Longer Procedure Duration and Large Volume Harvests Reduce the Likelihood of Achieving the Requested Cell Dose from Unrelated Bone Marrow Donors

Introduction

The factors influencing the quality of bone marrow (BM) harvests and total nucleated cell count (TNC) achieved are poorly understood. As the number of BM harvest procedures falls (due to an increasing proportion of harvest requests for peripheral blood stem cells), concerns are raised around maintaining expertise in this area. We investigate, in four Anthony Nolan collection centers, the procedure- and donor -related factors influencing the quality of harvests, and likelihood of achieving the requested TNC.

Materials & Method

110 consecutive BM harvests of healthy unrelated donors (UD)s were performed according to standard Anthony Nolan protocols. Harvest quality was defined as TNC/ml volume collected. Univariate analyses of factors influencing the TNC and harvest quality were performed using Chi squared or Fisher’s test where appropriate.

Results

110 BM harvests were performed in 80 male and 30 female donors. The median donor age was 28 years (range 18-56 years).

The median TNC requested was 4x10⁸/kg, and median harvested TNC 4.2x10⁸/kg recipient weight, with the requested TNC dose achieved in 50% of harvests. Higher volume harvests (greater than the median volume 1200 mls) were significantly less likely to achieve TNC> 4x10⁸/kg recipient weight (38% vs 70% p=0.001), as were harvests with a procedure time greater than 30 minutes (p=0.037). We investigated donor factors influencing the harvest yield and found that donor/recipient weight discrepancy significantly impacted the TNC achieved: with only 18% of BM harvests from donors who weighed less than their recipient achieving TNC >4x10⁸/kg compared to 62% harvests from donors who were heavier than their recipient (p=0.001). No other donor factor had a significant influence on the TNC.

The median TNC/ml collected was 18.2x10^6/ml and harvests in donors>40 years were more likely to be of lower quality (p=0.036). No other donor factors affected harvest quality, however a significant variation between the 4 collection centers was observed: both the harvest quality (p=0.014) and volume collected (p=0.035) varied significantly between centers.

Conclusions

Donor weight is a strong determinant of bone marrow harvest yield; we recommend that when multiple matched UDs are available, a donor with high body weight should be selected for BM harvest. Procedure factors including large volume harvests and long procedure times reduce the likelihood of achieving the requested TNC, and significant variation was seen between centers. Given the declining number of requests for BM harvests, it is crucial these are performed by the most experienced centers and that systems exist to ensure operators retain their expertise.