[Evaluation of the blood analyzer Beckman Coulter LH 750: analytic performance, decision rules].

We evaluated the new analyzer Beckman Coulter, an instrument dedicated to the cell blood count (CBC) and to the white blood cell (WBC) differential (including nucleated red blood cells (NRBCs)) over a global one month period, with three purposes: 1) evaluation of the analytical performance (precision, reproducibility, contamination, linearity); 2) accuracy of numerical results, by comparison to the laboratory instrument (CBC and WBC diff) or to the blood smear (NRBCs, low platelets); 3) evaluation, in terms of sensitivity and specificity, a set of abnormality messages built from the suspect flags and a few quantitative abnormalities. The analytical performances were found satisfactory. The WBC and platelet ranges of linearity were wider than in the GEN.S, as stated in the system specifications. However, the lack of adequate biological material made impossible the study of the whole mentioned linearity range. The accuracy of the CBC and differential parameters, as well as of reticulocytes, was studied with the Coulter GEN.S as reference instrument. The coefficients of correlation and the regression lines showed that the LH 750 results were similar to the GEN.S results. Furthermore, samples with thrombocytopenia and circulating NRBCs were evaluated and compared to the result obtained with microscopic lecture. The results showed a good relationship between platelets results given by the GEN.S and manual count leading to appropriate decision of transfusion. The correlation between GEN.S and manual count of NRBC was estimated as satisfactory. We used the LH 750 software to create conditional rules on the basis of qualitative and quantitative criteria, in order to define and enter a message system for detection of abnormalities. Our study showed that such a system flagged 95.7% of morphological abnormalities with a rate of unnecessary slide review (absence of any morphological abnormality on the blood smear) estimated at 8.3%. Furthermore, in 86% of the abnormalities studied, the relevant message was triggered. The Beckman Coulter LH 750 thus appeared as suitable in terms of validation efficiency.