Counting of residual WBCs in WBC-reduced blood components: a multicenter evaluation of a microvolume fluorimeter by the United Kingdom National BloodService

BACKGROUND: Implementation of universal WBC reduction of blood components m eans that automated analytical methods may be the only satisfactory way for production laboratories to meet increased testing requirements. STUDY DESIGN AND METHODS: A multicenter study on the performance of a micro volume fluorimeter (IMAGN 2000, Becton Dickinson) was undertaken on 519 RBC , 353 platelet, and 27 fresh plasma units. RESULTS: WBC counts for the RBC samples ranged from 0.02 to 6.94 x 10(6) pe r unit (mean, 0.57) as determined by FC and from 0.02 to 5.53 x 10(6) per u nit (mean, 0.40) as determined by MVF with a mean FC bias of +0.15 x 10(6) WBCs per unit, and discrepancies outside the 95% limits of agreement were m ainly associated with higher FC counts. The series of platelet samples show ed means of 0.90 (range, 0.06-19.45) and 0.66 (range, 0.01-18.95) x 10(6) W BCs per unit for FC and MVF methods, respectively. FC and MVF results were in good agreement at low counts, although significant discrepancies were no ted at higher counts. Overall, for the platelet units, there was a mean FC bias of +0.34 x 10(6) WBCs per unit. The intermethod agreement exceeded 99 percent for both types of blood component when the single (both UK and Unit ed States) decision point of 5.0 x 10(6) WBCs per unit was applied. The mea n WBC counts for the 27 analyzed fresh plasma units were 61.8, 56.0, and 46 .0 per muL by Nageotte hemocytometry, FC, and MVF, respectively. CONCLUSIONS: This evaluation found that the level of intersite consistency for FC was relatively poor compared to that for MVF. The results neverthele ss validated the broad equivalence of FC and MVF results for the current Co uncil of Europe and UK/US decision points of <1.0 and <5.0 x 10(6) WBCs per unit.