A total serum protein test is a type of blood test that measures the levels of protein in the blood. Protein is present in every cell of the body and is involved in a wide variety of functions. An abnormal serum protein test may indicate inadequate nutrition, heart failure, kidney or liver problems, high blood pressure (hypertension), an infection of the heart valves(endocarditis), or a variety of other conditions. Blood protein tests are most commonly used to evaluate kidney and liver function.
Some medications can interfere with the results of the test, and people are strongly urged to follow their physician’s orders regarding how to take their medication before the test in order to ensure the test’s accuracy.
About total serum protein tests
A total serum protein test is a type of blood test that measures the levels of protein in the blood. Measuring these levels can give physicians valuable information about a patient’s nutritional state and kidney and liver functions.
Proteins are chains of amino acids, which are the building blocks of every cell in the body. Some proteins serve as enzymes, facilitating chemical reactions. Others have roles in oxygen transport, cholesterol transport, blood clotting, bone structure or fighting infection. Once produced, proteins only stay in the body for 12 to 18 days before they are broken down (metabolized). Their amino acids are then used to make new proteins, hormones, enzymes or other substances needed by the body. A damaged liver is no longer able to produce proteins, and serum protein levels will drop significantly within two weeks of liver damage.
There are two types of proteins found in the blood that are measured by total serum protein tests:
Albumin. Albumin is produced by the liver and removed from the body by the kidneys through urine. Albumin is mostly found in plasma – the liquid portion of the blood in which blood cells are suspended. Albumin’s primary role in the body is to transport small molecules, such as calcium, around the body. Albumin also helps keep blood fluids from leaking out into tissue. Albumin levels in the blood are primarily used to diagnose malnutrition or kidney, liver or gastrointestinal disorders. Low levels of albumin may lead to leakage of fluid outside the capillaries (tiny blood vessls) with fluid accumulation under the skin (edema) and the body spaces.
Globulins. Globulins are a group of proteins. Some are produced in the liver and others are formed by the immune system. Globulins have a wide variety of functions, including transporting metals such as iron and helping to fighting infection. If necessary, a test called serum protein electrophoresis may be used to separate globulins into their subcategories:
Alpha-1 globulins. The two primary alpha-1 globulins are antitrypsin and haptoglobin. Antitrypsin is an enzyme found in the lungs. Haptoglobin prevents the kidneys from removing the oxygen-carrying enzyme hemoglobin from the body.
Alpha-2 globulins. These globulins are released as part of the body’s response to inflammation, injury or illness.
Beta globulins. These mainly include transferrin and LDL (“bad”) cholesterol. Transferrin carries iron, and LDLs transport fats through the blood.
Gamma globulins. These are also known as immunoglobulins because they are antibodies, released during autoimmune disease and in response to infection, allergic reactions or foreign materials in the body such as a heart transplant. They may also be released in response to chronic inflammatory disorders or some forms of cancer.
The serum protein test measures the level of total protein (albumin plus globulin), albumin and globulins in the blood. A value called the albumin to globulin ratio (A/G ratio) can be calculated by dividing the amount of albumin by the amount of globulin. Blood serum normally contains more albumin than globulin, so the A/G ratio should be greater than one.
Protein testing is usually performed to diagnose the cause of symptoms when they first begin. It is also used to monitor the progress of treatments and a series of regular testing over time may be required.
Factors that may affect test results
Many factors may affect protein test results, including pregnancy and recent surgery or illness. Patients should follow their physician’s restrictions on diet, exercise and medication use prior to the test. Medications that may affect blood- protein levels include some:
Antibiotics. Medications that harm or kill microorganisms and are commonly used to treat infections.
Antineoplastic agents. A broad class of cancer-fighting medication.
Alkylating agents. A type of cancer-fighting medication.
Corticosteroids. A synthetic hormone used as an anti-inflammatory agent.
Antipsychotics. Medications used in the treatment of psychosis, schizophrenia, etc.
Antituberculars. Medications used in the treatment of tuberculosis.
Anticonvulsants. Medications used in the treatment of convulsions and seizures.
Salicylates. Pain relieving and fever reducing medications, including aspirin, often used in the treatment of arthritis.
Antidiabetics. Medications that stimulate the production of insulin in the pancreas or cells' sensitivity to insulin, used for treatment of patients with type 2 diabetes. Insulin injections needed by diabetes patients whose bodies are no longer able to produce insulin can also affect protein levels.
Androgens. Male hormones naturally found in the body that are used in the treatment of some breast cancers in females and delayed puberty or other conditions in males.
Estrogens. Female hormones otherwise naturally found in the body used in the treatment of some conditions and as a part of hormone replacement therapy.
Birth control pills. Also female hormones, used to inhibit the reproductive cycle of women and prevent pregnancy.
Understanding total serum protein results
Protein tests may be measured in grams per deciliter (g/dL) or milligrams per deciliter (mg/dL) depending on the laboratory performing the test. Although there may be some variation in reference ranges among labs, normal blood levels measured in grams per deciliter are as follows:
Total serum protein: Normal levels are 5.5 to 9.0 g/dL
Albumin: Normal levels are 3.5 to 5.5 g/dL
Globulins: Normal levels are 2.0 to 3.5 g/dL
A/G ratio (albumin to globulin ratio): Normal levels are greater than one
If a serum protein electrophoresis was done, then results will be compared to normal levels of the globulins’ components, which (in grams per deciliter) are as follows:
Alpha-1 globulin: Normal levels are 0.1 to .4 g/dL
Alpha-2 globulin: Normal levels are 0.5 to 1 g/dL
Beta globulin: Normal levels are 0.7 to 1.2 g/dL
Gamma globulin: Normal levels are 0.5 to 1.6 g/dL
An abnormal total serum protein test may be a sign of high blood pressure(hypertension), an infection of the heart valves(endocarditis), tuberculosis or a gastrointestinal problem.
An abnormally high level of albumin may indicate severe dehydration (loss of water from the body). Abnormally low levels may signal malnutrition, liver or kidney disease, lupus, rheumatoid arthritis, Hodgkin disease, uncontrolled diabetes, hyperthyroidism or heart failure.
Elevated globulin levels can be seen in autoimmune diseases such as lupus or rheumatoid arthritis, cancer, kidney or liver disease, infection, multiple myeloma (a bone cancer), or Hodgkin disease (cancer of the lymphatic system). Abnormally low levels can indicate malnutrition, gastrointestinal diseases such as Crohn’s disease, liver or kidney disease, blood clotting problems, emphysema, leukemia, hemolytic anemia, or problems with the immune system.
Questions for your doctor
Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions related to the total serum protein test:
Why do I need to take a total serum protein test?
Do you suspect I have damage to my kidneys or liver?
What will a total serum protein test be able to tell you about my health?
Is this type of test safe?
Will the test hurt in any way?
Do I need to make any special preparations for the test?
Am I currently taking any medications that might interfere with the test results?
When will I find out my test results? Will someone contact me with the results?
Will there be someone available to discuss my test results with me?
Could the fact that I am pregnant influence test results? Could the test harm my unborn child in any way?
