A multicenter study evaluating three methods for counting residual WBCs inWBC-reduced blood components: Nageotte hemocytometry, flow cytometry, and microfluorometry
S. Dzik et al., A multicenter study evaluating three methods for counting residual WBCs inWBC-reduced blood components: Nageotte hemocytometry, flow cytometry, and microfluorometry, TRANSFUSION, 40(5), 2000, pp. 513-520
BACKGROUND: A multicenter study was conducted to evaluate the performance c
haracteristics of flow cytometry and microfluorimetry for counting low conc
entrations of WBCs and to compare the results with Nageotte hemocytometry.
STUDY DESIGN AND METHODS: A two-phase study involving 10 centers located in
the United States and in Europe was performed. coded samples of RBCs and p
latelets were distributed by 24-hour (Phase 1) or 2-day (Phase 2) courier s
ervice to each test site for analysis. Samples were prepared to include con
centrations of WBCs slightly above and below the concentration correspondin
g to the threshold standards for WBC-reduced RBCs and platelets. All center
s tested samples by Nageotte hemocytometry plus one or both of two automate
d methods.
RESULTS: Both flow cytometry and microfluorometry gave better results than
Nageotte hemocytometry in testing freshly prepared samples. At WBC concentr
ations >5 per mu L (RBCs) or >3 per mu L (platelets), the intersite CV was
<20 percent for the automated methods but >30 percent for the Nageotte hemo
cytometer method (p<0.001). Accuracy was greater for the automated methods
than for the Nageotte hemocytometer method (p<0.001). Nageotte hemocytometr
y showed a bias to underestimation relative to the results obtained with th
e automated methods. All methods had poorer performance in testing samples
that required 12 days' shipment than in testing of those requiring overnigh
t shipment.
CONCLUSION: Automated methods for counting residual donor WBCs in WBC-reduc
ed cellular components offer advantages of improved precision and greater a
ccuracy than are seen with the Nageotte hemocytometer method. Automated met
hods are less labor-intensive but more costly than microscopic methods. Pre
paration and shipping methods will need further refinement for samples to b
e counted more than 24 hours after sample collection.