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The albumin blood test is ordered when signs of liver disease or kidney disease are present. This includes symptoms such as weight loss, fatigue, jaundice and swelling of the eyes, legs or stomach. The albumin blood test can also help monitor a person's nutritional profile while on restricted diets. It can help identify protein deficiencies and malnutrition, usually in combination with another blood test called the prealbumin test.
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What Does the Test Measure?
The blood test for albumin measures the level of albumin in the liquid portion of the blood, also known as the blood serum. Albumin is a soluble protein that is responsible for transporting certain molecules throughout the body, including hormones, vitamins, drugs and ions. Albumin also prevents fluid in the blood vessels from leaking out into the surrounding tissue by maintaining an adequate osmotic pressure.
Albumin is made in the liver as preproalbumin and processed to become proalbumin. Before it is released from the liver cells, proalbumin is converted to albumin. Albumin constitutes one-half of all proteins in the blood serum.
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How is the Test Performed?
The albumin blood test requires a blood sample drawn from a vein with a needle. Certain medications can increase the level of albumin in the blood, such as anabolic steroids, growth hormone, insulin and androgens. The doctor will determine whether or not these medications will interfere with the results.
The blood sample is placed in a centrifuge to separate the cells from the liquid portion of the blood. The liquid portion is then analyzed for albumin. A dye such as bromocresol green or bromocresol purple is added to the liquid portion of the blood to bind to the albumin. The sample is then placed in a spectrophotometer, which is an analytical instrument that projects a beam of light at the sample and measures the amount of light that is absorbed. The measurement is compared with a standard to determine the concentration of albumin in the blood.
The standard is a linear graph prepared from a series of pure albumin samples of known concentrations. Each sample has a corresponding absorbance measurement obtained from the spectrophotometer. Together, these measurements provide a range within which the absorbance of the tested blood sample will fall.
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Albumin Test Results
The normal range for serum albumin is between 3.4 and 5.4 grams per deciliter. A serum albumin concentration below the normal range indicates liver damage associated with hepatitis and cirrhosis. Low serum albumin levels can also indicate poor absorption of nutrients and kidney problems.
A serum albumin concentration above the normal range usually indicates dehydration. The lack of water reduces the blood volume, causing the albumin concentration in the blood to rise.
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1. "Albumin: The Test." Lab Tests Online. American Association for Clinical Chemistry. 18 Jun. 2010. Web. 6 Jul. 2010.
2. Dugdale, David C. "Albumin-Serum." MedlinePlus. U.S. National Library of Medicine. 23 Feb. 2009. Web. 6 Jul. 2010.
3. "BCP Albumin Assay." Assay Depot. 2010. Web. 6 Jul. 2010.
4. Doumas, David C. "Albumin Standards." Science Direct. 9 Feb. 1998. Web. 6 Jul. 2010.