Determination of CD4+ and CD8+ lymphocytes with the cytosphere assay: a comparative study with flow cytometry and the immunoalkaline phosphatase method.

The proportion and absolute numbers of CD4+ and CD8+ lymphocytes in peripheral blood were determined using a new manual method, the cytosphere assay (CA). This method uses small latex beads coated with monoclonal antibodies directed against the CD4 and CD8 receptors, respectively. The CA was compared with two other methods for determination of T lymphocyte subsets, flow cytometry (FC) and the immunoalkaline phosphatase (IA) method, by testing HIV-seropositive and HIV-seronegative samples from Denmark (44) and Ivory Coast (79). For HIV-seropositive samples, both the proportion and the absolute number of CD4+ lymphocytes determined by CA showed a good correlation with results obtained by FC (correlation coefficients were 0.92 and 0.74 in Denmark and The Ivory Coast, respectively) and IA (correlation coefficients were 0.94 and 0.66 in Denmark and The Ivory Coast, respectively). However, for HIV-seronegative samples the corresponding correlation coefficients were low. CD4% determinations deviated more from FC counts at higher CD4 counts than at lower levels for both seronegative and seropositive individuals. In conclusion, the CA performed best for samples from HIV-infected individuals. Before a more general utilization of the method, it is necessary to improve its repeatability and standardize its performance at all levels of CD4+ T cells.