Analytical Features of the New Red Blood Cell and White Blood Cell LH750 Research Population Data.

Recently, a new set of parameters produced by the Beckman-Coulter’s GEN’S, LH500, LH750 and the latest LH780 automated blood counters, derived from leukocyte and red cell’s morphological data by means of the VCS technology are available and can be printed as research data together with the leukocyte differential and reticulocyte analysis. With the use of these Research Population Data (RPD) parameters several recent publications have shown their usefulness for the diagnosis of malaria (Fourcade et al), sepsis (Chaves ), apoptosis detection (Lab hem 2005) and the diagnosis and differentiation of lymphoptoliferative disorders (Silva M et al)

In order to evaluate the analytical behaviour of these newly described red blood cell and leukocyte morphological parameters in routine bood samples and in the Beckman-Coulter’s calibration and control 5C, we conducted a study to evaluate the paramters’ precision and performance during short and long term sample’s storage:

1. Precision: 10 samples from normal individuals were analyzed 10 times and the CV for each parameter was calculated

2. Short term stability stability at 4C and 22C: 5 normal samples were evaluated from the time of blood drawing until 5 hours later, both at room temperature (22C) and at 4 C

3. Long term stability at 4C: 15 normal samples were evaluated at various times after blood drawing, from 4 hours (which was found to be the best time for sample analysis in the short term stability study, above) up to 77 hours after blood withdrawal.

4. Control and Calibration with 5C: We evaluated the performance of the research parameters in the 5C by running the same batch of 5C control in 5 different counters from 4 different centers, comparing the results with those from 5 normal individuals

5. Stability in a period of time: We have evaluated every week during two months 15 normal samples, recording the temperature and the avergae of all RPD values.

RESULTS

1. Precission: The CV% for the Mean Volume, Conductivity and Scatter of the different leukocyte types was always less than 1%, with an average of 0,6%. The CV% for the Standard Deviation of Volume, Conductivity and Scatter varied between 2.45% and 7.7%, wit an average of 4.9%. The CV% of any SD always being higher than the primary parameter.

2. Short term stability: We observed no significant differences between samples kept at 4C and 22C during the first 5 hours after blood drawing. During the first two hours, however, minor fluctuations in results occurred, always <5%, being preferable to test the samples after blood stabilization, between 2 and 5 hours after withdrawal.

3. Long term stability: The stability of the research parameters after 9 hours is best when the samples are kept at 4C, but the differences are not clinically significant up to 17 hours and, for some parameters, up to 24 hours after blood drawing.

4. The comparison of the RPD research parameters from normal samples and from the Beckman’s 5C control showed good correlation in the different counters and the different centers. When the results from the 5C were higher or lower, the results from the normal samples were concordantly higher or lower respectively, The correlation coefficient was 0.98 for the Mean Volume and 0.92 for the Mean Conductivity

5. The Stability of RPD values was acceptable during the period evaluated (2 m.)with changes lower than 3%.

CONCLUSIONS: The results of the present study show that from the analytical stand point, precission, stability and possibility of calibration, these Research Population data are equivalent to those of other laboratory tests performed by modern instruments.