Circulating burst-forming unit-erythroid (BFU-E) colonies as an early marker to measure the recombinant human erythropoietin response in peritoneal dialysis patients.

To evaluate circulating burst-forming unit-erythroid (BFU-E) cells after erythropoietin (EPO) treatment, 7 female continuous ambulatory peritoneal dialysis patients were studied [baseline hemoglobin (HB): 7-10.5 g/dL)]. EPO (4000 U subcutaneously) was administered twice weekly for two months. The control group consisted of 7 healthy women with similar demographic characteristics. Mononuclear cells (MC) (5 x 10(5)) were added to 1 mL of culture medium, supplemented with 30% fetal bovine serum, 2 U/mL of EPO, 1% bovine serum albumin, and 0.3% agar. To enumerate colonies derived from each circulating BFU-E, plates were examined by inverse light microscopy, identifying BFU-E as large aggregates with more than 100 hemoglobinized cells (HC). A remarkable individual response was observed, with Hb values ranging 8.4-13.6 g/dL at week 4 and 8.8-16.5 g/dL at week 8. Baseline levels of BFU-E in patients ranged 0-100/5 x 10(5) MC (0-358 mL of whole blood), and in controls they ranged 6-24/5 x 10(5) MC (29.6-101.3/mL) (NS). Hemoglobin levels after four and eight weeks of EPO showed a significant relationship with circulating BFU-E at baseline (r = -0.873, r = -0.928, respectively). The increment in Hb after eight weeks showed a significant relationship with baseline BFU-E (r = 0.812). Hemoglobin levels at the fourth to eighth week, and the increment in Hb after eight weeks, showed a significant, direct relationship with the increments in circulating BFU-E registered after one to two weeks of treatment. We conclude that, after the first week of EPO treatment, its effect on hemoglobin may be predieted by the increment in circulating BFU-E. Thus; a new tool to measure the earliest EPO effects has become available.