What is the Difference Between Serum Protein Electrophoresis and Immunofixation?

Serum protein electrophoresis and immunofixation are laboratory techniques used to analyze proteins in blood serum, particularly in the context of diagnosing or monitoring certain diseases. The main differences between the two methods are:

1. Separation technique: Serum protein electrophoresis separates proteins based on their physical properties, such as net charge and size, using a medium like agar, cellulose, or other plant material. Immunofixation, on the other hand, is a further refinement of this technique that involves staining proteins with immunologically active agents, resulting in immunofluorescence.
2. Sensitivity: Immunofixation electrophoresis is generally considered to be more sensitive than serum protein electrophoresis. In some cases, immunofixation can detect the presence of M proteins (indicative of multiple myeloma) when serum protein electrophoresis fails to do so.
3. Purpose: Serum protein electrophoresis is commonly used to identify patients with abnormal protein levels in their blood, particularly in the context of plasma cell dyscrasias such as multiple myeloma. Immunofixation electrophoresis, also known as immunosubtraction electrophoresis, is typically ordered when an abnormal band suggestive of a monoclonal immunoglobulin is detected on either a serum or a urine electrophoresis.

In summary, both serum protein electrophoresis and immunofixation are used to analyze proteins in blood serum, but they differ in their separation techniques and sensitivity. Serum protein electrophoresis is used to identify abnormal protein levels, while immunofixation is often employed to further investigate specific abnormal bands detected in a serum or urine electrophoresis.

Comparative Table: Serum Protein Electrophoresis vs Immunofixation

Here is a table comparing the differences between Serum Protein Electrophoresis and Immunofixation:

Both techniques are used to diagnose diseases by detecting abnormal proteins or the absence of normal proteins in blood, urine, or other body fluids. However, immunofixation is more sensitive and time-consuming compared to serum protein electrophoresis. Immunofixation is particularly useful in identifying monoclonal proteins, which can be helpful in diagnosing conditions such as monoclonal gammopathy and amyloidosis.