QUANTITATIVE RETICULOCYTE ANALYSIS MAY BE OF BENEFIT IN MONITORING ERYTHROPOIETIN TREATMENT IN DIALYSIS PATIENTS

Reticulocyte responses to low-dose erythropoietin (EPO) were monitored using automated flow cytometric analysis. Sixteen adult dialysis pati ents were treated with 1,000 U of recombinant human EPO (rHuEPO), subc utaneously, thrice weekly (mean dose 15.7, SD 3.7 U/kg). The reticuloc yte count (baseline 31.1, SD 19.1 x 10(9)/L) increased in 14 patients in the first week, with a peak response occurring at Week 2 (mean 57.3 , SD 26.5 x 10(9)/L, p < 0.01), There was a wide spectrum of response, the maximal absolute increment ranging from 6.8-69.7 x 10(9)/L (maxim al percentage increase 19-863%). Overall there was no relationship bet ween the early increment in reticulocyte count and hemoglobin (Hb) res ponse over the ensuing 4 months. Nine patients became transfusion inde pendent (mean Hb increasing from 6.9, SD 0.8-9.2, SD 1.2 g/dl). Two pa tients had poor reticulocyte increments and no significant change in H b. The remaining 5 patients responded partially with a brisk reticuloc yte response and a marked reduction in transfusion dependency, but wit hout a sustained increase in Hb. On investigation, all had gastrointes tinal bleeding (melena in 1, commencing after initiation of treatment, positive fecal occult bloods in 4), whereas none of the other patient s showed evidence of blood loss. It is notable that the erythron was s ensitive to this modest dose of rHuEPO in the majority of patients as evidenced by the reticulocyte response. The results provide useful inf ormation in the management of patients on rHuEPO. A small or inapparen t reticulocyte response suggests a confounding factor; a poor Hb respo nse in the presence of active reticulocyte synthesis points to occult blood loss or hemolysis.