Test for total protein

Dr Leena K *

Proteins are important building blocks of cells and tissues; they are important for body growth, development, and health. They form the structural part of most organs and make up enzymes and hormones that regulate body functions. This test measures the total amount of the various types of proteins in the liquid (plasma) portion of the blood.

Two major classes of proteins are found in the blood: albumin and globulin. Albumin makes up about 60% of the total protein. Produced by the liver, albumin serves a variety of functions including as a carrier protein for many small molecules and ions, as a source of amino acids for tissue metabolism, and as the principle component involved in maintaining osmotic pressure (preventing fluid from leaking out of blood vessels). The remaining 40% proteins in the plasma are referred to as globulins.

The globulin proteins are a heterogeneous group. They include enzymes, antibodies, hormones, carrier proteins, and numerous other types of proteins. The ratio of albumin to globulin (A/G ratio) is calculated from measured albumin and calculated globulin.

The level of total protein in the blood is normally a relatively stable value, reflecting a balance in loss of old protein molecules and production of new protein molecules.

CONDITIONS IN WHICH TOTAL PROTEIN MAY INCREASE OR DECREASE

Total protein may decrease in conditions:
o Where production of albumin or globulin proteins is impaired, such as malnutrition or severe liver disease.
o That accelerate the breakdown or loss of protein, such as kidney disease (nephrotic syndrome).
o That increase/expand plasma volume (diluting the blood), such as congestive heart failure.

Total protein may increase with conditions that cause:

Abnormally high production of protein (e.g. inflammatory disorders, multiple myeloma).

Dehydration.

The albumin-globulin ratio may change whenever the proportions of albumin and other proteins shift (increase or decrease) in relationship to each other.

SAMPLE REQUIRED

A blood sample is required for the test.

PREPARATION NEEDED

No special preparation is needed.

HOW IS THE TEST USED?

Total protein and albumin are routinely included in the panels of tests performed as a part of a general health check-up, so they are frequently assessed as a part of an evaluation of a person’s overall health status.

Since total protein can be low, increased, or the component globulin proteins altered with many different diseases and disorders, total protein and albumin tests may be done in a variety of settings to help diagnose disease, monitor changes in health status, and as a screen that may indicate the need for other kinds of testing.

Total protein measurements can reflect nutritional status and may be done to screen for and help diagnose kidney disease or liver disease. Sometimes conditions are detected with routine testing before symptoms appear. If total protein is abnormal, further testing must be performed to identify which specific protein is abnormally high or low so that specific diagnosis can be made. Examples of follow-up testing include protein electrophoresis and quantitative immunoglobulins.

WHEN IS IT DONE?

As mentioned, total protein is generally done as a part of a comprehensive health check-up. Total protein may also be done to provide general information about a person’s nutritional status, such as when someone has undergone a recent unexplained weight loss. It can also be done along with several other tests to provide information when someone has symptoms that suggest a liver, kidney, or bone marrow disorder, or to investigate the cause of abnormal pooling of fluid in tissue (oedema).

WHAT DOES THE RESULT MEAN?

Results of a total protein test are usually considered along with those from other tests and will give the doctor information on a person’s general health status with regard to nutrition and/or conditions involving major organs, such as the kidney and liver. However, if results are abnormal, further testing is usually required to help diagnose the disease affecting protein levels in the blood.

o A low protein level can suggest a liver disorder, a kidney disorder, or a disorder in which protein is not digested or absorbed properly. Low levels may be seen in severe malnutrition and with conditions that cause malabsorption, such as coeliac disease or inflammatory bowel disease (IBD).

o A high total protein level may be seen with chronic inflammation or infections such as viral hepatitis or HIV. It may also be associated with bone marrow disorders such as multiple myeloma.

Some laboratories report total protein, albumin and the calculated ratio of albumin to globulins, termed the A/G ratio. Normally, there is a little more albumin than globulins, giving a normal A/G ratio of slightly over 1. Because disease states affect the relative amounts of albumin and globulins, the A/G ratio may provide a clue to the cause of the change in protein levels.