Comparison of Flow Cytometric Methods for the Enumeration of Residual Leucocytes in Leucoreduced Blood Products: A Multicenter Study

Comparative study of quality of leukoreduced packed red blood cell units as assessed by nageotte hemocytometry and flow cytometry

PURPOSE

Assessment of residual white blood cell (rWBC) count is vital to ascertain the quality of leukodepleted (LD) blood components. Automated cell analyzers lack the sensitivity for the assessment of very few leukocytes as found in LD blood components. Flow Cytometry (FC) based methods and Nageotte hemocytometer are the most commonly used techniques for this purpose. The objective of this study was to compare the use of Nageotte hemocytometer and FC for quality control of LD red blood cell units.

MATERIALS AND METHODS

A prospective, observational study was conducted in the Department of Immunohematology and Blood Transfusion of a tertiary care center from September 2018 to September 2020. About 303 LD-packed red blood cell units were tested by FC and Nageotte hemocytometer for rWBCs.

RESULTS

The number of rWBC (mean) detected by flow cytometer and Nageotte's hemocytometer was 1.06 ± 0.43 white blood cell (WBC)/μL and 0.67 ± 0.39 WBC/μL, respectively. Coefficient of variation was 58.37% by Nageotte hemocytometer method and 40.46% by FC. Linear regression analysis did not show any correlation (R2= 0.098, P = 0.001) whereas Pearson's correlation coefficient showed a weak relation (r = 0.31) between the two methods.

CONCLUSION

Flow cytometric technique provides a more precise and accurate objective tool compared to Nageotte hemocytometer which is labor intensive, time consuming, and prone to errors arising out of subjectivity along with reported underestimation bias. In the absence of adequate infrastructure, resources, and trained workforce, Nageotte hemocytometer method is a reliable alternative. Nageotte's chamber could be best used in the resource-constrained setup as it offers a relatively inexpensive, simple, and viable means to enumerate rWBCs.

An evaluation of a volumetric method for the flow cytometric determination of residual leukocytes in blood transfusion units

The removal of leukocytes from blood components helps to prevent or reduce some adverse reactions that occur after blood transfusions. The implementation of the leukodepletion process in the preparation of blood units requires quality control, consisting of a reliable cell counting method to determine residual leukocytes in blood components. The most widely used methodology is a flow cytometric bead-based counting method. To avoid the need for commercial counting beads, we evaluated a volumetric counting method of leukocyte enumeration. A total of 160 specimens of leukodepleted plasma, red cell and platelet units, as well as 58 samples of commercially available controls containing different concentration levels of leukocytes, were included in the study. The conventional quality control method using the bead-based counting method performed with the FACSCalibur flow cytometer was compared to the bead-based counting method and the volumetric counting method performed with the MACSQuant 10 flow cytometer. Our results show that the MACSQuant bead-based method, as well as the volumetric MACSQuant method, meet the sensitivity requirements of residual leukocyte enumeration when compared to the gold standard, bead-based FACSCalibur method. We conclude that the volumetric method can be a substitute for the bead-based counting of residual leukocytes in a variety of blood components.

Standardization of a compensation matrix for the use in an ISHAGE-based single-platform for CD34+ stem cell quantitation on the FACSVia™ flow cytometer

INTRODUCTION

Becton Dickinson (BD) FACSVia™ is a recently developed flow cytometer with which worldwide clinical experience is limited. Recently, our center started using the single-platform BD Stem Cell Kit (BD SCE) for the quantitation of viable CD34+ (7-aminoactinomycin D-7-AAD-negative cells) on a BD FACSVia™. Currently, there are no formal recommendations for the fluorescence compensation of 7-AAD in this scenario.

METHODS

A 3-color fluorescence compensation matrix ("Optimized BD CS&T") was standardized based on the fluorescence of 7-AAD in samples of 27 individuals. The "Optimized BD CS&T" was compared with manual compensation (predicated method) and BD CS&T beads.

RESULTS

The analysis of the viable CD34+ cells/mm³ showed a very strong correlation between the manual compensation versus "Optimized BD CS&T" (r = 1.00) and manual versus BD CS&T (r = .99). The analysis of CD34+ viability (%) showed a very strong correlation for manual versus "Optimized BD CS&T" (r = .99). However, for manual versus BD CS&T, the correlation was inferior (r = .86). For viable CD34+ cells/mm³ , Bland-Altman plots showed a better concordance between manual and "Optimized BD CS&T" than between manual and BD CS&T. For CD34+ viability (%), the concordance was very good between manual and "Optimized BD CS&T", while there was a poor concordance between manual and BD CS&T.

CONCLUSION

"Optimized BD CS&T" matrix proved to be more precise than the conventional BD CS&T beads. The "Optimized BD CS&T" matrix can be used along with BD SCE kit on BD FACSVia™ flow cytometers.

The use of a hematology analyzer with a new generation of software as an alternative to flow cytometry for enumerating residual white blood cells in blood components

BACKGROUND

Leukoreduction of blood components was implemented to reduce transfusion‐associated risks. The detection level for residual white blood cells (rWBCs) required to demonstrate leukoreduction was originally considered too low for hematology analyzers. Developments enabling cell counts in body fluids have, however, renewed interest in rWBC counting. An assessment of Sysmex XN hematology analyzers with software offering automated rWBC enumeration intended for use on blood components was performed.

STUDY DESIGN AND METHODS

Performance characteristics were determined using platelet, red blood cell (RBC), and plasma samples spiked with WBCs. Subsequently, components (platelets, n = 1367; and plasma, n = 80) were tested and results compared with flow cytometry, to monitor leukoreduction efficiency to a level of less than 1 × 10⁶/unit. Components identified by flow cytometry as having poor leukoreduction, exceeding this limit, were also tested (platelets, n = 3; and RBCs, n = 10).

RESULTS

Linearity studies up to 32 WBCs/μL showed good correlation between observed and expected results (R² > 0.9996). Precision analysis gave an average limit of quantitation of 2 WBCs/μL with coefficients of variation less than 20%. Average carryover was 0.1%. Plain sample tubes were a source of aberrant results with routine components. Using ethylenediaminetetraacetic acid tubes the analyzer gave results greater than 1 × 10⁶/unit in 2.7% of cases compared with 1.4% by flow cytometry, but overall results were within specification, with more than 90% of components having rWBC values below the limit. All incidences of poor leukoreduction, with flow cytometry results greater than 13 rWBCs/μL were correctly identified, with an excellent correlation between results (R² = 0.9818).

CONCLUSION

The analyzer demonstrated acceptable performance characteristics for enumeration of rWBCs; consequently, additional multisite evaluations are warranted.

http://onlinelibrary.wiley.com/doi/10.1111/trf.15642/full