Canterbury DHB

Primary polycythaemia - joint management between specialist care and primary care

Primary polycythaemia

About 100 people in Christchurch have primary polycythaemia, which is a myeloproliferative disorder found typically in middle aged adults. It may be diagnosed incidentally in a person with a sustained elevated haemoglobin (or haematocrit), not secondary to any other cause such as hypoxia from lung disease. The principal problem seen is a greatly increased incidence of venous and arterial thromboses. Patients may continue with this chronic disorder for many years, and remain well. Occasional patients may progress to develop other related haematological disorders such as acute leukaemia or myelofibrosis.

Risk Assessment and Requirement for Treatment

All patients with primary polycythaemia are at increased risk of thrombosis. There is an evidence-based case that this risk is dramatically reduced by maintaining the haematocrit below 0.45 in men and 0.42 in women. In addition patients benefit from low dose aspirin which should be given if there are no contraindications. The haematocrit may be kept low by periodic venesection or hydroxyurea.

Venesection Therapy

This is performed in haematology outpatients. 400 ml of blood is removed over 20 minutes. If the patient would be considered fit enough to be a blood donor, no saline replacement is given. The procedure is repeated as often as necessary, typically two monthly. The patient often becomes iron deficient. This should not be replaced, otherwise polycythaemia is exacerbated.

Hydroxyurea Treatment

Hydroxyurea is presented in capsules containing 500 mg. Patients typically take between 500 mg - 1500 mg daily in a single dose in the morning. The drug is usually well tolerated and patients do not typically have side effects of nausea or alopecia. Macrocytosis is usual. The principal side effect is excessive myelosuppression, so the blood count should be monitored at intervals to check it remains near normal, and in particular that haematocrit is < 0.45 (men) or < 0.42 (women). A typical monitoring interval in a stable patient is two monthly. Hydroxyurea dose often remains stable over many years and often only small changes are necessary, for example from one 500 mg tablet daily to one daily but two on Monday and Thursday. Occasional patients can get atypical skin reactions, particularly painful ulcers in the lower parts of the leg. Such patients cannot continue with hydroxyurea and require a second line treatment.

Joint Treatment Plan

This is suitable for patients who are well and are either on no treatment or who have been stabilised on hydroxyurea. It resembles a treatment plan for patients with other chronic disorders such as hypertension or diabetes and to the monitoring of treatments such as anticoagulation. The principal difference is that each general practitioner may only have one or two patients with primary polycythaemia. The aim of treatment is to maintain the patient in good health, reducing the risk of thrombosis by myelosuppression using hydroxyurea if appropriate. Patients will be reviewed as necessary and at least yearly by a haematologist. At other times they will remain under the care of their primary care physician. If the patient is on treatment with hydroxyurea, this will be monitored and prescribed by their primary care physician. If the patient is well, appropriate monitoring would usually be by the patient having a blood test and the result of the blood test then being compared to previous results, with advice being given (perhaps by phone) about whether there is any need for a change in dose. The patient’s haematologist would usually be consulted if anything unexpected occurred or there were any uncertainty.

Topic Code: 31422