UNDERSTANDING YOUR LIVER FUNCTION TESTS (LFTs)
Wouldn’t it be nice if your liver came equipped with a dashboard, like the one in your car that tells you that the oil needs changing, that the engine’s overheating, or that you need to find a gas station in hurry? Since it doesn’t, doctors have come to rely on a number of blood tests—known as liver function tests (LFTs)—to give them some indication of what’s going on inside the liver. But don’t be fooled by this name. While LFTs are commonly used to reflect how well the liver is working, this name can be misleading, as it is impossible for any blood test to accurately assess all of the liver’s varied functions. Thus, like the indicator lights and gauges in a car, the LFTs are not a perfect indication of exactly what’s wrong. They can, however, alert the doctor that something is amiss with the liver. Furthermore, they can help determine which additional tests are necessary. And, when used in conjunction with these additional tests, LFTs give the doctor a better idea of what is wrong with the liver and how well the liver is working. By keeping track of the results from the LFTs over the months and years ahead, both the patient and the doctor may—in some cases—have an idea whether the liver condition has stabilized, improved, resolved or worsened; whether a specific treatment is working, or if something different needs to be tried and whether it is time to refer the patient for a liver transplant evaluation.
LFTs consist of many different blood tests that check the levels of liver enzymes (transaminases and cholestatic liver enzymes); bilirubin; and the liver proteins. The following is a discussion of these tests.
A Word About Normal Reference Ranges
When laboratory test results are reported to the doctor, these results are typically compared to values obtained from a group of healthy people. The range of these “normal values” is known as the reference range or reference interval. The high and low ends of the interval are commonly referred to as the upper and lower limits of normal. This reference range may differ slightly from one time to the next and from one laboratory to the next. This information needs to be taken into consideration when interpreting a single isolated laboratory result.
Some Final Thoughts on Blood Work
Remember, an isolated group of blood test results cannot be used to predict the future of a person with liver disease. The actual numbers themselves may have little significance. Their meaning is only important in conjunction with a multitude of other factors, each of which must be carefully interpreted by a doctor. In other words, don’t get too hung up about the individual numbers. Each is just one piece of a very large puzzle. In most cases, the numbers are just a clue that something is wrong—only the first step toward a correct diagnosis.
After the routine blood tests are evaluated, more specific blood work is usually required in order to pinpoint an exact cause of liver abnormalities. Table 3.1 on page 31 lists the blood tests that are used to diagnose specific liver diseases. These blood tests will be discussed in more detail throughout the book. Usually, the laboratory provides the doctor with the results of routine blood work within a day or two; but the results of more specific blood tests may take up to two weeks, depending on the laboratory. The waiting period may not be easy. (Try to be a patient patient.)
All contents of this article are Copyright © Melissa Palmer, MD
Melissa Palmer, MD is the author of " Dr. Melissa Palmer's Guide of Hepatitis and Liver Disease". (Published 2004. Penguin Putnam).
The offices of Melissa Palmer, M.D. are located at:
1097 Old Country Road Suite 104
Plainview, N.Y 11803
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