Comparative Study for Measurement of Residual Leucocytes in Leucodepleted Red Blood Cells by Two Different Methods.

Estimation of residual leukocytes in blood components after leukodepletion is crucial for assessment of quality. Flow cytometry (FC) and Nageotte hemocytometer are the most widely accepted methods for counting residual white blood cells (rWBCs) in leucocyte-depleted (LD) blood components. The objective of this study was to compare use of Nageotte counting chamber and FC for quality control of leukodepleted red cell units. A prospective, observational study was conducted in the department of Transfusion Medicine. A total of 80 whole blood donations from healthy donors were subjected to testing by FC and Nageotte hemocytometer for estimation of rWBC in duplicate. Additionally, ten personnel attempted a survey for ease of use of FC. Number of rWBC detected by flow cytometer were between 1 WBC/μL and 28 WBCs/μL whereas that detected by Nageotte's chamber were between 0 WBC/μL (lowest) and 5 WBCs/μL. Coefficient of variation was found to be 87.36% by Nageotte hemocytometer method and 43.26% by FC. Linear regression analysis did not show any correlation (R-squared = 0.01,  = 0.13) between the two methods which signifies that the two methods cannot be used interchangeably. Pearson's correlation coefficient showed a weak relation between results obtained by the two methods. Inter-observer variation was found to be significant with use of Nageotte hemocytometry. Survey for ease of use of FC indicated acceptability of FC with favorable scores. Flow cytometric technique provides a reproducible and objective tool for counting rWBC in leukodepleted blood components compared with the Nageotte hemocytometer.