White blood cell count in biological fluids: development and evaluation using the automated particle-analysis DxU^Ⓡ...

Cytological analysis of serous fluids is critical for the diagnosis and therapeutic management of patients. The "gold standard" for cell counting remains manual microscopic counting which is time-consuming and requires skilled and experienced personnel.

Over an 8-month period, we assessed the performance of automated DxU^Ⓡ Iris instrument and compared its results with manual microscopic method.

From June 2023 to March 2024, all serous fluids (synovial fluid (SF), peritoneal fluid (PF), pleural fluid (PLF), ascitic fluid (AF), pericardial fluid (PCF), and peritoneal dialysis fluid (PDF)) were included in this study. White blood cell (WBC) counts were performed manually by microscopic method and simultaneously with the DxU^Ⓡ Iris. For automated analysis, the sample dilution was adjusted according to the appearance of the specimen. Hyaluronidase crystals were added to viscous SF.

A total of 739 body fluids were included: 150 SF, 200 PF, 200 PLF, 150 AF, 33 PCF, and 6 PDF. The agreement between the automated method and the manual reference showed a high correlation, with R² values of 0.943 for SF, 0.908 for PF, 0.756 for PLF, 0.992 for AF, 0.968 for PCF and 0.954 for PDF. In addition, results for body fluid samples from oncologic patients showed no difference between both methods.

The DxU^Ⓡ Iris appears to be a promising alternative to the gold standard for cytological analysis of puncture fluids, including in oncology patients. Its implementation, especially for hyaluronidase pre-treated samples, could effectively replace the time-consuming and tedious optical analysis in routine practice.