Differences Between IFE & SPE Protein

Serum protein electrophoresis (SPE) and immunofixation electrophoresis (IFE) are methods used for the detection of proteins, called immunoglobulins, in patients with multiple myeloma, a cancer of the muscle tissue. Both of these methods are used to identify globulin proteins present in the blood for the diagnosis of the disease. Although both processes are capable of separating protein molecules, the IFE method is approximately 10 times more sensitive.

Electrophoresis

• Electrophoresis is a process to separate molecules based on their relative size and charge. Samples are placed in a gel made of agarose and an electrical charge is applied to the gel while in a buffer solution. Protein molecules have a negative charge and will travel towards to cathode, or positive post, of the electrophoresis apparatus. The proteins will also separate due their size: the smaller molecules will travel at a greater speed than the larger ones.

Serum Protein Electrophoresis

• For either the SEP or IFE method, blood must first be collected from the patient and then the protein immunoglobulins are separated by electrophoresis. These proteins are separated into five distinct classes: serum albumin; alpha-1 and 2 globulins, beta globulins and gamma globulins. The SPE method is a relatively simple procedure that is well established and can offer quantitative analysis. The disadvantages of the method include less sensitivity of immunoglobulins at lower concentrations and the subjective interpretation of the results.

Immunofixation Electrophoresis

• The IFE method is also well established and can be used for the detection of immunoglobulins in blood and urine samples. This method is also sensitive for proteins at concentrations of up to 150 milligrams per liter. However, this sensitivity is not useful for normal levels of some proteins. Additionally, this process requires the use of antisera, which is expensive to produce.

Considerations

• There are several issues that should be considered when choosing which method to use. Among these are sensitivity, speed, cost and interpretation of the data. Importantly, the sensitivity to the protein of interest may vary between the two. As reported by Jankowski and colleagues in "Clinical Vaccination and Immunology," blood samples "demonstrating a restricted band of protein migration on SPE demonstrated abnormal IFE patterns suggestive of multiple myeloma."