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Polycythaemia (DRAFT)

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Elevated haemoglobin / haematocrit has a wide differential diagnosis:

  • Secondary causes (such as hypoxic lung disease, cyanotic heart disease, smoking, obstructive sleep apnoea and erythropoietin-secreting tumours). Venesection not usually indicated.
  • Relative polycythaemia resulting from plasma depletion (e.g. diuretics, alcohol); lifestyle modification required.
  • Polycythaemia vera (primary polycythaemia).

The threshold for therapeutic intervention with venesection or cytoreductive therapy in an individual patient depends on the cause, associated symptoms and thrombotic risk factors. For most secondary or relative causes of polycythaemia there is no evidence to support intervention with venesection. Co-existing iron deficiency can sometimes mask the presence of polycythaemia vera.

Who to refer

Refer for outpatient assessment:

  • Confirmed extreme raised haematocrit (Male >0.600, Female >0.560) in the absence of congenital cyanotic heart disease or hypoxic lung disease.
  • Persistently raised haematocrit (Male >0.510, Female >0.480) in association with recent arterial or venous thrombosis (including DVT / PE, CVA / TIA, MI / unstable angina, PVD) or neurological symptoms such as loss of vision (urgent assessment required).

Referral for specialist opinion should be considered for:

  • Elevated haematocrit (Male >0.510, Female >0.480) in association with: past history of arterial or venous thrombosis, splenomegaly, pruritus, elevated white cell or platelet counts.
  • Persistent unexplained elevated haematocrit (Male >0.510, Female >0.480)

Discharge policy

  • Following completion of investigation, only those cases requiring venesection or cytoreductive therapy will remain under outpatient follow-up.
  • All other cases will be discharged with a suggested frequency of FBC monitoring and a clearly-stated threshold haematocrit for re-referral.

Red flags

Raised haematocrit with:

  • Recent arterial or venous thrombosis (incl. DVT/PE, CVA/TIA, MI/unstable angina, PVD)
  • Neurological symptoms (e.g. loss of vision)

Before referral

Assessment and Investigations in primary care prior to referral


  • More than one similar result? Assessed on sample taken with no / minimal tourniquet time.
  • Any history of chronic lung disease, obstructive sleep apnoea, congenital cardiac disease?
  • Any history of arterial or venous thrombosis?
  • Other arterial risk factors? Hypertension?
  • Smoking, alcohol and medications (especially diuretics)
  • Any generalised pruruitus or splenomegaly?

Investigations in primary care:

  • SaO2, blood pressure and urine dipstick
  • Repeat FBC uncuffed, renal and liver function, glucose
  • Consider CXR or other respiratory investigations according to symptoms


Investigation in primary care for patients not meeting criteria for referral:

  • Confirm with repeat FBCs over time (ensure no/minimal tourniquet venostasis for blood samples)
  • Modify known associated lifestyle factors: smoking, alcohol, use non-diuretic anti-hypertensive agents.
  • Screen for diabetes mellitus.


URGENT ADVICE: 9am to 5pm via hospital switchboard for haematology SpR. ONLY for emergency advice. Out of hours and weekends – emergency advice may be obtained from the on-call haematology clinician via hospital switchboard.

NON-URGENT ADVICE: use Haematology advice and guidance service which can be accessed through the NHS e-referral system. Your query will be responded by a consultant haematologist within 3 working days.

REFERRAL: via e-RS or cancer fast track pathways as indicated.

Minimal information: the referral letter should include abnormal clinical findings (location, size, any associated features) and any abnormal full blood count results or other relevant test results, particularly if these investigations were not done in laboratories of the hospital to which the referral is made.

Cancer fast track: ensure that the location and size of any lymphadenopathy is described. According to NICE guidance and previous section in this guidance.

Other haematology referrals: most new referrals should go to one of the general haematology clinics but may be triaged to a specialist clinic.


BSH guidelines:

Efforts are made to ensure the accuracy and agreement of these guidelines, including any content uploaded, referred to or linked to from the system. However, BNSSG ICB cannot guarantee this. This guidance does not override the individual responsibility of healthcare professionals to make decisions appropriate to the circumstances of the individual patient, in consultation with the patient and/or guardian or carer, in accordance with the mental capacity act, and informed by the summary of product characteristics of any drugs they are considering. Practitioners are required to perform their duties in accordance with the law and their regulators and nothing in this guidance should be interpreted in a way that would be inconsistent with compliance with those duties.

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