Presence of Promyelocytes in Peripheral Blood as a Novel Predictor of Optimal Timing for Single-Step Peripheral Blood Stem Cell Collection

Background: Because peripheral blood stem cell (PBSC) collection places a burden on the patient and should ideally be completed in a single procedure, a convenient clinical predictive factor is needed. Methods: This retrospective study included 72 patients who underwent autologous PBSC collection. A median volume of 3.9 × 106 CD34-positive cells/kg (range: 0.3-47.4 × 106 cells/kg) was collected on the first day. We defined failure as inability to collect 2.0 × 106 cells/kg on the first day. PBSC collection was classified as failed (n = 25, 34.7%) and successful (n = 47, 65.3%), and patient clinical characteristics were analyzed. Results: The success group had significantly more cases in which a differential white blood cell count in peripheral blood on the day of PBSC collection detected promyelocytes (n = 34 [72.3%] vs. n = 11 [44.0%] in the failure group; P = 0.008). Sixty-two patients underwent autologous PBSC transplantation (median number of transplanted cells, 5.6 × 106/μL; range: 1.60-47.4 × 106 cells/μL). Among transplanted patients, the success and failure groups did not significantly differ in relation to the interval until neutrophil, platelet, or red blood cell engraftment. Conclusion: The presence of promyelocytes in peripheral blood may be a useful indicator of the optimal timing for single-step PBSC collection.