Complete blood count (CBC) and differential
CBCs and differentials are the most frequently ordered tests used to help diagnose and monitor MPNs. 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 a blood sample. They also provide information about the size, shape, and relative maturity of the blood cells present in a person's 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, misshapen teardrop-shaped red blood cells, and immature nucleated 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 or giant platelets amd platelet clumps.
Irregularities in cell counts may be due to MPNs, 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 MPN.
Bone marrow aspiration/biopsy
If a bone marrow disorder is suspected, a doctor 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 portion of the bone marrow sample under the microscope, the type, number and appearance of various cells can be assessed and, if present, overgrowth of certain types of cells, fibrosis, and tumors can be determined. Most bone marrow disorders can be revealed during this examination, but further testing may be necessary to confirm a diagnosis.
Other tests that sometimes are ordered include:
- Arterial blood gases (ABGs). This test measures the amount of gases in the 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.
- Cytogenetic analysis and molecular testing may be used to help diagnose suspected MPNs. For example, genetic testing is 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). If polycythemia vera, primary myelofibrosis, or essential thrombocythemia is suspected, a doctor may order a test to check for JAK2 mutation (see JAK2) or MPL mutation.
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.