How PV is diagnosed and treated

Some people with PV have few, if any symptoms. Sometimes PV is only picked up after a routine blood test shows that a person has a high red blood cell count.

About 30% of PV cases are diagnosed following a heart attack or a stroke.

The goal of treatment is to manage symptoms and reduce the risk of complications such as blood clots. The type of treatment will depend on factors such as the likelihood of developing complications, a person’s age and general health.

Patients at high risk of heart disease will be given advice on ways of managing other health problems such as diabetes, high cholesterol and high blood pressure.

The treatment landscape of PV is constantly evolving. New treatment approaches currently under investigation have the potential to further improve the outlook for people with PV.

+ How is PV diagnosed?

• PV is usually diagnosed following a full blood count (a blood test, which counts the number of red and white blood cells and platelets)
• If PV is suspected a further blood test may be used to check for the JAK2 gene variation (mutation)
• Other blood tests may also be used to check levels of iron, vitamin B12, erythropoietin (EPO), a hormone involved in red blood cell production, and oxygen
• An ultrasound scan of the abdominal (tummy) area may be performed to check the spleen
• A chest x-ray may be carried out to examine the lungs and the heart
• If PV (or another blood disorder) is suspected, a bone marrow test will be carried out to examine the contents of the bone marrow. This involves removing a small sample of liquid bone marrow, usually from the hip or pelvis, under local anaesthetic. This is known as bone marrow aspiration. The sample is examined under a microscope to check for abnormalities.

How is PV treated?

Treatments for PV are intended to lower the production of blood cells and help to maintain a normal blood volume (this is known as cytoreductive therapy). The aim is to manage symptoms and reduce the risk of complications. The combination of treatments used will be tailored to each person based on age, symptoms, blood count and general health. Everyone with PV should have regular check-ups with their healthcare team and blood tests, including hematocrit levels (the proportion of red blood cells in the blood).

Doctors assess a number of factors to work out whether a person living with PV is at low, intermediate or high risk of developing a blood clot (thrombosis). The following factors can increase the risk of a blood clot:

• The person in question has previously suffered a blood clot
• Smoking
• High blood pressure
• Diabetes

People with PV at low risk of complications may only require low-dose aspirin therapy and venesection/ phlebotomy (also known as bloodletting, which is regular removal of blood) to manage the condition.

Those at greater risk of complications may be treated with one or more drugs that aim to slow production of blood cells and reduce blood ‘stickiness’ to help maintain a normal blood flow. If a person is dealing with conditions such as diabetes, high blood pressure and high cholesterol, they will be given advice on ways of managing these conditions.

+ Key treatment options

• Venesection/phlebotomy/bloodletting: an intravenous (IV) needle is inserted in a vein to remove blood in the same way as when blood is donated. This is repeated on a regular basis to reduce the number of red blood cells and make the blood thinner
• Antiplatelet drugs: e.g. low-dose aspirin, dipyridamole or clopidogrel are used to thin the blood and help prevent blood clots
• Anticoagulants: medicines that help to prevent blood clots, such as warfarin or heparin. These may be given in tablet or injection form
• Hydroxycarbamide (or hydroxyurea): a type of chemotherapy drug in capsule form designed to interfere with the growth of cancer cells – in this case, helping to lower the number of red blood cells and platelets
• Busulfan: a type of chemotherapy in tablet form that targets the bone marrow and helps to reduce the blood count
• Interferon alpha: a substance which occurs naturally in the body that reduces the production of bone marrow cells. Interferon is given by injection
• JAK inhibitors: Ruxolitinib is a type of targeted therapy drug known as a protein kinase inhibitor. It is designed to block the function of JAK1 and JAK2, slowing down blood production and reducing the size of the spleen. Ruxolitinib may be given to patients who cannot take hydroxycarbamide or who no longer respond to it
• Anagrelide: a platelet-reducing agent in capsule form may be used in some countries, particularly in patients who do not respond to hydroxycarbamide
• Allopurinol: a treatment used to prevent and treat gout
• Antihistamines: may be prescribed to relieve itching
• Phototherapy (UV light therapy): may be used to treat itching

+ Which healthcare professionals oversee the care of people with PV?

• PV is usually diagnosed and treated by a hematologist (a specialist in blood disorders) and their team. A hematologist will prescribe treatment and monitor for any potential side effects of therapy.
• People with mild forms of PV may require little treatment other than regular check-ups and blood tests. Some of these may be carried out by a family doctor or general practitioner (GP).
• Patients who experience heart problems may need to see a cardiologist (specialist in heart disease).

+ Are there any new treatments on the horizon?

• New treatment options are currently being investigated in clinical trials throughout the world. These include combinations of new and existing therapies and targeted therapies
• A number of other novel therapies are also being investigated. Silence Therapeutics is investigating gene ‘silencing’ therapies, which are designed to temporarily block a specific gene’s message that would otherwise trigger an unwanted effect

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