Prealbumin

Prealbumin is a transport protein in the body that can be measured to determine if a patient is malnourished or needs nutritional support. The name prealbumin is actually a misnomer, as this protein is not related in structure to albumin. The formal name for prealbumin is transthyretin. This protein is made primarily in the liver and is used by the body to transport T3 and T4. While prealbumin contains both binding sites for T3 and T4 it usually only carries one of these molecules at a time.Prealbumin has a high proportion of essential to non-essential amino acids and a high content of tryptophan. Along with a half-life of two days, the proportion of amino acids inside prealbumin make it an ideal marker for nutritional status. Prealbumin is classified as an acute phase reactant. As such, concentrations will decrease naturally in the event of inflammation. Other acute phase reactants such as CRP can be run in tandem with prealbumin in order to rule out decreased concentrations due to inflammation.

The concentration of prealbumin in a patient’s serum will increase or decrease rapidly in response to a patient’s nutritional status. Increases in concentration can occur due to drug therapy with high-dose corticosteroids or high-dose nonsteroidal anti-inflammatory drugs. Increases in prealbumin can also be seen in Hodgkin’s disease and kidney failure. It is not typical to use prealbumin testing to monitor these conditions. Decreases in the concentration of prealbumin are more serious and are a sign of malnutrition. A decreased concentration of prealbumin can be found in chronic illnesses such as cancer or AIDS, in patients with hyperthyroidism, in sepsis, and in liver disease. Other conditions that can lead to malnutrition include protein-losing gastrointestinal illnesses, eating disorders such as anorexia, massive trauma, pancreatitis, and severe burn victims. All of these diseases and disorders can result in a decreased concentration of prealbumin.

Prealbumin levels can also be used to monitor the effectiveness of nutritional therapy. Physicians will order prealbumin levels on patients who are scheduled for surgery or hemodialysis in order to determine if a patient will have a negative or diminished outcome to treatment. Patients with a normal prealbumin level are better nourished and will recover more quickly from these types of treatments. Prealbumin levels can also be used to monitor the effectiveness of parenteral nutrition therapy. If a patient is responding to nutritional therapy then prealbumin levels should increase about 1 mg/dL per day.

Normal ranges for prealbumin concentration can vary slightly between laboratories however a general range is 20-40 mg/dL. Here at BSHS we are running prealbumin on the Dimension Vista system. This assay detects the concentration of prealbumin in serum using an antiserum. The antiserum combines with the prealbumin to form immune complexes that are detected via nephelometry. These immune complexes create light scatter that is directly proportional to the concentration of prealbumin in the sample.

Prealbumin is an ideal marker for nutritional status. It has a short half-life and reacts quickly to changes in a patient’s diet. It contains within it a wide variety of essential and non-essential amino acids that are used throughout the body. Because of its structure it is a better marker for nutritional status than albumin levels alone. When available it is the preferred test for determining the nutritional status of a patient.

References
· Burtis, C. A., Ashwood, E. R., Bruns, D. E., Tietz Textbook of Clinical Chemistry & Molecular Diagnostics. St. Louis, Missouri: Elsevier (2006). 563-564.
· SIEMENS Dimension Vista Flex reagent cartridge. (2008). Prealbumin. (REF K7064). Newark, DE: Siemens Healthcare Diagnostics Inc.
· Prealbumin. (2009). Prealbumin: The Test. Lab Tests Online. Retrieved on July 24, 2010 from http://www.labtestsonline.org/understanding/analytes/prealbumin/glance.html#
· Prealbumin. (2010). Prealbumin. Clinlab Navigator. Retrieved on July 24, 2010 from http://www.clinlabnavigator.com/index.php?option=com_content&view=aritcle&id=473&letter=P