Highly fluorescent reticulocyte count predicts haemopoietic recovery after immunosuppression for severe aplastic anaemia

Highly fluorescent reticulocyte (HFR) counts are the most reliable and sensitive index of haemopoietic recovery after bone marrow or peripheral blood stem cell transplantation. We report the behaviour of HFRs during haemopoietic recovery in two patients who were affected by severe aplastic anaemia (SAA) and treated with horse antithymocyte globulin (ATG), cyclosporin A (CsA) and granulocyte colony-stimulating factor (G-CSF). A HFR value > 5% of the total reticulocyte count, a reticulocyte count > 30 x 10(9)/l, and a polymorphonuclear (PMN) count > 0.5 x 10(9)/l were found after 9 and 8, 20 and 46, and 16 and 22 days, respectively, after the end of ATG. HFR recovery to > 5% anticipated the rise of PMN > 0.5 x 10(9)/l by at least 7 and 14 days, respectively. Thus, HFR evaluation could be used as a reliable and early marker of response to immunosuppression in severe aplastic anaemia.