The liver is one of the quietest and busiest workers in our body. It does a lot of work without us even realizing it. From helping to digest food to eliminating toxins from the body, its list of duties is long. So sometimes we need to check if there is something wrong with this hard-working liver, if it is tired, and if it is doing its job properly. Fortunately, we can find out a lot about this with a simple blood test. Today we are talking about the 'Liver Function Tests', known to everyone as LFTs.
Simply put, what is this Liver Function Test (LFT)?
It's very simple. LFTs are a series of tests that use a small blood sample taken from a vein in your arm. They measure the amount of various substances (such as enzymes and proteins) that are produced by your liver or that accumulate in your blood when your liver is damaged.
Imagine you take your car in for service. The mechanic measures things like the engine oil and coolant to get an idea of the condition of the engine, right? In the same way, a doctor checks the levels of these things in your blood to get an important idea of the health and functioning of your liver.
Why would a doctor tell you to do this LFT?
There may be several reasons why your doctor may recommend this test.
- Check for suspected liver disease: If you have symptoms that look like jaundice, yellow eyes, pain in the right side of your stomach, or feeling lethargic, you may be asked to do this test because you suspect hepatitis or another disease.
- Monitor pre-existing liver disease: If you already have liver disease (for example, cirrhosis), this test is done regularly to see how it is doing, whether the disease is worsening, or whether it is under control.
- See if the treatment is successful: This test also helps to determine whether the medications given for a liver disease are working and whether the disease is improving.
- Monitor the side effects of medications you are taking: Some medications, such as cholesterol-lowering drugs and long-term painkillers, can affect the liver. So, when you use such medications, doctors also do this LFT to check if there is any effect on the liver.
What are the main things that are looked at in an LFT?
When you look at an LFT report, you'll see a bunch of English letters and numbers. At first glance, it may seem a bit complicated, but each of these numbers tells you about different aspects of liver function. Let's take a look at what these key things are.
| Test Name | What does this mean? |
|---|---|
| Liver Enzymes ALT, AST, ALP, GGT | These are the most well-known. When liver cells are damaged, injured, or inflamed, these enzymes are released into the blood. So if their levels are elevated in the blood, it means that the liver is under some stress. |
| Total Protein and Albumin | The liver makes many of the proteins our bodies need. Albumin is one such key protein. When the liver is not working properly, the production of this protein decreases. This can cause low protein levels in the blood. |
| Bilirubin | This is a yellow waste product that is formed when red blood cells break down. A healthy liver takes this bilirubin, combines it with bile, and removes it from the body. When the liver has a problem, this function does not work properly. Then bilirubin accumulates in the blood, causing the eyes and skin to turn yellow. We also call this 'yellow fever'. |
| Prothrombin Time (PT) | The liver also makes special proteins (clotting factors) that help blood clot. The PT test measures how long it takes for your blood to clot. If the liver is damaged, the production of these proteins decreases. This increases the time it takes for blood to clot. |
Is this blood test difficult to do?
Not at all. This is very simple and can be done in a few minutes.
When you go to a hospital or lab, a nurse or technician will find a vein in your arm near your elbow and clean the area. Then, using a small needle, they will collect a small amount of blood into a vial. You may feel a slight stinging sensation, but it will quickly go away. After the blood is drawn, the sample is sent to a lab. It may take a few hours or a day or two for the results to come back.
The most important thing is to ask your doctor whether you need to fast before this test. Sometimes, you may be asked to fast because it is done in conjunction with other tests.
How to understand the values in the report? (Normal Ranges)
When you receive your report, you will see your score for each test, along with the 'Normal Range'. But there is one very important thing to remember here.
Don't panic or decide that you have a disease when you see the values in this report. Only your doctor can understand this accurately and come to a conclusion tailored to your situation.
Because the normal range of values can vary slightly from lab to lab. These values can also vary depending on factors such as age and gender.
Here are some commonly used value ranges:
| Test | Normal Range |
|---|---|
| Alanine transaminase (ALT) | 0 to 45 IU/L |
| Aspartate transaminase (AST) | 0 to 35 IU/L |
| Alkaline phosphatase (ALP) | 30 to 120 IU/L |
| Bilirubin | 2 to 17 micromoles/L |
| Prothrombin time (PT) | 10.9 to 12.5 seconds |
| Albumin | 40 to 60 g/L |
What does elevated ALT and AST levels mean?
The first thing that most people pay attention to in an LFT report is the two enzyme levels, ALT and AST. If these are elevated, it indicates that there is some damage to the liver cells.
However, doctors also look at the ratio of these two values. For example, if the AST value is about twice as high as the ALT value, it often indicates liver damage due to alcohol use. If both values are about the same, it may be due to another cause (for example, a viral infection).
What kind of diseases does LFT indicate?
This is something we need to understand. The LFT test is just the first step in the diagnostic journey. It is like the first clue a detective gets. The results of this test alone cannot definitively confirm a disease. However, it gives the doctor a good guide as to where the problem lies and what to do next.
If the LFT results are abnormal, further tests may be needed, such as an ultrasound scan, other specialized blood tests, and possibly a liver biopsy.
Some of the conditions that LFT tests can indicate are:
- Fatty Liver Disease
- Liver damage due to toxins (Toxic Hepatitis)
- Viral hepatitis (Viral Hepatitis A, B, or C)
- The body's own immune system attacks the liver (Autoimmune Hepatitis)
- Cirrhosis - scarring and shrinkage of the liver
- Bile duct problems
- Liver Cancer
- Hereditary diseases such as hemochromatosis
Take-Home Message
- A Liver Function Test (LFT) is a very simple and safe blood test that provides a lot of information about the health of your liver.
- Once you receive the results of this test, don't jump to conclusions based on information on the internet. That will only create unnecessary fear.
- Only your doctor can give you an accurate interpretation by comparing the values in your report with your symptoms and other medical information.
- Not every time LFT values are elevated, it means there is a serious illness. Sometimes it can be a simple cause, such as a medication you are taking or a temporary infection. But it is important to investigate it.
- The liver is a valuable organ that works silently. Therefore, if a doctor recommends it, it is very important to conduct a test like this to check the health of the liver.
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