A hematology analyzer can be suitable to count residual cells in blood components

Flow cytometry is currently used in many laboratories to measure residual cells in blood components, which needs to be performed as part of routine quality control measurements. However, since recently the so-called blood bank mode software is available for the Sysmex XN-1000 and XN-2000 hematology analyzers, providing an alternative method. There is still uncertainty if results of the hematology analyzer are comparable to flow cytometry when counting residual cells in blood components.

In the present study, residual cells were measured in red blood cell concentrates (RCCs), plasma and platelet concentrates (PCs) using two different measuring approaches: flow cytometry (BD FACS Lyric) and the blood bank mode software of a hematology analyzer (Sysmex XN-1000). Medians of residual cells per µL were quantified using Bland-Altman analysis and Spearman correlation for all measured residual cell types including residual white blood cells (rWBC) in RCCs, plasma and PCs, residual red blood cells (rRBC) in plasma and PCs and residual platelets (rPLT) in plasma. Furthermore, we quantified pass rates according to cut-off value guidelines.

No significant differences were detected in RCCs that were manufactured in a system using whole blood in-line filtration, as a median of 0.4 (interquartile range (IQR): 0.2-0.7) rWBC/µL was detected by FACS compared to 0.4 (0.2-0.9) rWBC/µL when using XN-1000 (n=61). In red cell in-line filtrated RCCs a median of 0.1 (0.0.-0.2) rWBC/µL was detected by FACS compared to 0.1 (0.1-0.3) rWBC/µL by XN-1000 (n=40) which was also not significantly different. In plasma, rWBC/µL were also highly similar when using FACS compared to XN-1000 (n=60). In contrast, in pooled PCs (after pathogen inactivation (PI) with Intercept), significantly higher rWBCs/µL were detected (1.1 (0.4-1.7) rWBC/µL when using FACS and 2.3 (1.4-3.0) rWBC/µL when using XN-1000) (n=34).

The blood bank mode software of the Sysmex XN-1000 hematology analyzer is a useful and reliable tool to count residual cells (rWBC, rRBC, rPLT) in blood components (RCCs and plasma) instead of using flow cytometry. This is highly valuable as costs and handling times by staff are reduced by using this new methodological approach. However, especially when concerning pooled PCs after PI, rWBCs are significantly higher when using the XN-1000 and therefore flow cytometry might still be required.

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