Doctors use many tests to diagnose MDS. Some tests may also determine which treatments may be the most effective. Your doctor may consider these factors when choosing a diagnostic test:

• Age and medical condition
• Type of disease suspected
• Severity of symptoms
• Previous test results

In addition to a physical examination, the following tests may be used to diagnose MDS:

Blood tests [2]. A complete blood count (CBC) test measures the numbers of red blood cells, white blood cells, and platelets.

Peripheral (circulating) blood smears. A drop of blood is placed on a slide, smeared into a thin film, and placed under a microscope for examination. The percentages of the different types of cells are counted, and cell morphology (the appearance of cells under the microscope) is looked at to find out if or how the cells are different from healthy cells. 

Bone marrow biopsy and aspiration [3]. These two procedures are similar and often done at the same time. Bone marrow has both a solid and liquid part. A bone marrow biopsy is the removal of a small amount of solid tissue using a needle. An aspiration removes a sample of fluid with a needle. The samples are then analyzed by a pathologist (a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease) to determine the percentage of red blood cells, white blood cells, platelets, and blasts. A common site for the bone marrow biopsy and aspiration is the pelvic bone, which is located in the lower back by the hip. The skin in that area is numbed with medication beforehand, and other types of anesthesia (medication to block the awareness of pain) may be used. The appearance of the bone marrow tissue, along with blood cell counts and chromosomal analysis (see below), is needed to confirm a diagnosis of MDS.

Cytogenetic (chromosomal) analysis. Looking at the chromosomes of the cells in the blood and bone marrow shows specific abnormalities that help doctors tell the difference between MDS and other blood disorders. About 50% of people with MDS have one or more chromosomal abnormalities, regardless of the subtype [4]. Primary MDS often has one chromosomal abnormality. Secondary MDS often has many or complex chromosomal changes. The most common abnormalities affect chromosomes 5, 7, 8, 11, 12, and 20.

Immunophenotyping. Immunophenotyping is the examination of antigens, a specific type of protein, on the surface of the MDS cells. Immunophenotyping allows the doctor to confirm the exact type of MDS.

Learn more about what to expect when having common tests, procedures, and scans. [5]

After these diagnostic tests are done, your doctor will review all of the results with you. If the diagnosis is MDS, these results also help the doctor describe the disease. Learn more about the first steps to take after a diagnosis [6].