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Staging provides information regarding the extent of the disease, which helps to determine appropriate therapy as well as prognosis. The most commonly used system for staging multiple myeloma (MM) is called the Durie-Salmon staging system which synthesizes information regarding blood counts (hemoglobin levels), serum calcium level, kidney function, immunoglobulin levels (IgG value and IgA value) and the presence or absence of bone lesions to classify the disease into stage I, II or III. The higher the classification number, the more advanced the extent of multiple myeloma.

Durie-Salmon Staging Classification System

The Durie-Salmon Staging Classification System, developed in 1975, classifies patients with multiple myeloma into the following three stages:

Stage I

This is the earliest stage of multiple myeloma and is characterized by the following:

• No sign of anemia (hemoglobin values are normal; greater than 10 g/dL)
• No sign of hypercalcemia (serum calcium values are normal; less than 12 mg/dL)
• X rays of bone are normal or exhibit only a single bone plasmacytoma
• Low M protein production rates:
  • IgG value is less than 5 g/dL
  • IgA value is less than 3 g/dL
  • Bence-Jones protein (free immunoglobulin light chains in urine) as measured by protein electrophoresis is less than 4g/24h

Stage II

This is an intermediate stage of multiple myeloma. It is more advanced than Stage I but not as advanced as Stage III.

Stage III

This is an advanced stage of multiple myeloma. Stage III classification is assigned if one or more of the following criteria are present

• Anemia (hemoglobin value is less than 8.5 g/dL)
• Hypercalcemia (serum calcium value greater than 12 mg/dL)
• X-rays reveal multiple bone lesions
• High M protein production rates:
  • IgG value is greater than 7 g/dL
  • IgA value is greater than 5 g/dL
  • Bence-Jones protein is greater than 12g/24h

The three stages of the Durie-Salmon classification system are combined with the results of kidney function tests that measure serum creatinine levels to provide a more accurate evaluation of the extent (stage) of the multiple myeloma (MM). Creatinine is a blood protein that is usually filtered-out of the body by the kidneys. Creatinine is an indicator of how well the kidneys are functioning.

Patients with multiple myeloma are subclassified into either "A" or "B" categories based on serum creatinine levels:

• "A" - normal kidney function (serum creatinine value is less than 2.0 mg/dL)
• "B" - abnormal kidney function (serum creatinine value > 2.0 mg/dL)

International Staging System for Multiple Myeloma

More recently, a newer staging system for multiple myeloma, called the International Staging System (ISS), has been developed. The ISS classifies patients with multiple myeloma into 3 Stages (I, II, or III) based strictly on the levels of two substances in the bloodstream: beta-2 microglobulin and albumin. Research has demonstrated that, together, these two "markers" are very sensitive for determining the extent of the disease and are also useful for predicting survival. The 3 Stages of the ISS classication system are: