Validation of the body fluid module on the new sysmex XN-1000 for counting blood cells in cerebrospinal fluid and other body fluids

Background: We evaluated the body fluid (BF) module on the new Sysmex XN-1000 for counting blood cells. Methods: One hundred and eighty-seven BF samples [73 cerebrospinal fluid (CSF), 48 continuous ambulatory peritoneal dialysis (CAPD), 46 ascites, and 20 pleural fluid] were used for method comparison between the XN-1000 and manual microscopy (Fuchs-Rosenthal chamber and stained cytospin slides) for counting red blood cells (RBCs) and white blood cells (WBCs) (differential). Results: Good agreement was found for counting WBCs (y = 1.06x + 0.09, n = 67, R2 = 0.96) and mononuclear cells (MNs) (y = 1.04x - 0.01, n = 40, R2 = 0.93) in CSF. However, the XN-1000 systematically counted more polymorphonuclear cells (PMNs) (y = 1.48x + 0.18, n = 40, R2 = 0.99) compared to manual microscopy. Excellent correlation for RBCs > 1 × 109/L (y = 0.99x + 116.56, n = 26, R2 = 0.99) in CSF was found. For other fluids (CAPD, ascites and pleural fluid) excellent agreement was found for counting WBCs (y = 1.06x + 0.26, n = 109, R2 = 0.98), MNs (y = 1.06x - 0.41, n = 93, R 2 = 0.96), PMNs (y = 1.06x + 0.81, n = 93, R2 = 0.98) and RBCs (y = 1.04x + 110.04, n = 43, R2 = 0.98). By using BF XN-check, the lower limit of quantitation (LLoQ) for WBC was defined at 5 × 10 6/L. Linearity was excellent for both the WBCs (R2 = 0.99) and RBCs (R2 = 0.99) and carry-over never exceeded 0.05 %. Conclusions: The BF module on the XN-1000 is a suitable tool for fast and accurate quantification of WBC (differential) and RBC counts in CSF and other BFs in a diagnostic setting.

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