Residual red cell and platelet content in WBC-reduced plasma measured by a novel flow cytometric method.
BACKGROUND
The levels of residual red blood cells (RBC) and platelets (PLT) in WBC-reduced plasma are often below the lower detection limit of automated blood cell counters. This study established a novel flow cytometric method for the enumeration of residual RBC and PLT in plasma. Furthermore, their levels in WBC-reduced plasma prepared by using various filters were investigated.


METHODS
WBC-reduced plasma was prepared from two sources: (i) filtration of buffy-coat reduced plasma using dock-on Baxter, Pall and Maco Pharma plasma filters; (ii) filtered whole blood using integral Asahi RZ2000, Maco Pharma LST1, NPBI, and Pall WBF2 whole blood filters. Residual RBC and PLT counts were assessed by using a TruCount tube (Becton Dickinson) containing a known number of lyophilized fluorescent beads. RBC and PLT were labelled with dual monoclonal antibodies, anti-CD41-R-phycoerythrin and anti-glycophorin A-fluorescein isothiocyanide, and analyzed by flow cytometer.


RESULTS
The flow cytometric method used in this method can detect residual RBC, PLT as well as RBC-MV simultaneously. The sensitivity of the assay was 50 x 10(6) cells/l with the coefficient of variations < or = 10%. Baxter and Maco Pharma plasma filters consistently reduced both RBC, RBC-MV and PLT to below 50 x 10(6/)l. Plasma derived from day 1 RZ2000 filtered whole blood contained PLT below 50 x 10(6) cells/l, whereas day 0 NPBI filtered whole blood showed the highest level of residual PLT.


CONCLUSIONS
A sensitive and accurate method for the detection of low levels RBC, RBC-MV, and PLT was established to measure their levels in WBC-reduced plasma. The procedure is simple and practical for routine quality monitoring of plasma, as well as for setting a new specification for WBC-reduced plasma.
Krailadsiri
P
P
Leucodepletion Proficiency Testing Service, National Blood Service, London, Colindale, UK.
Seghatchian
J
J
D001331:Automation; D004906:Erythrocyte Count / Q000295:instrumentation*; D005374:Filtration; D005434:Flow Cytometry / Q000379:methods*; D006801:Humans; D007937:Leukapheresis / Q000295:instrumentation; D008212:Lymphocyte Depletion; D010976:Platelet Count / Q000295:instrumentation*; D012680:Sensitivity and Specificity