EVALUATION OF THE FACSCOUNT, TRAX CD4 AND DYNABEADS METHODS FOR CD4 LYMPHOCYTE DETERMINATION

A study to evaluate the performance of the FACScount, TRAx CD4 and Dyn abeads methods for the determination of CD4(+) T lymphocyte subset lev els was conducted in Tanzania as part of a World Health Organization ( WHO) collaborative multicenter field evaluation of alternative methodo logies for the enumeration of CD4(+) T lymphocytes. The objective was to compare the performance of these alternative methods in a developin g country setting, against that of flow cytometry as the reference sta ndard. T lymphocyte subset levels were determined in 91 HIV seronegati ve and 98 HIV-1 seropositive adults using the three alternative method s. CD4(+) and CD8(+) T lymphocyte counts were determined by all method s except for TRAx CD4 enzyme linked immunosorbent assay (ELISA) which measures CD4(+) T lymphocyte levels only, Linear regression analysis w as done to correlate the counts obtained by the alternative methods to those obtained by flow cytometry, The overall correlation coefficient s of FACScount and Dynabeads CD4(+) and CD8(+) T lymphocyte counts wit h those of flow cytometry were high (r > 0.9). A lower correlation (r = 0.631) was obtained when TRAx CD4(+) ELISA counts were compared to t hose of the reference method, These results show that two of these alt ernative methodologies are suitable for the determination of CD4(+) an d CD8(+) T lymphocyte counts with the use of African blood samples, Si nce the methods are simpler and cheaper than flow cytometry, they prov ide an alternative option for the enumeration of T lymphocyte subsets in laboratories with limited facilities.