGT activities are often elevated along with the direct bilirubin concentration. (See Gilbert's Syndrome)
Albumin - Albumin is the major protein that circulates in the bloodstream. As it is made by the liver and secreted into the blood it is a sensitive marker and a valuable guide to the severity of liver disease.
Low serum albumin concentrations indicate the liver is not synthesizing the protein and is therefore not functioning properly. The serum albumin concentration is usually normal in chronic liver diseases until cirrhosis and significant liver damage is present. There are many other proteins synthesized by the liver however the albumin is easily, reliably and inexpensively measured.
Platelet count - Platelets are cells that form the primary mechanism in blood clots. They're also the smallest of blood cells. They are derived from the bone marrow from the larger cells known as megakaryocytes. Individuals with liver disease develop a large spleen. As this process occurs, platelets are trapped within the sinusoids (small pathways within the spleen) of the spleen. While the trapping of platelets is a normal function for the spleen, in liver disease it becomes exaggerated because of the enlarged spleen (splenomegaly). Subsequently, the platelet count may become diminished.
Prothrombin time (Clotting Studies) The prothrombin time is tested to evaluate disorders of blood clotting, usually bleeding. It is a broad screening test for many types of bleeding disorders. When the liver is damaged it may fail to produce blood clotting factors.
How do the liver cell membranes get damaged in the first place?
Inflammation is a common cause of damage to the delicate liver cell membranes. Liver inflammation is medically termed hepatitis (hepato = liver, itis = inflammation).
This has many different causes including long term alcohol excess, some medications such as long term antibiotics, cholesterol lowering medications and pain killers, oral synthetic hormone replacement, viral infections of the liver such as hepatitis A, B & C, auto-immune hepatitis, hemachromatosis, primary biliary cirrhosis, exposure to toxic chemicals such as insecticides & pesticides & organic solvents & incorrect diet.
Fatty liver can cause raised Liver Function Test results
One of the most common causes of liver inflammation is fatty liver (see section on Fatty Liver). Fatty liver is also known as NASH, which stands for Non- Alcoholic Steatorrhoeic Hepatosis. It is very common in overweight persons, over the age of 30 who have had a long term poor diet high in processed foods, sugar, saturated fat and dairy products.
Generally an ultrasound of the abdominal area should also be performed. Many cases of fatty liver can be picked up this way. The ultrasound will detect areas ‘of increased echogenicity' meaning that the liver tissue is beginning to become infused with fat.
What can be done to lower the readings?
In my medical practice where I do a lot of routine blood tests for hormone levels and liver function in overweight patients, I often find slight elevations in liver enzymes which signifies mild impairment of liver function and slight liver damage. This can easily be reversed with "The Liver Cleansing Diet" principles and specific dietary supplements. I have found that it is very difficult for many of my overweight patients to lose weight even though they may be eating only normal amounts, unless I first improve their liver function. Once they are five to six weeks into the "Liver Cleansing Diet" their liver-function tests are usually back to normal and the process of weight loss takes on increased momentum. Yes, the liver is the strategic organ for those who have found it very difficult to lose weight or simply just to maintain a healthy weight as they get older.
TESTS FOR LIVER DISEASE
If you suspect that your liver is not working properly or may be diseased, ask your doctor to check your liver. The liver can be seen with various imaging techniques, such as ultrasound scanning or CAT scanning, which are done by a radiologist. An ultrasound scan of the upper abdomen will show the size and shape of the liver, gallbladder, spleen, and pancreas. CAT scanning is used to check for cancer or tumors of the liver.
Blood tests can check levels of serum bilirubin and bile acids, which may be elevated in certain types of liver and gallbladder disease. If the bilirubin is too high you may also notice that your bowel actions are very pale and that your urine is a darker color because bilirubin is diverted from the bowels to the urine.
When diagnosing liver disease, often, but not always the most used test in each disease is generally: