Automated Cell Counting in CSF Diagnostics Revisited-Friend or Foe?

Abstract

Background/Objectives: The gold standard for cerebrospinal fluid leukocyte counting is manual counting in a Fuchs-Rosenthal chamber. Recent advances in automated body-fluid-counting systems, offering a time- and labor-saving solution, are challenging this dogma. Yet, the equivalence of diagnostic accuracy is still debated in the community. Methods: We compared manual and automated cell counting of cerebrospinal fluid samples of lumbar punctures and extraventricular drains with both low and high leukocyte counts, shedding light on the variability of results between man and machine. Results: Automated and manual cell counting showed a strong correlation across all samples, particularly in the subgroup of patients with fewer than 20 cells/µl, where outliers could become especially clinically relevant. Conclusions: We found the automated counting system to be highly accurate and not lacking in diagnostic sensitivity even at low cell counts, making it a powerful tool when used in the right clinical setting.

Keywords: CSF diagnostics; Fuchs–Rosenthal counting chamber; Sysmex XN-9000; automated cell counting; cerebrospinal fluid.

Figure 1

High correlation of CSF leukocyte counts assessed with manual and automated counting. Linear regression analysis with plot of the 95% confidence interval (dotted lines).

Figure 2

Subgroup of patients with low CSF cell counts (<20 cells/µL). Close correlation of manual and automated cell counts. Linear regression analysis with plot of the 95% confidence interval (dotted lines) (A). Bland–Altman analysis of the same collective to evaluate the agreement between the two different methods of measurement (B). The scattering of the differences around 0 indicates that there is no consistent difference between the methods. Additionally, most differences fall within the 95% limits of agreement suggesting interchangeability.