Enumeration of CD4 lymphocytes is essential for the clinical management of HIV-infected patients, but it can be difficult to afford in developing countries. In this study we evaluated a reagent reduction strategy for reducing the cost of enumerating CD4 cell absolute count and percentage using the FACSCalibur flow cytometer (Becton Dickinson). We compared the protocol recommended by the manufacturer with a protocol that used half of the usual amount of CD3/CD4/CD45 monoclonal antibody reagent in 100 samples from HIV-infected patients in a rural hospital in India. The concordance correlation coefficient between the two protocols was 0.976 for CD4 cell count and 0.984 for CD4 cell percentage. We did not find significant bias when performing Deming regression or Bland-Altman analysis. Sensitivity and specificity were 97% and 98.5% for identifying patients with less than 200 CD4 cells/μL, 98.1% and 93.8% for identifying patients with less than 350 CD4 cells/μL, and 100% and 94.7% for identifying patients with less than 25% CD4 cells, respectively. This reagent reduction strategy can be used for reducing the cost of enumerating CD4 lymphocytes in high-volume laboratories from resource-limited settings. 1. Introduction In 2010, it was estimated that 34 million people were living with HIV/AIDS and more than 90% were living in low and middle-income countries . Enumeration of CD4 lymphocytes is essential for the clinical management of HIV-infected people. CD4 lymphocyte count can be used for initiating or stopping prophylaxis against opportunistic infections and for deciding when to initiate antiretroviral therapy against HIV . Immunophenotyping by flow cytometer is the most accepted technology for enumeration of CD4 lymphocytes . The FACSCalibur system (Becton Dickinson Biosciences, CA, USA) is a bench-top flow cytometer widely used in laboratories from developed countries and it is considered as the “gold standard” of CD4 counting . However, the high cost of the reagents can be an important limitation for its use in resource-limited settings. In flow cytometry, monoclonal antibodies are the most expensive part of the reagents used to enumerate the absolute count and percentage of CD4 lymphocytes. The objective of this study is to evaluate a reagent reduction strategy for enumerating CD4 lymphocytes with the FACSCalibur system that used half of the usual amount of monoclonal antibodies. 2. Methods The study was performed in the RDT Bathalapalli Hospital, Andhra Pradesh, India. After giving informed consent, peripheral blood was taken from 100
S. Buranapraditkun, S. Nookhai, S. Ubolyam, S. Sirivichayakul, P. Phanuphak, and K. Ruxrungtham, “Cost savings by reagent reduction in flow cytometry-based CD4+ T cell counts: an approach to improve accessibility for HIV management,” Asian Pacific Journal of Allergy and Immunology, vol. 25, no. 1, pp. 83–89, 2007.