Evaluation of Blood Counts in Polycythemia Vera

Last updated: February 2024

Polycythemia vera (PV) is a rare, low-growing blood cancer in which bone marrow produces excess red blood cells. You can have it for years without having any symptoms. It is often discovered in routine blood tests. There is no known cause for the disease. Even though it is reflective of a genetic mutation, it is not an inherited condition.1

A type of myeloproliferative neoplasm blood cancer, polycythemia vera is characterized by a gene mutation that interferes with normal blood cell production. The Janus kinase 2 (JAK2) mutation causes cells to grow faster than normal in bone marrow. The condition generally develops in people over age 60 but can arise earlier.1-3

Symptoms of polycythemia vera

Common symptoms of polycythemia vera include:1-3

  • Itchiness, bleeding, and bruising
  • Headache and dizziness
  • Numbness, tingling, weakness, and fatigue
  • Fevers, blurry vision
  • Fullness or bloating in your left upper abdomen, which is a sign of an enlarged spleen

A diagnosis of polycythemia vera is made based on results from blood tests, genetic tests, and bone marrow analysis. Elevated hemoglobin, hematocrit, or blood cell counts can all be signs of polycythemia vera.1,2

Blood tests

A complete blood count (CBC) is a thorough cellular analysis of the blood. It measures numerous blood components including:2

  • Hemoglobin (Hgb) – An iron-rich protein that helps red blood cells carry oxygen throughout the body. The normal range for hemoglobin is 13.5 to 17.5 grams per deciliter for men and 12.0 to 15.5 grams per deciliter for women.
  • Hematocrit (Hct) – The proportion of red blood cells in a volume of blood, expressed as a percentage or an increase in hemoglobin concentration in the blood. Normal hematocrit concentration ranges from 36 to 46 percent in women and 42 to 52 percent in men.
  • Number of blood cells – A count of each type of cell present in the blood.
  • Blood smear – Looks at the number and shape of the red and white blood cells and platelets in the blood to see whether they appear normal.
  • Erythropoietin level (EPO) – A hormone made by the kidneys to stimulate bone marrow to make red blood cells. The normal range for EPO can vary from 3.7 to 36 international units per liter (IU/L). Unusually low levels can be caused by polycythemia vera.
  • Bone marrow tests – Check the bone marrow for red blood cell production to see if they develop and function normally.
  • Aspiration – A technique used to withdraw a sample of the liquid portion of bone marrow.
  • Biopsy – The surgical removal of a sample of solid bone marrow material.
  • Gene testing – Looks for the presence of the JAK2 gene mutation associated with polycythemia vera.

In polycythemia vera, there are too many red blood cells, and sometimes there are also too many platelets or white blood cells. The effect of this surplus of red blood cells can make the blood thicker. When blood doesn’t flow smoothly, it can cause clots to form. Clots can lead to stroke, heart attack, deep vein thrombosis, or pulmonary embolism.1-3

Nearly 30 percent of people experience blood clots before they have a PV diagnosis. In the 10 years after diagnosis, 40 to 60 percent of people with untreated PV could develop blood clots.1,3

Other complications can include an enlarged spleen. Although rare, when left untreated, PV can develop into other blood disorders including myelofibrosis, myelodysplastic syndrome, and leukemia.1,3

Treatments to address polycythemia vera

While PV has no cure, there are treatments that can diminish symptoms and lessen the risk of developing complications. Treatments are aimed at reducing both the amount of blood cells and overall volume. These include:1,2

  • Phlebotomy, or taking blood out of your veins, just like when donors give blood
  • Low-dose aspirin taken to reduce the risk of blood clots
  • Medications to block bone marrow from producing new blood cells
  • Exercise to improve blood flow and circulation

Under a doctor’s care, many people with polycythemia vera can lead a relatively normal life.

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