The diagnostic performance of different automated hemocytometers for white blood cell (WBC) enumeration of peritoneal fluids was com-pared with manual microscopy analysis.
The term ascites is conventionally used for designating the accumulation of fluid in the peritoneal cavity and the presence of elevate numbers of WBCs and polymorphonucleated leukocytes (PMNs) is pivotal to diagnose spontaneous bacterial peritonitis (SBP).
Scientists at the Academic Hospital of Parma (Italy; www.ao.pr.it) analyzed 100 peritoneal fluids with manual microscopy and five automated hemocytometers. Manual microscopic analysis was carried out using Nageotte and Fuchs-Rosenthal chambers after staining with Turk’s and May-Grünwald-Giemsa reagents.
The five automated counters were the XE-2100 and XE-500Q (Sysmex; Kobe, Japan; www.sysmex.com): the Advia 2120 (Siemens; Erlangen Germany; www.healthcare.siemens.com); the BC-6800 (Mindray; Mahwah, NJ, USA; www.mindray.com); and the Abbott Sapphire (Abbott Park, IL, USA; www.abbottdiagnostics.com]. The XE-2100 is a flow cytometer, using forward-scattered and side-scattered light, whereas the WBC differential entails a specific nucleic acid dye to measure the cells by side-fluorescent light and side-scattered light. The analysis of WBC as performed on the XE-5000 is with a flow cytometry technique by means of a semiconductor laser and fluorescent measurement.
For manual microscopy the mean values in the 100 peritoneal fluids was 873 WBC/mm3 compared to 943 WBC/ mm3 – for the XE-2100 and 741 WBC/ mm3 for XE-5000. For the Advia 2120, the mean was 741 WBC/ mm3, while for the BC-6800 it was 938 WBC/ mm3 and 782 WBC/ mm3 for the Sapphire. There were no significant differences between the different counts and therefore correlations were highly significant. The agreement between manual analysis and flow cytometry at the diagnostic threshold for septic peritonitis with a count equal to or greater than 1000 WBC/ mm3 was 99% for XE-2100, KE-5000, Advia 2120, BC-6800 and 96% for Sapphire.
The authors concluded that used for routine analysis of body fluids the five hemocytometers tested display acceptable performance for routine screening of peritoneal fluid. Higher correlations with manual microscopy were found for the two Sysmex analyzers although those of the Advia 2120, BC-6800 and Sapphire were still excellent The study was published in the January 2013 issue of the journal Clinical Biochemistry.
Image: The XE-5000 automated analyzer (Photo courtesy of Sysmex).