Enumeration of the absolute CD4 T-lymphocyte count by cell-bead assay.

Background: We have previously developed an alternative approach for undertaking absolute cell counting based upon flow-rate calibration using cell bead (FCB), in which cell bead (CB) can be used as a flow-rate calibration material for generating the absolute microparticle counts. Here, we extended our work of counting CD4+ T-lymphocytes in HIV-infected blood samples with the FCB method.

Methods: CD4+ T-lymphocyte counts in EDTA blood samples from 30 healthy subjects and 80 HIV-1-infected patients were determined using TriTEST reagent. The absolute CD4+ T-lymphocytes were measured by FCB, and the results were compared with the absolute counting by commercial latex bead (CLB) or with flow rate-based calibration method (FR). Statistical correlation and agreement were analyzed using linear regression and Bland-Altman analysis.

Results: There was no significant difference in the absolute number of CD4+ T-lymphocyte counts enumerated by FCB when compared with those two reference methods (CLB and FR). The absolute CD4+ T-lymphocyte counts obtained from FCB method was highly correlated with those obtained from CLB [r(2)= 0.99, y = 1.04x - 12.37, P < 0.001, and mean bias 11.96 cell/microl, limit of agreement (LOA) -57.82 - 81.74 cell/microl], FR method (r(2) = 0.98; y = 0.97x - 3.13, P < 0.001, and mean bias -24.15 cell/microl, LOA -114.44 - 66.13 cell/microl).

Conclusions: The use of FCB is comparable with the use of CLB and FR. This approach showed the effective in reducing cost for generating the absolute CD4+ T-lymphocyte counts. Such an approach should facilitate and ensure the success of the ongoing antiretroviral therapy program in resource-limited countries.