Blood tests and a bone marrow test are used to diagnose myelofibrosis (MF). Your doctor may suspect MF as a result of a routine physical exam showing an abnormal blood test or an enlarged spleen.
After your doctor takes your blood, he or she sends it to a lab for a complete blood count (CBC), which measures the number of red cells, white cells and platelets in your blood. Blood cell counts vary among patients diagnosed with MF. Your doctor may consider an MF diagnosis if your results show:
- a decrease below the normal range in red cells (anemia)
- an increase above the normal range in white cells
- an increase above the normal range in platelet counts (seen in about one-third of patients)
- a mild to moderate decrease below the normal range in platelet counts (seen in about one-third of patients)
Your blood cell counts may vary during the disease's course. Some patients have very little change in certain blood counts. For example, a patient may have no elevation in the white cell or platelet counts. Other patients may have lower than normal the numbers of white cells or platelets instead of the more common finding of higher than normal numbers.
Blood tests may also show abnormal levels of other substances:
- giant platelets, abnormal platelet formation and circulating dwarf megakaryocytes
- elevated serum levels of uric acid, lactic dehydrogenase (LDH), alkaline phosphatase and bilirubin
- decreased serum levels of albumin, total cholesterol and high density lipoprotein (HDL), the "good" cholesterol
Bone Marrow Tests
Your doctor tests your bone marrow to help confirm a diagnosis. An MF patient's marrow will reveal either some or a great deal of fibrosis (scarring).
Bone marrow testing involves two steps usually performed at the same time in a doctor's office or a hospital:
- a bone marrow aspiration to remove a liquid marrow sample
- a bone marrow biopsy to remove a small amount of bone filled with marrow
Your blood or bone marrow sample may be used for a lab test called a karyotype. A hematopathologist examines the size, shape and number of your chromosomes in a sampling of cells under a microscope. The karyotype results may be helpful in making certain treatment decisions.
A blood cell analysis for the JAK2 gene mutation may help in diagnosing MF, although the mutation is found in only about half of all patients.