Também conhecido como
PA
Tryptophan-rich prealbumin
Thyroxine-binding prealbumin
TBPA
Nome formal
Transthyretin test
Este artigo foi revisto pela última vez em
Este artigo foi modificado pela última vez em 10 de Julho de 2017.
At a Glance
Why Get Tested?
To help diagnose malnutrition and to monitor people at risk for poor nutrition
When To Get Tested?
When your doctor suspects that you are malnourished because of poor diet, HIV, or an eating disorder; when you are admitted to the hospital for surgery or certain diseases; or when you are having parenteral (for example, intravenous) nutrition or hemodialysis
Sample Required?
A blood sample drawn from a vein in the arm
Test Preparation Needed?
None
What is being tested?
The test measures levels of prealbumin in the blood. Prealbumin is a protein produced primarily by the liver. It serves as a source of amino acids for the production of other proteins, and it carries substances such as the thyroid hormone thyroxine throughout the body. Prealbumin has a half-life of only two days, which means that it breaks down quickly in the body and the amount changes rapidly, decreasing when there is a protein deficiency. This short half-life gives doctors a snapshot of a person's current nutritional status.

How is the sample collected for testing?

A blood sample is taken by a needle from a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.
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Accordion Title
Common Questions
  • How is it used?
    Prealbumin is ordered to help doctors detect and diagnose protein-calorie malnutrition in people who are critically or chronically ill and/or are at an increased risk for malnutrition. Protein deficiencies can occur with inadequate availability of dietary protein, decreased ability to digest protein, increased protein loss, and with increased protein requirements. They can affect the body's ability to heal, to fight infection, and can increase the risk of complications. With protein-calorie malnutrition, the body begins to break down muscle, protein, and body fat. Children with malnutrition may fail to thrive or have stunted growth.

    The prealbumin test is ordered to make an assessment of nutritional status:

    • Before a scheduled surgery
    • In patients who are hospitalized with certain conditions
    • In patients who are chronically ill

    Many people have a decline in nutrition during their hospital stay, especially after surgery. Studies have shown that good nutrition prior to surgery helps to avoid complications, such as pneumonia and infection, after surgery. If the prealbumin test indicates that someone is malnourished or has a poor nutritional status, then corrective measures can be taken before surgery and periodic prealbumin tests can be ordered as necessary after surgery to monitor the person's status.

    The prealbumin test may also be ordered to monitor changes in people who are receiving parenteral nutrition, such as intravenous treatment. It may be ordered to monitor changes in nutritional status in someone who is receiving hemodialysis, as part of treatment for kidney disease.

    A prealbumin test may be ordered by itself or along with other tests such as albumin and transferrin to evaluate nutritional status. The prealbumin test is not available in every laboratory; for this reason, an albumin test may sometimes be ordered instead of a prealbumin.

  • When is it ordered?
    A doctor orders a prealbumin test when signs of malnutrition or poor nutrition are present or when a person is at risk for protein deficiency. Signs of malnutrition include unintended weight loss, stunted growth in a child, weakened resistance to infection, or being unable to think clearly. Hair may become brittle or begin to fall out, the skin may be dry or yellowish, muscles may feel weak, and fainting spells may occur. In younger women, menstrual periods may stop.

    A prealbumin and/or albumin test may be ordered prior to surgery and whenever someone is being treated for a chronic or critical illness that may cause malnutrition. A doctor may order a prealbumin periodically to monitor someone with a low prealbumin result and to evaluate the effectiveness of treatment.

  • What does the test result mean?
    The prealbumin measurement reflects the current state of a person's nutrition. If prealbumin is low, other proteins and nutrients in the blood may also be low.

    Decreased concentrations of prealbumin may be seen in patients with:

    Low levels of prealbumin are also seen with inflammation. When inflammation and malnutrition are both present, prealbumin levels can rapidly fall to very low levels and their interpretation can be more difficult. 

