Myeloma cells also secrete the monoclonal immunoglobulin antibody, known as the protein M. The level of M protein in the blood and urine of a patient is used to assess the severity of the disease and to monitor treatment efficacy. The myeloma cells in some people only secrete part of the antibody which is called the light chain. The amount of M protein in the blood or urine is determined by electrophoresis of serum protein (SPE or SPEP) or electrophoresis of the urine protein (UPE or UPEP). Such tests help to see if the medication is effective and whether the disease is progressing or recurring.
Immunoglobulin levels are measured to check the antibody levels such as immunoglobulin G (IgG), immunoglobulin A (IgA), and immunoglobulin M (IgM) in the blood. In multiple myeloma, the normal levels of the antibody are low when the level of the cancer protein is high.
A serum free light chain assay is a test that can measure the amount of free light chains in the blood before the blood is filtered through the kidneys. It is a more sensitive test than urinary measurement of M protein but both are necessary to evaluate. When there is a light chain in the urine it is called the Bence Jones protein.
Often blood tests are used to assess the levels of serum albumin and serum beta-2 microglobulin (β2-M). Serum albumin is a blood protein made from the liver required to maintain adequate blood flow and general health. β2-M is a small protein that plays an important role in immune response in the body. These findings are significant in determining the myeloma stage. For possible anemia and other low blood counts, blood tests are also used to assess kidney function, calcium levels and blood cell counts.