Clinical guidelines Investigation of patients with polycythaemia

Polycythaemia may complicate or be the presenting feature ofa wide variety of different pathologies. Early diagnosis and treatment of primary polycythaemia will significantly reduce the morbidity and mortality associated with this condition. Patients with a raised packed cell volume are divided into those with a raised red cell mass (absolute polycythaemia), and those with a red cell mass within their normal range (apparent polycythaemia). A standard investigative approach ofan absolute polycythaemia enables patients with primary and secondary polycythaemia to be identified, leaving a group termed idiopathic erythrocytosis. There are a number of physiological situations and pathological events associated with idiopathic erythrocytosis and apparent polycythaemia. Careful follow-up of both groups of these patients is essential to identify possible causative mechanisms.