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If you are showing signs or symptoms of MDS, your doctor will likely order a series of blood tests to confirm an MDS diagnosis.

Complete Blood Count (CBC)

CBC is a blood test from a blood draw that will allow your doctor to look at your blood cell counts for your red blood cells, white blood cells and platelets. Often in MDS patients, anemia (low red blood cell count) is present. White blood cell and platelet counts may be low as well (called neutropenia and thrombocytopenia, respectively). 

Doctors may do a blood smear, where a small blood sample is put on a slide and looked at under a microscope. In some MDS patients, an excess of blasts may be present in the blood. Blasts are immature stem cells. An excess of blasts in the blood sample can be a sign of a bone marrow disorder. A blood smear also allows a doctor to look at the appearance of blood cells. In an MDS patient, blood cells may appear misshapen or the wrong size. 

Low blood counts can be a result of many different health conditions. Doctors will often look for other causes of low blood counts through other tests run on your blood sample. If any other cause of low blood count is identified, the symptoms will be explained and they will be less likely to move onto any bone marrow testing.

Bone Marrow Tests

These blood tests may lead a doctor towards an MDS diagnosis, but the diagnosis cannot be made until a doctor has completed an examination of the patient's bone marrow.

Two tests of the bone marrow are typically performed when MDS is suspected, a bone marrow biopsy and a bone marrow aspiration. You will be given a local anesthetic at the procedure site. If you prefer, the procedure can be done under light anesthesia called conscious sedation. It makes you tired for an hour or two but doesn’t knock you out. Many patients prefer to go without any pain medication. There is no “wrong” decision.

Bone Marrow Aspiration 

These are usually performed one after the other with the aspiration first. For this procedure, a  hollow needle is inserted into the back of the pelvic bone (hip) after a local anesthetic is applied to the area. While the area is numbed, this may still cause a brief short pain. The hollow needle will allow the doctor to collect a sample of just the liquid bone marrow.

Bone Marrow Biopsy

After the aspiration, a different needle is inserted to collect a tiny sliver of bone and marrow together, about 1/16-inch across and 1-inch long. This is done right after the aspiration while the area is still numbed. You may experience soreness at the procedure site once the anesthetic wears off. 

Bone Marrow Test Results

The aspiration and biopsy will be examined by a pathologist and most likely a hematologist as well. Similar to the CBC, doctors will be looking for abnormalities in the bone marrow content and the appearance of the cells. This could look like misshapen cells or an excess of blasts. 

Excess blasts (which are immature stem cells) and not enough mature cells is what can lead to a low blood count. These blasts can crowd up the bone marrow and are a source of the bone pain some patients feel. If a patient has under 20% blasts they may be given an MDS diagnosis. Over 20% blasts leads doctors towards an AML diagnosis. 

Further Testing

Further testing may be ordered by your doctor to determine MDS type or severity. 


In this test, a part of the bone marrow biopsy sample is treated with special antibodies (man-made versions of immune system proteins) that attach only to specific molecules on the cell surface. These antibodies cause color changes, which can be seen under a microscope. This test may be helpful in differentiating between cell types and in finding MDS cells.

Flow Cytometry

Like immunohistochemistry, this test looks for certain substances on the outside surface of cells that help identify what types of cells they are. This test is able to look at many more cells than immunohistochemistry.

For this test, a sample of cells is treated with special antibodies that stick to the cells only if certain substances are present on their surfaces. The cells are then passed in front of a laser beam. If the cells now have antibodies attached to them, the laser will cause them to give off light, which can be measured and analyzed by a computer. Groups of cells can be separated and counted by these methods.

This is the most commonly used test for immunophenotyping, the process of classifying cells according to the substances (antigens) on their surfaces. Different cells and cell types have different antigens on their surface. These antigens may also change as each cell matures.

Flow cytometry can help determine if there are abnormal cells in the bone marrow and if they are leukemia cells, MDS cells, lymphoma cells, some other cancer, or a non-cancerous disease.


This technique allows doctors to evaluate the chromosomes (long strands of DNA) in normal bone marrow cells and blast cells. The cells are examined under a microscope to see if the chromosomes have any abnormalities such as a translocation. Translocations occur when part of one chromosome has broken off and becomes attached to another chromosome. This can happen in some cases of MDS. Some MDS cells may have too many chromosomes, too few chromosomes, or other chromosome abnormalities. Finding these changes can sometimes help predict prognosis and determine treatment options.

Cytogenetic testing usually takes about 1 to 2 weeks because the cells must grow in lab dishes for a couple of weeks before their chromosomes are ready to be viewed under the microscope.

Fluorescent In Situ Hybridization (FISH Analysis)

Fluorescent in situ hybridization (FISH) is similar to cytogenetic testing. It uses special fluorescent dyes that only attach to specific parts of chromosomes. FISH can find most chromosome changes (such as translocations) that can be seen under a microscope in standard cytogenetic tests, as well as some changes too small to be seen with usual cytogenetic testing.

FISH can be used to look for specific changes in chromosomes. It can be used on regular blood or bone marrow samples. It is very accurate and can usually provide results within a couple of days, which is why this test is now used in many medical centers.


This is a comprehensive review of various tests and procedures patients with suspected MDS are known to receive. It is important to note that a diagnostic work-up for MDS may look different among patients. Not all patients require each and every one of the tests mentioned above. MDS is a variable disease and diagnosis depends on the doctor's training, what type of MDS the patient is likely to have and the severity of their MDS.


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