Total protein

Changes in total protein concentration are common. An elevated total protein concentration may mean the presence of a paraprotein. A decreased total protein usually means that the albumin concentration is low.

Albumin

Albumin is the major plasma protein and is synthesized and secreted by the liver. It has a biological half-life in plasma of about 20 days and it accounts for about 50% of the total hepatic protein production. Albumin makes the biggest contribution to the plasma oncotic pressure. If the albumin concentration falls very low, oedema is the result (Fig 25.1). There are four main reasons for the occurrence of a low plasma albumin concentration:

Although serum albumin measurements have previously been used to monitor a patient’s response to long-term nutritional support, they are unreliable and insensitive.

Specific proteins

Measurement of a number of specific proteins gives useful information in the diagnosis and management of disease (Table 25.1). Characteristic changes in the concentration of certain plasma proteins are seen following surgery or trauma, or during infection or tumour growth. The proteins involved are called acute phase reactants (pp. 110–111). These acute phase proteins may be used to monitor progress of the condition or its treatment.