Counting low numbers of leukocytes in leukoreduced blood components

Numerous assays have been developed to measure the residual concentration o f leukocytes in leukoreduced blood components. The performance characterist ics of these assays are critical for process control of leukoreduction, eva luation of new devices, and clinical investigation. Not all assays, ape equ ally robust, however, and users should evaluate assays based. on standard p rinciples of performance. Five major performance characteristics of countin g assays include: accuracy and bias, Linearity, limit of detection, precisi on or reproducibility, and portability In particular, the lower limit of de tection has been used with various meanings in the literature. Laboratories considering using a particular counting assay can use the enclosed guideli nes to evaluate the performance of the technique. In the future, the use of automated counting methods for counting very low levels of residual donor leukocytes is likely to become more widespread.