Polycythemia vera (PV) diagnosis

There are several different blood tests used to determine PV:  

Complete blood count (CBC) with differential 

This test measures the number of red blood cells, white blood cells, and platelets in a sample of blood. It also measures the amount of the iron-rich protein that carries oxygen in red blood cells and the percentage of whole blood made up of red blood cells (the hematocrit). People with PV have high red blood cell counts.   

They also often have: 

• Increased hemoglobin levels
• Increased hematocrit levels
• Increased white blood cells and platelets 

Red cell mass test   

This procedure is used to measure the volume (amount) of red blood cells in relation to the volume of plasma (fluid) in whole blood. In patients with PV, there may be an absolute increase in red blood cell mass. This test is infrequently performed in the United States due to high cost, difficulty obtaining the appropriate test materials, and the advent of new blood tests such as molecular tests.  

Blood chemistry profile

This blood test measures the levels of certain substances released into the blood by organs and tissues in the body. These substances include electrolytes (such as sodium, potassium and chloride), fats, proteins, glucose (blood sugar), uric acid, and enzymes. 

The test findings indicate how well a person’s kidneys, liver, and other organs are working. Although this test is not used to diagnose PV, if the results show that there is an abnormal amount of a particular substance in the blood, it may be a sign of disease or some other health problem. 

Blood clotting tests 

Patients with very high platelet counts may be tested for acquired von Willebrand disease, a blood disorder that can impair normal blood clotting and cause major bleeding. Blood contains many proteins that help the body stop bleeding, one of which is known as von Willebrand factor. High platelet counts can limit how well the von Willebrand proteins clot. Several blood clotting tests are used to diagnose von Willebrand disease.  

Erythropoietin (EPO) level 

This test measures the level of EPO in the blood. EPO is a hormone mainly made in the kidneys to stimulate the production of new red blood cells. In people with PV, high red blood cell counts can suppress EPO levels. Results of EPO tests can be used to help diagnose PV. 

Learn more about blood tests.

These tests look for abnormal changes in the genes, chromosomes, proteins, or other molecules within the patient’s cancer cells. They are used for diagnosis and treatment planning.  

Polymerase chain reaction (PCR)  

This is a very sensitive test used to detect and measure specific genetic mutations that are too small to be seen with a microscope. PCR testing basically amplifies (increases) small amounts of specific pieces of DNA so that they are easier to detect and measure in a cell sample. It looks for the presence or absence of specific gene mutations. PCR testing can be done with blood or bone marrow samples. 

Next-generation sequencing (NGS)  

Next-generation sequencing, also called “molecular testing” or “genomic testing,” refers to a number of different laboratory tests that examine the exact sequence (order) of DNA or RNA. This makes it possible to identify a variety of genetic changes in a patient’s cancer cells.  

These changes are important in guiding risk assessment and prognosis and may also inform treatment decisions for targeted therapy specific to the particular change in the genetic sequence of the cancer cell.  

The information these tests provide can help doctors to determine which patients are at high risk and may need more intensive treatment or may benefit from treatment with new therapies.  

There are targeted sequencing tests (also called “multigene panels”) that look for specific mutations in the cancer cells. These tests focus on specific sets of genes or areas of DNA.  

There are also broad DNA sequencing tests (genomic screening tests) that analyze the sequence of large regions of DNA, rather than looking for mutations of specific genes. Doctors may also order sequencing of all the DNA in the cancer cells, and/or normal cells in the body. This test is known as “whole genome sequencing.”  

The term “next-generation sequencing (NGS)” is a catch-all term that describes a number of different modern sequencing technologies. These technologies allow for sequencing of DNA and RNA much more quickly and cheaply than sequencing methods that were used previously.  

Next-generation sequencing may be done when the cancer is first diagnosed and is also used after treatment for evaluating measurable residual disease (MRD). It can find one cancer cell among one million normal bone marrow cells. 

If PV is suspected, testing for the JAK2 gene mutation should be performed. The JAK2 V617F mutation is found in more than 95 percent of PV patients. If a patient does not have a JAK2 V617F mutation, then testing should be done for other mutations. About 2 percent to 3 percent of PV patients have the JAK2 exon 12 mutation. 

Learn more about blood tests.