Cost savings by reagent reduction in flow cytometry-based CD4+ T cell counts: an approach to improve accessibility for HIV management.

In Thailand, the cost of antiretrovirals has recently been reduced more than 10 fold. Likewise strategies for a cost reduction in laboratory monitoring are warranted. This study was designed to explore if the most expensive reagent in flow cytometry based CD4+ cell monitoring, the CD4+/CD8+ monoclonal antibodies, can be reduced without a loss of accuracy. Blood samples from 55 HIV seronegative (HIV-) and 76 HIV+ subjects were analyzed for %CD4+ and %CD8+ T cells using a two color monoclonal antibody panel (BD Biosciences, CA, USA) with 3 different amounts of the recommended reagents for staining: 1) standard, 2) half, and 3) one-fourth. A significant Spearman correlation of 0.987 was shown for the % CD4+ T cell test results for one half as well as one-fourth of the recommended amount compared to the standard staining according to the manufacturer's instruction (p < 0.0001). For the % CD8+ T cell test results, the correlation between the standard and the half or one-fourth reduced staining was 0.972 (p < 0.0001). Bland-Altman analysis showed no significant bias between the results from one half or one-fourth of the recommended amount versus the standard. The sensitivity and specificity of the two methods at the CD4+ T cell count cut-off of 200 cells/microl were 93% and 100%; and 96% and 99%, respectively. Our study indicates that a reduction of the reagents to half or one-fourth of the amount recommended by the manufacturer was still able to generate reliable results for CD4+ and CD8+ T cell counts. Such an approach will significantly reduce the cost of CD4+ monitoring for resource limited settings where a flow cytometer is available.