[Evaluation of an automatic analyzer of reticulocytes: the Sysmex R-1 000].

The microscopic enumeration of reticulocytes is a tedious assay with poor reproducibility. Its results provide only fragmentory information on the kinetics of erythropoiesis. Thus, attempts have been made for its automation. This study presents results of an evaluation of the first machine exclusively devoted to reticulocyte analysis. The Sysmex R-1 000 uses flow cytofluorometry with argon laser, after precipitation of nucleic acids by auramine-O. The whole study was performed according to ICSH recommendations. At least 2,500 erythrocytes were examined in the microscopic reference technique, after 1 p. cent brilliant cresyl-blue staining. Within and between-batch precision studies gave CV not exceeding 5.46 and 8.72 p. cent respectively for reticulocyte numbers. In dilution study it was shown that no measured result was over 4 p. cent of the expected value, in the range 4-400 x 10(9)/l. There was no significant carry-over in the range tested (35-510 x 10(9)/l). Accuracy testing proved that the significant difference observed when microscopic enumeration was performed in routine conditions disappeared when at least 5,000 erythrocytes were examined. Keeping the samples at 4 degrees C limited the decrease of the reticulocyte number to less than 10 p. cent after 24 hours. Analysis of some particular clinical situations demonstrated the risk of spurious results in case of massive Plasmodium infestation, and the usefulness of obtaining the percentage of newly emerged reticulocytes, i.e. the most fluorescent, for a better estimate of the kinetics of erythrocyte production. This evaluation testifies the quality of the Sysmex R-1 000, and underlines the potential benefit of such analyzers in the equipment of the modern hematology laboratory.