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by Lynne Lederman, PhD
Dr. Griepp discussed the establishment of the International Staging System (ISS) for myeloma. The system classifies myeloma into three stages based on serum beta-2-microglobulin and albumin levels. The stages correlate with risk and survival. Serum albumin may be measured by protein electrophoresis (PEL) or by chemical tests. M-spikes, especially over 25 g/L, appear to increase albumin levels measured by PEL, whereas chemical tests (e.g., bromcresol green or bromcresol purple) measure albumin and other proteins such as gamma globulin, but is not affected by an M-spike; results can be adjusted to compensate. Other methods for albumin measurement include immunonephelometry, the gold standard for measurement in cerebral spinal fluid, and capillary zone electrophoresis (CZE), which may be used more in the future. However, overall, differences in measurement and therefore staging had no impact on survival curves in a study of a large group of patients. The use of PEL may avoid having to do an additional test. Either PEL or chemical methods of determining serum albumin levels may be used for staging, and publications of trial results should specify which method was used. Dr. Barlogie commented that clinicians should be consistent with the type of test used for individual patients and within a clinical trial.