Total Protein and A/G Ratio

Total protein and albumin are routinely included in the panels of tests performed as part of a physical, such as a Comprehensive Metabolic Panel (CMP), so they are frequently assessed as a part of an evaluation of a person's overall health status.

Additionally, 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 ordered in a variety of settings to help diagnose disease, to 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 used to screen for and help diagnose kidney disease or liver disease, for example. 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 low or high so that a specific diagnosis can be made. Some examples of follow-up tests include protein electrophoresis and quantitative immunoglobulins.

When is it ordered?
A total protein test is frequently ordered as part of a Comprehensive Metabolic Panel (CMP). This panel of tests is often performed when an individual undergoes a routine health checkup. Total protein may also be ordered to provide general information about a person's nutritional status, such as when someone has undergone a recent, unexplained weight loss. It can be ordered 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 (edema).

What does the test result mean?
Results of a total protein test are usually considered along with those from other tests of the CMP 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.

• A low total 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 celiac disease or inflammatory bowel disease (IBD).
• A high total protein level may be seen with chronic inflammation or infections such as viral hepatitis or HIV. It also may 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 globulin, the A/G ratio may provide a clue as to the cause of the change in protein levels.

• A low A/G ratio may reflect overproduction of globulins, such as seen in multiple myeloma or autoimmune diseases, or underproduction of albumin, such as may occur with cirrhosis, or selective loss of albumin from the circulation, as may occur with kidney disease (nephrotic syndrome).
• A high A/G ratio suggests underproduction of immunoglobulins as may be seen in some genetic deficiencies and in some leukemias. More specific tests, such as liver enzyme tests and serum protein electrophoresis, must be performed to make an accurate diagnosis.
• With a low total protein that is due to plasma expansion (dilution of the blood), the A/G ratio will typically be normal because both albumin and globulin will be diluted to the same extent.