Work

Significance of low peripheral blood CD34+ cell numbers prior to leukapheresis: should the 5/μL threshold required for apheresis be changed?

Year: 2004

Type: article

Abstract: The pre-apheresis peripheral blood CD34+ cell count (PBCD34) is a strong predictor of the CD34+ cell collection. The final yield is also affected by the blood volume processed and the CD34+ cell collection efficiency (CE). It is common practice to apherese only when PBCD34 is 5/μL to avoid poor yields. However, many patients mobilize stem cells poorly, and the only way to get enough cells is to collect small numbers at a time over several days. Omitting apheresis because PBCD34 is below a set value may prevent them from undergoing a transplant. There are other pitfalls with this practice: it does not take the patient’s weight into account, and it ignores the possibility of improving the collection by processing more blood. Of 485 autologous harvests on Cobe Spectra over 30 months where PBCD34 was available, 104 were done with PBCD34 <5/μL. Volume processed was 15 L (n = 57) or 20 L (n = 47). A collection of ≥0.3 × 106 CD34+ cells/kg was considered acceptable as this daily yield over a week could add up to 2 × 106/kg-enough for an autograft. 60 harvests (58%) had yields of ≥0.3; with 49% being ≥0.4, 38% being ≥0.5 and 23% being ≥0.6. CE for these 104 harvests was 9–145% (median 55%) compared to 7–132% (median 45%) for the other 381 harvests performed with PBCD34 ≥5/μL (P = 0.0001). CE for the 60 harvests with CD34+ yields ≥0.3 was 30–145% (median 70) compared with 9–118% (median 35%) for the 44 with CD34+ yields <0.3 (P < 0.0001). This suggests that part of the reason for poor collection was low CE in addition to poor mobilization. The problem of low CE may be solved in part by using more experienced operators if the mononuclear cell protocol is used for apheresis or using an automated collection protocol such as AutoPBSC. These data show that an arbitrary PBCD34 threshold of 5/μL is inappropriate to deny apheresis. We suggest using the following formula for patients with PBCD34 <5/μL to decide about appropriateness of apheresis: 14n/w; where n = PBCD34/μL and w = ideal body weight in kg. A 20 L apheresis with 70% CE is assumed (20 × 0.7 = 14). If 14n/w is ≥0.3, apheresis should be performed. This approach is more logical than using an absolute threshold, and ensures that patients are not deprived of the opportunity of stem cell collection and autotransplantation. We conclude that it is clinically inappropriate to set an arbitrary minimum PBCD34 threshold for apheresis. This practice should be discontinued, and calculations individualized for each procedure.

Source: Transplantation and Cellular Therapy

DOI: 10.1016/j.bbmt.2003.12.052