Increased concentrations of prealbumin may be seen in people with:

    • High-dose corticosteroid therapy
    • Hyperactive adrenal glands
    • High-dose nonsteroidal anti-inflammatory medications
    • Hodgkin's disease
    • Kidney failure

    The prealbumin test is not typically used to monitor these conditions.

  • 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, and prednisolone can increase prealbumin concentrations.

    Recent research has shown that the prealbumin test can predict poor outcomes for hemodialysis patients. A low initial reading (baseline level) of prealbumin predicts that a patient may have an increased risk for complications, and steadily dropping prealbumin values are associated with low survival.

  • What conditions could lead to malnutrition?
    Various diseases can lead to protein-calorie malnutrition. Common diseases linked with this form of malnutrition include:
    • Cancer
    • Chronic illness
    • Protein loss in the gastrointestinal tract
    • Anorexia and other eating disorders
    • Liver disease
    • Multiple traumas
    • Obesity
    • Pancreatitis
    • Burns over 30% or more of your body
  • What is the difference between prealbumin, albumin, and microalbumin tests?
    Albumin and microalbumin are the same molecule while prealbumin, despite the similar-sounding name, is a completely unrelated molecule. The prealbumin test measures a protein that reflects your current nutritional status. Albumin testing is more often used to test for liver or kidney disease or to learn if your body is not absorbing enough amino acids. Albumin can also be used to monitor nutritional status and is a more widely available test than prealbumin. However, prealbumin changes more quickly, making it more useful for detecting changes in short-term nutritional status than albumin. The microalbumin test measures very small levels of albumin in your urine and may indicate whether you are at risk for developing kidney disease.
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View Sources
Sources Used in Current Review

Pagana, K. D. & Pagana, T. J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 755-756.

Clarke, W. and Dufour, D. R., Editors (© 2006). Contemporary Practice in Clinical Chemistry: AACC Press, Washington, DC. Pp 197.

Banh, L. (2006 October). Serum Proteins as Markers of Nutrition: What Are We Treating? Practical Gastroenterology [On-line information]. PDF available for download at http://www.healthsystem.virginia.edu/internet/digestive-health/nutritionarticles/BanhArticle.pdf through http://www.healthsystem.virginia.edu. Accessed June 2009.

Huckleberry, Y. (2004 May 03). Nutritional Support and the Surgical Patient. Medscape Today from American Journal of Health-System Pharmacy [On-line information]. Available online at http://www.medscape.com/viewarticle/474066 through http://www.medscape.com. Accessed June 2009.

Beck, F. and Rosenthal, T. (2002 April 15). Prealbumin: A Marker for Nutritional Evaluation. American Family Physician [On-line information]. Available online at http://www.aafp.org/afp/20020415/1575.html through http://www.aafp.org. Accessed June 2009.

Cassels, C. (2005 December 20). Hemodialysis, Prealbumin an independent predictor of mortality/morbidity. Medscape Medical News [On-line information]. Available online at http://www.medscape.com/viewarticle/538923 through http://www.medscape.com. Accessed June 2009.

Sources Used in Previous Reviews

The National Kidney Foundation: Kidney Disease Outcomes Quality Initiative. Available online at http://www.kidney.org/professionals/doqi/guidelines/nut_a04.html through http://www.kidney.org.

Holland DC, Meers C, Lawlor ME, Lam M. Serial prealbumin levels as predictors of outcomes in a retrospective cohort of peritoneal and hemodialysis patients. Journal of Renal Nutrition, July 2001, 11(3).

National Kidney Foundation Work Group, Committee: National Kidney Foundation-Kidney Disease Outcomes Quality Initiative. Clinical practice guidelines for nutrition in chronic renal failure. American Journal of Kidney Disease, June 2000, 35(6 Suppl 2): S1-140.

Clinical Guide to Laboratory Tests. 3rd ed. Tietz N, ed. Philadelphia: W.B. Saunders & Co; 1995: 608-609.

Frey RJ. Anorexia nervosa. Gale Encyclopedia of Medicine. Gale Research, 1999.

Larry A. Broussard, PhD. Clinical Laboratory Sciences, LSU Health Sciences Center, New Orleans, LA.

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