|SydPath Information Sheet||
Dr Graham Jones
the most abundant protein in human serum. It has a molecular weight of about 65,000 and
consists of 584 amino acids and contains no carbohydrate. Albumin is produced exclusively
in the liver and secreted directly into the circulation. Physiological roles includes
maintenance of oncotic pressure (albumin provides 80% of the plasma oncotic pressure) and
transport of small molecules such as calcium, unconjugated bilirubin, free fatty acids,
cortisol and thyroxine. Albumin also binds drugs in the serum, egphenytoin, warfarin,
phenylbutazone and clofibrate.
The half-life of albumin in the circulation is about 20 days and the liver has large reserves of albumin synthetic capacity. Although albumin is the most abundant serum protein, it contributes little to the osmolality as the concentration is about 0.6 mmol/L when expressed in SI units.
Serum albumin is a useful marker of chronic liver disease and nutritional status, although consideration must be given to other factors contributing to the level.
Low concentrations of serum albumin may be caused by artefact, decreased albumin production, increased loss, or redistribution in the body.
Note that low serum albumin does not occur in uncomplicated acute viral hepatitis, and a normal serum albumin makes the diagnosis of cirrhosis unlikely.
Effects of low plasma albumin
The effects of low plasma albumin are mainly related to maintenance of fluid in the circulating compartment. With reduced levels of serum albumin fluid may escape into tissues to cause oedema or into body cavities to cause ascites or pleural effusions. Extremely low albumin may also affect the delivery of nutrients to tissues by the formation of localised tissue oedema. Reduced or increased levels of albumin in a sample will affect the measurement of total serum calcium, with low albumin producing a low serum total calcium (and vice versa). These conditions do not indicate a disorder of calcium metabolism.Indications for Measurement (top of page)
Albumin should be measured whenever liver disease is suspected, in cases of oedema, if malnutrition or malabsorption is suspected, or if a protein-losing state (nephrotic syndrome, protein-losing enteropathy or burns) is suspected. Albumin can be a useful monitor of these conditions but repeat measurements at intervals of less than 1 week are rarely indicated and longer intervals are appropriate in non-acute cases.
Albumin should also be measured whenever a total serum calcium is requested.
details of Albumin testing at SydPath see SydPath Test Database
|Further information available for SydPath clients from Dr Graham Jones: 8382-9160|
Pathology Service of St Vincent's Hospital, Sydney
|Last updated 30/01/2013|