- High Hb may be due to
- Increased red cell mass: True Polycythaemia
- A lack of plasma: Apparent Polycythaemia
- Primary proliferative polycythaemia (polycythaemia vera, PV)
- Hypoxic state: raised Hb serves a purpose:
- Chronic lung disease
- Cyanotic heart disease
- Inappropriately high level of erythropoietin production
- Renal cell carcinoma
- Uterine tumours
- Cerebellar haemangioblastoma
- Relative/apparent polycythaemia:
- Reduced plasma
- Dehydration, obesity, hypertension, diuretics, smoking
- Hyperviscosity symptoms
- Confusion, Altered vision, vascular insufficiency
- Repeat FBC to confirm. Check for high haematocrit.
- U&E: Check renal function.
- Uric acid: raised in some types of polycythaemia.
- Blood film: look for elevated platelets and WCC and exclude a leukaemia
- Check for JAK2 mutation (see Remember box).
- Bone marrow (see Remember box).
- Erythropoietin levels (normal or low in PV).
- Blood gases or oximetry confirm COPD or lung disease
- CXR: emphysema
- Abdominal/pelvic USS exclude uterine and renal tumours
- Bone marrow : gives additional information.
- Erythropoietin levels raised.
- Secondary polycythaemia due to lung disease: Reduce Hb by venesection (removal of 400–500 mL blood) every 2 days. Target PCV is reduced to <0.5 and in females to <0.45. Treat any underlying cause.
- Polycythaemia vera: Venesect 400–500 mL weekly. Control marrow activity with hydroxycarbamide. Use targeted therapy with JAK1 and JAK2 agonists in patients who don’t respond to first-line therapy.