The origin and identification of unknown events associated with low‐level leucocyte counting by flow cytometry

Abstract

These previously unidentified events are probably fragmented nuclei or free DNA originating from PMN owing to a combination of ageing and reagent addition. Currently, in our protocols, the region used for WBC enumeration counts intact WBC nuclei. To achieve WBC counting consistency, flow cytometric gating protocols must be standardized, and a decision taken as to whether to include extraregional events in the count.

Comparison of a new microscopic system for the measurement of residual leucocytes in apheresis platelets with flow cytometry and manual counting

“…In contrast to Bashir et al [14], we did not observe much extra-regional events in flow cytometry in our series. Thus, we do not think that such events led to false concentrations.…”

Blood components produced from whole blood using the Atreus processing system

“…We then evaluated the in vitro quality of these components, comparing them against local, national, and European specifications for blood component quality. In addition, as it is known that longer storage times at ambient temperature provide a greater challenge to leukodepletion filters, 12,13 we used two different integral leukodepletion filters for RBC.…”

Flow cytometric determination of residual white blood cell levels in preserved samples from leukoreduced blood products

“…Several reports have indicated that an increased storage time of products before leukoreduction increases the amount of WBC fragments and cell-free DNA that ends up in the LR products 5,[21][22][23][24][25][26] and may lead to inaccurate estimates of WBC levels after leukoreduction. Although van der Meer and colleagues 26 determined that weak PI-positive events might contribute to overestimates of intact WBCs, they did not observe these in whole-blood units or buffy-coat process RBC components before 12 hours after collection with either the BD Biosciences LeucoCOUNT or LeukoSure methods on a FACSCalibur flow cytometer.…”

“…There are a number of manual and automated methods for assessing residual WBC (rWBC) counts in leukoreduced (LR) blood components. These include enumeration of white blood cells (WBCs) by flow cytometry, 1‐6 microvolume fluorometry (IMAGN 2000, BD Biosciences, Mountain View, CA), 1‐3,6 and Nageotte hemocytometer and microscopy 1,3,4,6 . Enumeration performed by flow cytometry has been performed predominantly on commercially available cytometers (FACScan or FACSCalibur, BD Biosciences; 1‐3,5 or EPICS XL, Beckman Coulter, Fullerton, CA 2‐4 ).…”

“…These include enumeration of white blood cells (WBCs) by flow cytometry, 1‐6 microvolume fluorometry (IMAGN 2000, BD Biosciences, Mountain View, CA), 1‐3,6 and Nageotte hemocytometer and microscopy 1,3,4,6 . Enumeration performed by flow cytometry has been performed predominantly on commercially available cytometers (FACScan or FACSCalibur, BD Biosciences; 1‐3,5 or EPICS XL, Beckman Coulter, Fullerton, CA 2‐4 ). Commercial kits or methods based on the same principles have been used for determination of rWBCs with commercially available flow cytometers (BD Biosciences; 1‐3,5 Beckman Coulter; 2‐4 or Cytoron, 6 Ortho Diagnostics Systems, Raritan, NJ).…”