Which is the most definitive test to confirm a diagnosis of multiple myeloma

Blood tests are routinely done at the time of diagnosis and throughout the disease course. These tests assess:

  • response to treatment
  • side effects
  • signs of possible relapse

The complete blood count (CBC) assesses

  • the presence or absence of low red blood cell count (anemia)
  • low white blood cell count (leukopenia)
  • low platelet count (thrombocytopenia)

Complete Blood Count (CBC)

The CBC is both a basic test done during every medical check-up. It is one of the most important blood tests used for diagnosing and monitoring myeloma patients. 
A routine blood test may identify a case of

  • multiple myeloma
  • smoldering multiple myeloma
  • monoclonal gammopathy of undetermined significance (MGUS)

The CBC quantifies all the cells that make up the solid parts of blood. The liquid part of blood that is colorless is called serum.  Blood cells are suspended in the serum.
Red blood cells (RBC), white blood cells (WBC), and blood-clotting cells called platelets (PLT) are all made in the bone marrow. Myeloma grows in the bone marrow. Both multiple myeloma itself, as well as its many treatments, affect the ability of new blood cells to grow in the bone marrow.

Your healthcare team will observe your CBC throughout your treatment course. They will ensure your blood cell counts are not decreasing to dangerous levels. Sometimes patients must have a CBC every week to make sure that a particular treatment is not taking a toll on one or more of the blood cell types.

CBC results are broken down into the major headings of

  • RBC
  • WBC
  • PLT, with subcategories under RBC and WBC.

Learn more about these blood cell types and subcategories, visit the Understanding Your Test Results booklet, pp. 7–11.

What's Next?

What tests do you need to assess your kidney function?

All myeloma patients should have tests that monitor your disease and kidney function.

Related Content

Understanding Your Test Results


The International Myeloma Foundation medical and editorial content team

Comprised of leading medical researchers, hematologists, oncologists, oncology-certified nurses, medical editors, and medical journalists, our team has extensive knowledge of the multiple myeloma treatment and care landscape. Additionally, Dr. Brian G.M. Durie reviews and approves all medical content on this website. 

At the Jerome Lipper Multiple Myeloma Center and LeBow Institute for Myeloma Therapeutics at Dana-Farber Brigham Cancer Center, the oncologists who lead your treatment team work closely with hematopathologists to diagnose your condition and guide your treatment. These individuals have expertise in evaluating test results and genetic findings.

The diagnostic evaluation includes a review of your medical history, a physical exam, and the tests described below. We carry out this evaluation as quickly as possible, particularly if we believe there is an urgent need for you to start treatment.

Bone marrow biopsy

  • This test is required to confirm the diagnosis of multiple myeloma. A needle is inserted into the bone marrow space to remove a small sliver of bone marrow.
  • Our hematopathologists examine the tissue under a microscope to determine if there are myeloma cells in the bone marrow.
  • Genetic studies, including metaphase cytogenetics and fluorescence in situ hybridization, are performed on the bone marrow sample to identify gene changes that have occurred in the myeloma cells. We have the capacity to perform more specialized assessments of gene changes as well, and can discuss these with you at the time of your visit.
  • Bone marrow biopsies are also performed intermittently after the initial diagnostic study, although we try to limit how often they are done.

Blood tests

You will have lab tests that include comprehensive blood chemistries, complete blood count, serum and urine protein electrophoresis, the serum free light chain assay, and beta2 microglobulin. These tests allow us to evaluate the function of organs, such as the kidney, liver, and bone marrow, and to assess the status of your multiple myeloma at regular intervals.

The serum or urine protein electrophoresis identifies the presence, type, and concentration of the M-protein, or monoclonal protein. It also provides a measure of the concentration of the major immunoglobulin types in the blood, including IgG, IgA, and IgM.

The serum free light chain assay provides the concentration of the two light chains that are found in the body — the kappa and lambda light chains — and the ratio between these light chains. People with multiple myeloma typically have abnormally high levels of either kappa or lambda light chain, and an abnormal ratio between the two light chains.

Radiographic studies

You will have imaging studies to evaluate for bone or other abnormalities. These studies could include X-rays, MRI, CT, and/or PET-CT imaging.


Staging in multiple myeloma has traditionally been done using the Durie Salmon staging system and the International Staging system. The Durie Salmon staging system provides insight regarding the overall amount of disease at time of diagnosis, while the International Staging System, which is based on the concentration of albumin and beta2 microglobulin at time of initial diagnosis, provides insight on prognosis.

It is important to note that no staging system is perfect and that patients with advanced stage disease can do very well over time with appropriate therapy.

Which is the most definitive test to confirm multiple myeloma?

Bone marrow biopsy.
This test is required to confirm the diagnosis of multiple myeloma. ... .
Our hematopathologists examine the tissue under a microscope to determine if there are myeloma cells in the bone marrow..

What tests are done to diagnose multiple myeloma?

Tests to Find Multiple Myeloma.
Blood counts. The complete blood count (CBC) is a test that measures the levels of red cells, white cells, and platelets in the blood. ... .
Blood chemistry tests. ... .
Urine tests. ... .
Quantitative immunoglobulins. ... .
Electrophoresis. ... .
Serum free light chains. ... .
Beta-2 microglobulin. ... .
Bone marrow biopsy..

What is the gold standard in diagnosing multiple myeloma?

Plain radiography remains the gold standard imaging procedure for staging newly diagnosed and relapsed myeloma, according to an International Myeloma Working Group consensus statement.

What is a major criterion for the diagnosis of multiple myeloma?

The diagnosis of MM requires 10% or more clonal plasma cells on bone marrow examination or a biopsy-proven plasmacytoma plus the presence of one or more myeloma-defining events. Myeloma-defining events include the presence of one or more CRAB features, or one or more biomarkers of malignancy.