Serum protein electrophoresis

The expected result is 'No paraprotein detected' or 'No monoclonal band'. When a paraprotein is found, the laboratory names its type (for example IgG kappa) and usually gives its amount in g/L. A small paraprotein is found in about 3 in 100 adults over 50 in the general population, most of whom never develop any related illness.

Serum protein electrophoresis separates the proteins in the blood into bands according to their size and electrical charge. Healthy antibodies come from thousands of different cell clones and form a broad smear; when one clone has multiplied and is making a single antibody, it shows up as a sharp extra band, called a paraprotein, M protein or monoclonal band. Immunofixation is a further step that identifies exactly which type of antibody the band is.

Doctors request it when looking at myeloma and related conditions, in unexplained kidney disease, bone pain, anaemia, a high ESR or plasma viscosity, or a high total protein, and to follow people with a known paraprotein over time.

• Monoclonal gammopathy of undetermined significance, a small paraprotein found in about 3 in 100 adults over 50 in the general population
• Myeloma and related conditions such as Waldenstrom's macroglobulinaemia and amyloidosis
• Some lymphomas and other blood conditions
• Long-term infections and some autoimmune conditions, which occasionally produce a small band

• No paraprotein is the usual finding; there is no lower limit
• Treatment of the condition producing the band brings the amount down
• Some small bands come and go, particularly after infections

• A small paraprotein becomes more common with age, and most people who have one never develop any related illness
• A very faint band on one method may not be seen on another
• Some medicines, notably some antibody-based treatments, appear as a band of their own on the trace

No fasting needed. It is read alongside immunoglobulins, free light chains and, when a band is found, immunofixation. In people with a known paraprotein the amount in g/L is followed over time.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.