[Reticulocytes in the diagnosis of anaemia].

Reticulocytes are immature erythrocytes; the number of reticulocytes in the peripheral blood reflects erythropoietic activity. Two cases are described to illustrate the use of the reticulocyte count in the diagnostic workup of anaemia. The first patient was a 62-year-old woman presenting with fatigue. Laboratory evaluation showed severe macrocytic anaemia, thrombocytopaenia and the presence of schistocytes. A low reticulocyte count suggested decreased erythropoiesis underlying the anaemia; this led to the diagnosis of vitamin B12 deficiency. The second patient, a 52-year-old woman, also presented with fatigue and macrocytic anaemia. A high reticulocyte count indicated increased erythrocyte degradation, and the patient was eventually diagnosed with autoimmune haemolytic anaemia. The role of reticulocytes in the differential diagnostic workup of anaemia was explored on the basis of these case descriptions. The test methodology, analytical performance, reference values and pitfalls were discussed, as well as the reticulocyte indices and their use in monitoring therapy.