Prealbumin, also known as transthyretin, is a protein primarily manufactured by the liver and released into the bloodstream. It transports substances throughout the body, including thyroid hormones and vitamin A (retinol). Measuring prealbumin levels in the blood offers insights into an individual’s overall health status.
What is Prealbumin?
Its scientific name, transthyretin, highlights prealbumin’s function: transporting thyroxine, a thyroid hormone, and binding to retinol-binding protein to carry vitamin A throughout the body. This transport ensures these molecules reach various tissues and organs for proper cellular function and energy regulation.
A distinguishing characteristic of prealbumin is its relatively short half-life, typically around two to three days. This rapid turnover rate makes prealbumin levels highly responsive to recent changes in the body’s protein and calorie status.
Why is Prealbumin Measured?
Prealbumin testing serves as a sensitive marker for assessing nutritional status, particularly in situations involving acute changes in health. Since its levels respond quickly to dietary intake and metabolic demands, it helps determine if an individual is receiving adequate nutrients, especially protein. This is particularly useful for patients who are hospitalized, undergoing surgery, or managing chronic illnesses that affect nutrient absorption.
The test can also monitor the effectiveness of nutritional support interventions, such as intravenous feeding. A rise in prealbumin levels indicates that nutritional therapy is having a positive effect on the patient’s protein and energy balance. Many providers find it valuable for tracking nutritional health in seriously ill or hospitalized individuals.
Interpreting Prealbumin Levels and Their Implications
Interpreting prealbumin levels requires careful consideration, as various factors beyond nutrition can influence them. A normal adult range typically falls between 15 to 36 milligrams per deciliter (mg/dL), though these values can vary slightly between laboratories. Healthcare professionals usually assess these results in conjunction with other clinical information and tests, such as C-reactive protein (CRP), to gain a comprehensive understanding.
Low prealbumin levels, often below 15 mg/dL, commonly suggest protein-calorie malnutrition. This can stem from insufficient dietary intake, eating disorders, or conditions that increase nutrient requirements, such as severe infections, inflammation, trauma like burns, liver disease, or certain digestive disorders. Steadily dropping prealbumin values have been associated with reduced survival rates in some patient populations.
Conversely, high prealbumin levels are less common but can occur in specific situations. These may include kidney failure, Hodgkin’s lymphoma, pregnancy, or conditions involving iron deficiency or hyperactive adrenal glands. Certain medications, such as anabolic steroids, androgens, prednisolone, and high-dose non-steroidal anti-inflammatory drugs, can also increase prealbumin concentrations. Prealbumin tests are not typically used to diagnose these specific conditions, but rather to provide a piece of the overall health puzzle.
Prealbumin vs. Albumin: Key Differences
Both prealbumin and albumin are proteins produced by the liver, and both have historically been used to assess nutritional status. However, their different half-lives make them useful for evaluating different aspects of health. Prealbumin has a relatively short half-life of approximately two to three days, meaning its levels respond quickly to recent changes in protein intake or acute inflammatory states. This rapid turnover allows it to serve as a more immediate indicator of current nutritional status.
In contrast, albumin has a much longer half-life of about 20 days. Consequently, albumin levels reflect a person’s nutritional history over a period of several weeks rather than immediate changes. While albumin is widely available and inexpensive to measure, its longer half-life means it is less sensitive to acute nutritional shifts and can be significantly influenced by factors like hydration status and chronic inflammation.