Automated white blood cell counts in cerebrospinal fluid using the body fluid mode on the platform Sysmex XE-5000

Abstract

Background. The Sysmex XE-5000 offers automated quantification of red blood cells and white blood cells (WBCs) in body fluids, with differentiation of polymorphonuclear cells (PMNs) and mononuclear cells (MNCs). Methods. We evaluated automated WBC counting in cerebrospinal fluid (CSF) using the body fluid mode on the Sysmex XE-5000, comparing it with flow cytometry as the reference method, and also with manual counting by microscopy. Experimental analysis for linearity and limit of detection was performed by diluting isolated WBCs in cell-free CSF. To study the ability to discriminate between PMNs and MNCs, samples were spiked using MNCs separated from peripheral blood. Comparison of WBC counts between a counting chamber and the XE-5000 was performed for 198 CSF samples. Results. In the experimental set-up, within-run (CV 19%) and between-day imprecision (CV 15.3%) in quantitating total number of WBC on XE-5000 was acceptable for WBC counts ≥ 25 × 106/L. Compared with expected cell counts, mean bias was + 2.6% for flow cytometry, + 5.5% for XE-5000 and − 73.2% for manual counting. Differentiation between PMNs and MNCs was in concordance with flow cytometry. In comparisons of clinical CSF samples, overall agreement between the XE-5000 and manual counting was observed in 81% of the samples, but mean difference in WBC differentiation was higher for PMN (51.1 × 106/L) than for MNC (7.95 × 106/L). Conclusion. Despite limited precision at low WBC counts, XE-5000 could be a favourable alternative to the labour-intensive, time-consuming and less reliable manual counting and cuts turnaround times in routine CSF-based diagnosis.