Morphology in the diagnosis of red cell disorders.

Despite the advances in automated blood cell counting, the blood film retains a crucial role in the diagnosis of red cell disorders. It is particularly important in haemolytic anaemias and in the differential diagnosis of macrocytic anaemia. However, all cases of anaemia in which the diagnosis is not immediately obvious require a blood film. Blood film examination sometimes provides a definitive diagnosis but more often suggests a differential diagnosis that indicates which further tests are most appropriate. The blood film has the advantage of speed; this is clinically important in any severe anaemia but particularly in acute haemolytic anaemia, thrombotic thrombocytopenic purpura and megaloblastic anaemia. Polycythaemic as well as anaemic patients require blood film examination.