A multicenter study evaluating three methods for counting residual WBCs inWBC-reduced blood components: Nageotte hemocytometry, flow cytometry, and microfluorometry

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.