Blood and Urine Tests

Core Conclusion

Monitoring serum M-protein, 24-hour urine electrophoresis, and serum free light chains (sFLC, ratio 0.26 to 1.65) provides quantitative tracking of myeloma burden, where a 50% drop indicates partial response and 90% confirms VGPR.

Detailed Points

(1) SPEP and UPEP (Hunting for the "M-Protein") Myeloma cells are abnormal plasma cells that produce a useless, defective antibody known as a monoclonal protein, or M-protein.

• SPEP (Serum Protein Electrophoresis): This blood test acts like a scanner, using an electrical current to separate your proteins and calculate the exact amount of M-protein circulating in your blood (often called the "M-spike"). If your SPEP shows an M-protein level of >= 10$ g/L, it is typically considered measurable disease.
• UPEP (Urine Protein Electrophoresis): Sometimes, smaller fragments of this protein escape into your urine. This test requires you to collect your urine over a 24-hour period to measure these proteins (also called Bence Jones proteins). Having a urine M-protein level of >= 200$ mg per 24 hours is also an indicator of measurable disease. By regularly checking your SPEP and UPEP levels, your doctor can easily see if the M-protein is dropping, which means your treatment is working beautifully.

(2) The Importance of the Serum Free Light Chain (sFLC) Assay Antibodies are made of "heavy chains" and smaller "light chains" (known as kappa or lambda).

• Why it matters: About 15% of patients have "light chain myeloma," where their cancer cells only produce these smaller light chain fragments. These fragments are often missed by a standard SPEP test but can be highly toxic to the kidneys.
• What the numbers mean: A healthy person has a perfectly balanced ratio of kappa to lambda light chains (normally between 0.26 to 1.65). If the ratio of involved-to-uninvolved light chains is extremely abnormal at >= 100$ (with the involved light chain being >= 100$ mg/L), it is considered a major myeloma-defining event indicating highly active disease.

(3) CBC and CMP (Checking Your Organ Function) While M-protein tests track the cancer, the CBC and CMP track how the rest of your body is holding up.

• CBC (Complete Blood Count): This test measures your red blood cells, white blood cells, and platelets. Myeloma cells can crowd the bone marrow, preventing healthy cells from growing. Doctors look for anemia (a low hemoglobin value of $< 10$ g/dL, compared to normal ranges of 12.1 to 15.1 g/dL for women and 13.8 to 17.2 g/dL for men). They also monitor your white blood cells (like neutrophils) to ensure you are not at a high risk for infections.
• CMP (Comprehensive Metabolic Panel): This chemistry profile measures electrolytes and checks the health of your kidneys, liver, and bones. Key markers include:

  • Calcium: Normal is 8.5 to 10.2 mg/dL. A level of $> 11$ mg/dL indicates dangerous bone breakdown (hypercalcemia).
  • Creatinine: Normal is 0.6 to 1.3 mg/dL. A level of $> 2$ mg/dL is a warning sign of kidney impairment caused by the myeloma proteins.
  • Albumin: Normal is 3.4 to 5.4 g/dL. Lower levels can indicate poor nutrition or more advanced disease.

(4) Beta-2 Microglobulin (β2M) and Its Role in Staging

• What it is: β2M is a small protein found on the surface of myeloma cells. The normal range in your blood is 0.70 to 1.80 $\mu$g/mL. When the level is elevated, it acts as a tumor marker, reflecting a higher amount of cancer in the body.
• Staging: This simple test is a core part of the International Staging System (ISS). If your β2M is exceptionally low ($< 3.5$ mg/L) and your albumin is normal (>= 3.5$ g/dL), you are in Stage I, which has a very favorable prognosis. If your β2M is >= 5.5 mg/L, it places you in Stage III.
• Advanced Risk Understanding: Recent expert consensus guidelines have established that having a high β2M level (>= 5.5 mg/L) specifically while maintaining normal kidney function (creatinine < 1.2 mg/dL) is an independent marker for high-risk myeloma. This helps your doctor know immediately if you might benefit from a stronger treatment approach.

The above content is sourced from the following references

• First Line Treatment of Newly Diagnosed Transplant Eligible Multiple Myeloma
• International Myeloma Society/International Myeloma Working Group Consensus Recommendations on the Definition of High-Risk Multiple Myeloma
• Multiple Myeloma Learn Your Labs
• NCCN Clinical Practice Guidelines in Oncology: Multiple Myeloma
• NCCN Guidelines for Patients® Multiple Myeloma
• Patient Handbook