New BD FACSCount™ CD4 reagent system for simultaneous enumeration of percent and absolute CD4 T‐lymphocytes in HIV‐1‐infected pediatric patients

Background Absolute CD4+ T‐lymphocyte counts are used in the initiation and monitoring of antiretroviral therapy in HIV‐infected patients. Becton Dickinson's (BD) FACSCount™ system was introduced 12 years ago as a dedicated instrument for enumeration of absolute CD4+ T‐lymphocytes. However, this system does not provide percent CD4+ T‐lymphocyte that is the required monitoring parameter in pediatric patients. We evaluated a new BD FACSCount CD4 software and reagents for simultaneous percent and absolute CD4+ T‐lymphocytes in HIV‐infected blood. Methods Percent and absolute CD4+ T‐lymphocytes in 149 HIV‐infected blood samples were determined using a new FACSCount system. Results of percent and absolute CD4+ T‐lymphocytes were compared between the dual‐platform (DP) method, using BD FACScan™ flow cytometer plus hematology analyzer and the standard FACSCount system. Correlation and agreement were analyzed using linear regression and Bland–Altman analysis. Results Percent CD4+ T‐lymphocyte values obtained from the new FACSCount system correlated well with DP FACScan method ( r 2 = 0.977, P < 0.0001). Mean bias was only −0.36% [limit of agreement (LOA): −2.52% to +1.80%] and percent similarity was 101.36%. For absolute CD4+ T‐lymphocyte, the new system correlated highly with standard FACSCount system ( r 2 = 0.986, P < 0.0001), with a percent similarity of 98.2. Mean bias was +3.39 cells/μl with LOA of −52.53 cells/μl to +59.31 cells/μl. Conclusion This new FACSCount system is a simple and reliable system for enumeration of absolute and percent CD4+ T‐lymphocytes. Having one system giving both results should reduce the cost and thus increase access to CD4 testing for pediatric and adult patients. © 2008 Clinical Cytometry Society