Protein Testing in Lymphoproliferative Disorders
Serum protein electrophoresis with or without certain additional tests is required on all new patients with multiple myeloma or other plasma cell disorders, malignant lymphoma and all patients with chronic B or T lymphoid leukemias. These tests are not required in new patients with a diagnosis of Hodgkin's disease. The terminology of protein testing and recommendations for specific tests are as follows:
1. Serum Protein Electrophoresis (SPE)
SPE is performed by cellulose acetate or high resolution agarose gel electrophoresis. The latter technique is very sensitive and useful for the detection of small monoclonal paraprotein bands. In the majority of patients with myeloma, SPE is useful for diagnosis usually demonstrating a monoclonal protein, associated hypogammaglobulinemia or both. For long-term monitoring of patients with clinically significant monoclonal proteins, quantitation of the paraprotein by SPE is preferred to other available tests. It more accurately estimates the actual amount of protein present than quantitative immunoglobulin studies.
2. Immunofixation (IFE)
Once a paraprotein band is identified by SPE, the type of the paraprotein band is determined by IFE. This technique is very sensitive and has, for the most part, replaced immunoelectrophoresis. In any disorder characterized by a paraprotein, this test is usually only required at diagnosis to establish the nature of the paraprotein. If a monoclonal protein is identified in the urine (Bence-Jones protein) by urine protein electrophoresis (UPE), the identity of the paraprotein is also determined by IFE.
3. Quantitative Immunoglobulin Levels
The specific amounts of individual immunoglobulins by class (IgG, IgM, IgA) can be determined by several methodologies. Two of the more common methods are radial immune diffuse and nephelometry. These measurements are of utility in patients with immune deficiency, however, they are of minimal value in patients with neoplastic lymphoproliferative disorders with a paraprotein. Occasionally it is useful to determine that the other classes of immunoglobulin are decreased in a patient with a paraprotein.
4. Urine-Protein Electrophoresis (upe)
A 24 hour urine sample is usually required in patients with a neoplastic paraprotein. The urine sample is concentrated and then fractionated by protein electrophoresis. The amount of protein is quantitated and the pattern is examined to determine if a paraprotein band is present. If a band is detected the specific type is identified by IFE. Older qualitative tests for presence of Bence-Jones protein are no longer useful.