Protein electrophoresis is a medical procedure that is used to separate and analyze the proteins present in a fluid sample. The sample to be tested is usually a specimen of urine or blood. Cerebrospinal fluid may also be tested using this technique.
Separation of protein molecules in electrophoresis is performed using an electrical charge. First, the protein molecules are treated to give them a negative magnetic charge. Then, the sample is placed on or into a substrate, usually some kind of gel, to which an electric field is applied. Before the invention of electrophoresis gels, early protein electrophoresis techniques made use of special kinds of paper as a substrate.
Due to the charge on the protein molecules, they gradually move towards the positive side of the electrical field. The protein molecules are separated out by size, because the smaller molecules travel faster than the larger ones. A dye is usually needed in order to make the proteins visible.
Serum protein electrophoresis is a specific electrophoresis test that is used to identify proteins, called globulins, which are present in blood serum. Some disorders that may be diagnosed using this test include cirrhosis, liver disease, anemia, and a number of different types of cancer. A low level of the protein called albumin, for example, may indicate liver disease. Haptoglobin and macroglobulin are two proteins that often show reduced levels in certain kinds of anemia.
Normal urine contains extremely low levels of protein. Urine protein electrophoresis is usually performed after a doctor has diagnosed elevated levels of protein in the urine of a patient. An example of a protein that is often present in elevated amounts in the urine, when the patient has a kidney problem is the Bence Jones protein. Gel electrophoresis of the various different proteins present in the urine may help to identify specific kidney diseases that could be causing the proteins to be excreted. Because urine and cerebrospinal fluid tend to have much lower levels of protein present than is the case for blood serum, a concentration procedure is usually required prior to performing protein gel electrophoresis on urine or cerebrospinal fluid specimens.
As well as its important uses in diagnosis, the protein electrophoresis is often used to monitor ongoing conditions. Measuring the levels of the protein that is indicative of a disorder being treated may be an important way to determine whether the disease is progressing, and to measure the success or failure of a prescribed drug or treatment. This kind of monitoring is typically used for progressive kidney and liver disorders, and for some autoimmune diseases.