How Is Polycythemia Vera Diagnosed?
You may have polycythemia vera (PV) before signs or
symptoms appear. Many times, doctors discover their patients have PV through
routine blood tests performed for other reasons. If you have no clear symptoms
for PV, but show higher than normal levels of hemoglobin and hematocrit
(he-MAT-o-krit) in your blood test, your doctor may want to do more tests.
Doctors diagnose PV based on symptoms, physical
exam, age, test results, and overall health, including other chronic diseases.
The doctor will find out as much as possible about your medical history. Your
doctor will look for signs of polycythemia during your physical exam, including
enlargement of the spleen, reddened skin on the face, and bleeding from the
gums. If your doctor confirms that you have polycythemia, the next step is to
determine if you have PV or secondary polycythemia.
Often, your medical history and physical exam can
confirm which type of polycythemia you have. If not, your doctor may order
tests that check the level of erythropoietin (EPO) in your blood. Patients with
PV have extremely low levels of EPO. Patients with normal to high levels of EPO
in their blood more than likely suffer from secondary polycythemia.
Specialists Involved
If your primary care doctor suspects you have PV,
you may be referred to a hematologist (a doctor who is an expert in treating
blood conditions).
Diagnostic Tests and Procedures
The doctor treating you may order a number of
different blood tests to diagnose PV. These tests include a complete blood
count (CBC), conducted along with other tests if necessary.
- The CBC counts the numbers of all three types of
blood cells-red blood cells that carry oxygen, white blood cells that fight
infection, and platelets that help clot the blood. If your CBC shows higher
than normal counts of these cells, especially the red blood cells, you may have
PV.
- The CBC also measures hemoglobin, the iron-rich
protein in red blood cells that carries oxygen through the body. A higher than
normal hemoglobin level may be a sign that you have PV.
- The hematocrit part of the CBC measures the
percentage of blood that consists of red blood cells. A higher than normal
hematocrit level may be a sign that you have PV.
Your doctor may order additional blood tests to
confirm a diagnosis of PV:
- A blood smear-A sample of your blood is viewed
under a microscope to collect information about the number and shape of blood
cells. Your doctor will examine the smear for the high concentration of red
blood cells seen in PV and for abnormal types of blood cells that are seen in
myelofibrosis and other conditions related to PV.
- Arterial blood gas test-A sample of your blood is
taken from an artery to measure the amount of oxygen, carbon dioxide, and pH
(acidity) in the blood. If your test results show a lower than normal level of
oxygen in your blood, it may be a sign you have PV.
- EPO level-Your blood is tested to measure the
level of EPO, a hormone that stimulates bone marrow to produce new blood cells.
If you have PV, this test result will show lower than normal levels of EPO in
your blood.
- Red blood cell mass-This test usually takes place
in a hospital in the nuclear medicine department. The health professional
performing the test takes a sample of your blood. A very weak radioactive dye
is mixed with your blood sample. The weak dye attaches itself to the red blood
cells and plasma in your sample. The tagged cells in your sample are injected
back into your bloodstream and spread quickly throughout your body. By taking
another sample of your blood, or using special cameras sensitive to the dye,
technicians can figure out the total number of red blood cells in your body.
Higher than normal red blood cell counts may be a sign you have PV.
In some cases, your doctor may want to do a bone
marrow biopsy or aspiration. A bone marrow biopsy is a minor surgical procedure
your doctor performs to remove a small amount of bone marrow tissue with a
needle from your body. In a bone marrow aspiration, your doctor removes a small
amount of bone marrow fluid through a needle. Bone marrow biopsy or aspiration
tests whether your bone marrow is healthy and producing a normal amount of
blood cells. If the test shows that your bone marrow is producing higher than
normal amounts of blood cells, it may be a sign you have PV. |