Reasons for ordering the prealbumin test are undergoing reassessment as understanding of prealbumin is evolving. Historically, prealbumin has been ordered to help detect protein-calorie malnutrition and to monitor the effectiveness of parenteral (for example, intravenous) nutrition. Newer evidence suggests that the reasons for changes in prealbumin levels may be more complex and the test should not be interpreted as a simple indicator of nutritional status.
No current consensus exists on when to get tested, although prealbumin may be ordered, along with assessments of nutritional intake, when a healthcare practitioner suspects that someone is malnourished or is at risk of malnutrition.
A blood sample drawn from a vein in your arm
Prealbumin, also called transthyretin, is one of the major proteins in the blood and is produced primarily by the liver. Its functions are to carry thyroxine (the main thyroid hormone) and vitamin A throughout the body. This test measures the level of prealbumin in the blood.
Although commonly used as a marker of malnutrition, research is continuing in order to better understand the role(s) of prealbumin in the body, especially the reasons for changes observed during illness, and the clinical utility of prealbumin testing.
How is it used?
Until recently, the prealbumin test was believed to be a useful marker of nutritional status and was used to help detect and diagnose protein-calorie malnutrition as well as to monitor people receiving total parenteral nutrition (TPN, getting nutrition via a solution injected into a vein). It was also used to monitor changes in nutritional status in someone undergoing hemodialysis as part of treatment for kidney disease.
Some healthcare practitioners continue to use the test in this manner; however, there is controversy because changes in prealbumin may actually reflect other conditions such as inflammation, infection, or trauma. As such, it has been suggested by some health professionals that the prealbumin test should no longer be used to assess nutritional status or diagnose malnutrition. However, others believe that the test can be useful in determining prognosis for people who are critically ill, hospitalized, and/or at risk of poor outcomes and can prompt nutritional and other support that may improve patient outcomes.
When is it ordered?
With the caveats stated above, a prealbumin test may be ordered by some healthcare practitioners when signs and symptoms of malnutrition are present or when a person is felt to be at risk for malnutrition, such as during a critical or chronic illness, hospitalization, or when receiving parenteral nutrition or undergoing hemodialysis. It may also be ordered to aid in the determination of the severity of a patient's illness.
What does the test result mean?
Normal prealbumin levels vary according to age and sex.
A low level of prealbumin may be seen with:
- Severe or chronic illness
- Trauma, such as burns
- Liver disease
- Serious infections
- Certain digestive disorders
Given the ongoing discussion of the appropriate use of this test as researchers continue to explore the role of prealbumin in the body and what changes in its level in the body reflect, interpretation of prealbumin results is challenging. Some suggest that a single prealbumin result is less meaningful that a series of measurements taken several days apart, along with other clinical assessments and laboratory tests. For example, measures of inflammation, such as C-reactive protein (CRP), may be ordered to aid in interpretation of the prealbumin results.
A high level of prealbumin may be seen in certain conditions, but the test is not used for diagnosis or monitoring in these situations.
Is there anything else I should know?
Drugs such as amiodarone, estrogens, and oral contraceptives (birth control pills) can decrease prealbumin levels. Anabolic steroids, androgens, prednisolone, and high-dose non-steroidal anti-inflammatory medications can increase prealbumin concentrations.
What is the difference between prealbumin, serum/plasma albumin, and urine albumin tests?
Although the names are similar, prealbumin and albumin are completely different molecules. They are both proteins made by the liver, however, and both have been used historically to evaluate nutritional status. Serum/plasma (or blood) albumin is now more often used to screen for and help diagnose liver or kidney disease and is tested on a blood sample. The urine albumin test (in the past, called a microalbumin test) detects and measures albumin in the urine as an early indicator of kidney damage.