How is MDS Diagnosed?

Diagnosing Myelodysplastic Syndrome (MDS) involves a series of tests, including blood tests, bone marrow tests, and imaging tests. Each of these tests provides crucial information that helps doctors confirm an MDS diagnosis and understand the specifics of the disease.

Blood Tests

1. Complete Blood Count (CBC) is a common blood test that measures the levels of red blood cells, white blood cells, and platelets. MDS often presents with abnormal blood counts, such as low red blood cells (anemia), low white blood cells (leukopenia), or low platelets (thrombocytopenia).
2. Peripheral Blood Smear: For this test, a blood sample is examined under a microscope to check for abnormalities in the shape, size, and appearance of the cells. In MDS, cells may appear misshapen or immature (blasts).
3. Cytogenetic Analysis looks for changes in the chromosomes of cells from blood samples. Certain chromosomal changes can indicate the presence of MDS.
4. Complete metabolic panel (CMP) is a test that measures the levels of electrolytes in the blood. It also looks at markers like BUN and creatinine to assess kidney function and markers like AST and ALT to assess liver function. High levels of any of these labs can indicate that the kidneys or liver are not functioning as well as they should. 

Bone Marrow Tests

If blood tests suggest MDS, a bone marrow examination is essential to confirm the diagnosis.

1. Bone Marrow Aspiration and Biopsy: These tests are performed to obtain samples of liquid bone marrow and a small piece of bone with marrow. The samples are examined for abnormal cells, such as excess blasts, which can indicate MDS. The aspiration is done with a hollow needle, usually from the hip bone, followed by a biopsy using a different needle to collect the bone and marrow sample.
2. Flow Cytometry: This test measures the amount of DNA in cells and identifies abnormal cells. It can differentiate between MDS cells and other types of cells, including leukemia cells.
3. Cytogenetic Analysis:Similar to the blood test, this analysis on bone marrow samples identifies chromosomal abnormalities, helping to predict the prognosis and guide treatment.
4. Immunohistochemistry:This test uses special antibodies to detect specific molecules on the surface of cells, helping to differentiate between different cell types.
5. Fluorescent In Situ Hybridization (FISH): uses special fluorescent dyes that only attach to specific parts of chromosomes. FISH can find most chromosomal changes (such as translocations); some changes are too small to be seen with regular 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 accurate and can provide results within a few  days, which is why this test is now used in many medical centers.
6. Next-generation sequencing (NGS): This test provides everything that the FISH test provides regarding translocations but also identifies genetic “signatures” or genes that are activated or inactivated, over- or under-expressed. This provides redundant information from the FISH test but looks at cells on a molecular level and looks for 35,000 genes in a single test. The abnormal cells are purified from a bone marrow biopsy sample, and the genetic material is extracted, providing valuable information about the subtype of MDS and allowing patients to receive personalized treatments.
7. Karyotyping: This technique evaluates the chromosomes (organized DNA package) in the bone marrow's abnormal cells. Chromosomes are extracted from the cells and lined up, then analyzed under a special microscope to look for abnormalities like translocations. Some MDS cells may have extra chromosomes, missing chromosomes, or other chromosomal abnormalities. Finding these changes can sometimes help predict prognosis and determine treatment options.

To confirm an MDS diagnosis, analyzing the bone marrow cells is required, and specially a type of cell called blast, which is an immature abnormal cell characteristic for MDS and AML (acute myeloid leukemia). The blast cell percentage that determines an MDS diagnosis is less than 20% in the bone marrow and less than 20% in the bloodstream. Doctors will. diagnose AML if the blast percentage is above 20% in the bone marrow or above 20% in the bloodstream. 

Other Biopsies

1. Fine needle aspiration (FNA) biopsy can be performed additionally if an imaging study shows a potential tumor or abnormality. This type of biopsy uses a very thin needle and an ordinary syringe to withdraw a small amount of tissue. If the biopsy needed is deep inside the body, the needle can be guided while it is viewed on a computed tomography (CT) scan. The main advantage of FNA is that it does not require surgery and can be useful in diagnosing cancers that have spread to nodes from other organs. The disadvantage is that, in some cases, the thin needle cannot remove enough tissue for a definite diagnosis. 
2. Core needle biopsy: This test is similar to a fine needle aspiration biopsy but a larger needle is used, and a larger tissue sample is removed.

Imaging Tests

1. Chest X-ray: A chest X-ray may be performed to check for infections or other conditions contributing to the patient’s symptoms.
2. Computed tomography (CT) scan (also known as a CAT scan) is an X-ray procedure that produces detailed cross-sectional images of the body. Instead of taking one picture, like a conventional X-ray, a CT scanner takes many pictures of the part of the body being studied as it rotates. A CT scan can show enlarged lymph nodes, a swollen spleen, or pockets of infection in your organs. Oftentimes, a patient will drink 1 to 2 pints of a contrast solution before the scan. This helps outline the intestine so that it is not mistaken for tumors. Patients may also receive an intravenous (IV) line through which a different contrast dye is injected. This helps better outline body structures. The injection can cause a feeling of warmth throughout the body, referred to as flushing. Some people are allergic to IV contrast and should tell their doctor if they have ever reacted to any X-ray contrast material in the past. CT scans take longer than regular X-rays and require lying motionless on a table while images are taken. Some patients might feel confined during the scan, but the tests are over relatively quickly. 
3. CT-guided needle biopsy is used to precisely insert a biopsy needle into a suspected tumor. For this procedure, the patient remains on the CT scanning table while a radiologist advances a biopsy needle toward the tumor's location. CT scans are repeated until the needle is within the mass. A fine needle biopsy sample or a core needle biopsy sample is removed and examined under a microscope.
4. Magnetic resonance imaging (MRI) scan helps determine if leukemia has spread to the brain or spinal cord by producing cross-sectional slices of the body like a CT scanner and producing slices parallel to the body's length. MRI uses radio waves and strong magnets instead of X-rays. The energy from the radio waves is absorbed and then released in a pattern formed by the type of tissue and by certain diseases. A computer translates the pattern of radio waves given off by the tissues into a very detailed image of the body. A dye can be injected as with CT scans but is used less often. MRI scans are a little more uncomfortable than CT scans. They can take an hour or longer, and the patient is placed inside tunnel-like equipment, which can feel confining. The machine makes a thumping noise, but the facility can provide headphones with music to block out the sound.
5. Positron emission tomography (PET) scan uses a radioactive glucose injection into the patient’s vein to look for cancer cells. Because cancers use glucose (sugar) at a higher rate than normal tissues, the radioactivity will tend to concentrate on the cancer. A scanner is used to spot radioactive deposits.

MDS diagnosis is a multi-step process involving blood tests, bone marrow tests, and imaging studies. The specific tests used may vary depending on the patient’s symptoms and the type and severity of MDS suspected. Not all patients will require every test mentioned, but together, these tests provide a comprehensive picture that guides diagnosis and treatment.

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