Evaluation of total leukocytes count by flow cytometry with Beckman Coulter® DXH900 in the presence of platelet aggregates.

The Beckman Coulter® DXH900 uses the impedance method to measure the total leukocytes count. In presence of platelet aggregates, the device identifies the structural changes and associates an alarm with the leukocytes result. The aim of this study was to evaluate the influence of platelet aggregates using the principle of flow cytometry as a second assessment of the white blood cell count. Total leukocytes count was evaluated in 49 specimens with presence of platelet aggregates and 32 without anomaly. The differences between total leukocyte count by the two automatic methods (impedance and flow cytometry) and the microscopic method were compared. Without platelet aggregates, the median values were 5.6 (microscopic cell count), 5.4 (impedance) and 5.4 (flow cytometry) and no discordance was observed. In presence of platelet aggregates, the median values were 5.6, 6.4 and 5.1 respectively. The graphical analysis with the allowable total error range of ± 25.7% showed substantial analytical discrepancies (15/49) using impedance method while the flow cytometry method revealed minor disagreements (3/49). Analytical discordances versus WBC reference ranges showed 88% agreement and a substantial Kappa coefficient of 0.70 by impedance, while the flow cytometry method had 94% agreement and a perfect Kappa coefficient of 0.83. The formation of platelet aggregates increased the total leukocyte count performed DXH900 impedance method. Our study has shown that DXH 900 flow cytometry method may be an alternative to exclude the presence of pseudoleukocytosis. In case flags are generated, the microscopic method may be needed for the confirmation of WBC count.

Impact of preanalytical storage on the measurement of erythrocyte sedimentation rate using an infrared microphotometer system (TEST1).

This study examined the influence of temperature and time on the pre-analytical stability of the erythrocyte sedimentation rate (ESR) measured on a TEST1 system. The first experiment included 102 samples stored at room temperature and the second experiment included 112 subjects and investigated refrigerated (2-8 °C) storage. Our study showed a stable ESR results at room temperature (15-25 °C) up to 8 h (p = 0.512). Samples stored at 2-8 °C for 24 h were stable (p = 0.280) for 24 h.