Complete blood count (CBC) and differential
CBCs and differentials are the most frequently ordered tests used to help diagnose and monitor MPDs. Often ordered as part of a yearly physical exam, they are routine tests that count the number and relative proportion of each of the different types of cells in your blood stream. They give your doctor information about the size, shape, and relative maturity of the blood cells present in your blood at that moment.
CBCs and differentials can be used to detect WBC, RBC, and platelet increases, decreases, and abnormalities. They can help determine their severity, diagnose their cause, monitor the course of a disease, and monitor the response to treatment.
With polycythemia vera, increased RBCs, platelets, and sometimes WBCs, may be seen. With myelofibrosis, immature granulocytes and misshapen immature teardrop-shaped red blood cells are often seen, and WBC and RBC numbers are often decreased. With thrombocythemia, greatly increased numbers of platelets are seen along with abnormally large platelets, platelet clumps, and fragments of megakaryocytes.
Irregularities in cell counts may be due to MPDs, but they may also be due to a variety of other temporary or chronic conditions. Other testing is usually done to confirm or rule out the diagnosis of an MPD.
Bone marrow aspiration/biopsy
If a doctor suspects a bone marrow disorder, he may order a bone marrow aspiration or biopsy to collect a small sample of marrow. When a specialist (a pathologist, oncologist, or hematologist) examines the bone and fluid from the bone marrow sample under the microscope, he can see the number, size, and shape of precursor cells (blasts), red and white blood cells, and megakaryocytes (platelet precursors). He can determine the proportions of mature and immature cells, see any overgrowth of fibrous tissue, and detect any cancer cells from cancers that may have spread to the marrow. Most bone marrow disorders can be diagnosed during this examination.
For more detail on this test, see Bone Marrow Aspiration and Biopsy.
Other testing that is sometimes done includes:
ABGs (Arterial blood gases) - This test measures the amount of gases in your arterial blood and may be done when polycythemia vera is suspected. Low levels of oxygen are associated with secondary polycythemia.
Erythropoietin is a hormone that stimulates the bone marrow to produce RBCs. With primary polycythemia, erythropoietin levels will be very low or absent, but with secondary polycythemia they will be normal or high.
Genetic testing is sometimes used in suspected chronic myelogenous leukemia to check for the presence or absence of a Philadelphia (Ph') chromosome or a bcr-abl translocation (see BCR ABL) and in suspected polycythemia vera, myelofibrosis, and essential thrombocythemia for the presence or absence of JAK2 mutations, a gene associated with marrow cell production.
X-rays and other imaging scans are sometimes used to look for signs of disease such as masses of cells in the chest, spleen, or liver.