Blood tests are done routinely at the time of diagnosis and throughout the disease course to assess response to treatment and side effects and to monitor for 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), and low platelet count (thrombocytopenia).
Complete Blood Count (CBC)
The CBC is both a basic test done during every medical check-up and one of the most important blood tests used for diagnosing and monitoring myeloma patients. Many cases of MM — and its asymptomatic predecessors, monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM) — are identified as the result of blood tests routinely ordered as part of an annual medical exam, such as the CBC.
The CBC quantifies all the cells that make up the solid parts of blood. (The liquid part of blood, in which the blood cells are suspended, is colorless, and is called serum.) All of your blood cells —red blood cells (RBC), white blood cells (WBC), and blood-clotting cells called platelets (PLT) — are made in the bone marrow, which is where myeloma grows. Both multiple myeloma itself, as well as its many treatments, affect the ability of new blood cells to grow in the bone marrow.
Your CBC will be watched carefully throughout your treatment course to make sure that 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, and PLT, with subcategories under RBC and WBC. To learn more about these blood cell types and subcategories, visit the Understanding Your Test Results booklet, pp. 7–11.