Apheresis machines variably overestimate mononuclear cell collection volume

Calculation of the actual number of CD34+ cells in the collection product is based on the volume of the collected product and its concentration of CD34+ cells measured in the lab. The number of CD34+ cells infused correlates closely with the pace of hematopoietic reconstitution following autologous or allogeneic stem cell transplantation.

We studied peripheral blood stem cell collections in a single apheresis center with two Spectra Optia devices, using mononuclear cell collection or continuous mononuclear cell collection procedures. The collection volume displayed by the apheresis device was compared with the volume determined by a weight-based method.

Fifty-two consecutive CD34 collections in 35 different donors (range 1-4 daily procedures per donor) were analyzed. The machines reported larger collection volumes (P < .001). The mean collection volume reported by the machine was 274.37 mL (range 162-396). The mean manually measured collection volume was 261.82 mL (range 155-371.40). Mean overestimation by machine was 12.53 mL (range -0.95 to 31.24; 95% confidence interval 10.94-14.11) or 4.88% (range -0.26 to 10.28). Median overestimation of the absolute number of CD34 was 10.29 × 10⁶ (range -2.83 to 141.84 × 10⁶ ).

Both Spectra Optia machines overestimated the collection volume after peripheral blood stem cell collection. Although the mean variation falls within the expected range, in some cases, this overestimation may be clinically relevant if no other method of measurement is used.