Practical assessment of the suitability of IQC control materials in haemocytometry based on biologic goals

Abstract

We have assessed short and long-term imprecision goals based on biological variation in haemocytometry through internal quality control (IQC) for the following parameters: white blood cell (WBC), red blood cell (RBC) and platelet (Plt) counts, concentration of haemoglobin (Hb) and mean cell volume (MCV). The attainment of short-term imprecision goals in the IQC system with our own and commercial control blood (between-day control) presents problem for MCV, where minimum performance is achievable, the analytical coefficient of variation (CV) being less than three-quarter of the average within-subject variation (CV _I), i.e. CV<0.75 CV _I. For the other four parameters desirable performance (CV<0.50 CV _I) and even optimum performance—CV<0.25 CV _I (for WBC and Hb) is achievable. The long-term desirable imprecision goals (CV _L) based on within- and between-subject variation (CV _G) seem to be too loose. However optimum performance ${\left( {CV_{L} < 0.25{\left[ {CV^{2}_{I} + CV^{2}_{G} } \right]}^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} } \right)}$ is attainable for all five basic haemocytometry parameters. In the IQC system with retained patient specimens (within-day control), short-term imprecision goals for optimum performance are surpassed for WBC and Hb and desirable performance is achieved for RBC, MCV and Plt.