Leukocyte counts in cerebrospinal fluid with the automated hematology analyzer CellDyn 3500 and the urine flow cytometer UF-100

Background: The counting of leukocytes and erythrocytes in cerebrospinal fl uid (CSF) is still performed microscopically, e.g., using a chamber in most laboratories. This requires sufficient practical experience, is time-consu ming, and may constitute a problem in emergency diagnostics. Specific autom ated systems for CSF cell counting are not available at present. Methods: We tested the hematology analyzer CellDyn 3500 (CD) and the urine flow cytometer UF-100 (UF), which are not designed for CSF analysis. We stu died >104 samples with both analyzers, and the counts obtained were compare d with the reference method (Fuchs-Rosenthal chamber). Results: Good linearity in the medically relevant range of 15 x 10(6) to 10 00 x 10(6) leukocytes/L and a high degree of within-run accuracy were seen for both analyzers. Cell counting on the UF was excellent, especially when low cell counts were encountered (CV, 4.9% compared with 28% observed for t he CD). Method comparison showed that identical results could be detected f or a majority of the count pairs. For a few samples, there was a discrepanc y between the results from the analyzers and the counting chamber. In most cases, these were CSF samples containing a high proportion of lymphocytes. For these samples, the CD result led to a false-positive high leukocyte cou nt, and on the UF these cells were not allocated to the leukocyte populatio n, thus leading to false-negative counts. Conclusions: Both analyzers should not be used for CSF cell counting in all cases at present. However, once the technical and software problems have b een solved, routine use of the two analyzers for CSF analysis should be ser iously contemplated. (C) 2000 American Association for Clinical Chemistry.