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Clinical and Vaccine Immunology, March 2007, p. 293-298, Vol. 14, No. 3
1071-412X/07/$08.00+0     doi:10.1128/CVI.00416-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Evaluation of the Partec Flow Cytometer against the BD FACSCalibur System for Monitoring Immune Responses of Human Immunodeficiency Virus-Infected Patients in Zimbabwe

National Microbiology Reference Laboratory (NMRL), Harare,¹ African Institute of Biomedical Science and Technology, Harare,² Connaught Clinic, Harare,³ COMFORCE Corporation, Centre for Disease Control (CDC) Zimbabwe, Harare, Zimbabwe⁴

Received 6 November 2006/ Returned for modification 4 January 2007/ Accepted 9 January 2007

A single-platform volumetric flow cytometer, the Partec Cyflow SL_3, was evaluated against a BD FACSCalibur/Sysmex XT1800i dual platform for measuring CD4⁺ lymphocytes, total lymphocytes, and the percentage of CD4 lymphocytes in whole-blood samples for monitoring the immune systems of human immunodeficiency virus (HIV)/AIDS patients. Statistical analyses for precision, correlation, and agreement were performed. Coefficients of variation (CV) of 5.8, 4.6, and 3.9% were obtained for low, medium, and high CD4⁺ cell counts, respectively, using the SL_3, and CV of 3.7, 4.0, and 0.94 were obtained for the same categories, using the BD FACSCalibur. Significant correlations (P < 0.005) between the two assays for CD4 counts, total lymphocyte counts, and percentages of CD4 were obtained, with correlation coefficients of 0.99, 0.96, and 0.99, respectively (n = 229). Using the Bland-Altman plot, mean biases of –18 cell/µl (95% confidence interval (CI); –91 to 54 cells/µl), –0.8% (95% CI; –3.6 to 2%), and –36.8 cells/µl (95% CI; –477 to 404 cells/µl) were obtained for comparisons of CD4 counts, percentages of CD4 cells, and total lymphocyte counts, respectively. The effects of the age of the samples on the three parameters were also analyzed by comparing results from the same samples analyzed at 6, 24, and 48 h after collection. The correlation coefficients for comparisons among different time points for the same machine and among all the time points for the two different machines were greater than 0.90. These data showed that the Partec Cyflow SL_3 assay is comparable to the BD FACSCalibur/Sysmex XT1800i dual-platform method for measuring the amount of CD4⁺ cells and total lymphocytes and the percentages of CD4 cells in blood samples for the purpose of monitoring HIV/AIDS patients.

Published ahead of print on 31 January 2007.