USE OF PRECISION PROFILES TO EVALUATE PRECISION OF THE AUTOMATED LEUKOCYTE DIFFERENTIAL

The commonly used methods of assessing the precision of the automated leukocyte differential have certain drawbacks that affect the validity and comparability of results. In the present report, we introduce a p rocedure based on building precision profiles from a large number of w ithin-run imprecision experiments. The profiles are fitted to the func tion for the CV of proportions, which yields the number of theoretical ly differentiated leukocytes. Differences between fitted curves are ev aluated for statistical significance by the F-test. As an example, we compared the precision of two hematology analyzers, a flow-cytometric technique involving fluorescence-labeled monoclonal antibodies, and th e manual differential. We were able to establish definite differences in precision between different analyzers and different leukocyte class es. Our data also indicated that conventional within-run imprecision s tudies may completely misjudge analyzer precision. Furthermore, we cou ld demonstrate that the precision of analyzers that analyze a fixed am ount of blood rather than a fixed number of leukocytes is strongly inf luenced by the leukocyte count of the sample, leading to high imprecis ion for leukopenic samples. We believe the proposed procedure is a use ful addition to currently used protocols; it yields clear results and creates a statistical basis of comparison between various instruments and techniques of differentiation.