Evaluation of a low-cost method, the Guava EasyCD4 assay, to enumerate CD4-positive lymphocyte counts in HIV-infected patients in the United States and Uganda

Objective: To evaluate the EasyCD4 assay, a less expensive method to enumerate CD4⁺ lymphocytes, in resource-limited settings. Design: Cross-sectional study conducted in the United States and Uganda. Methods: We compared CD4⁺ cell counts obtained on replicate samples from HIV-infected patients by the EasyCD4 assay, a microcapillary flow-based system, and by standard flow cytometry or FACSCount with linear regression and the Bland-Altman method. Results: Two hundred eighteen samples were analyzed (77 in the United States and 141 in Uganda). In the United States, mean ± SD CD4 was 697 ± 438 cells/μL by standard flow cytometry and 688 ± 451 cells/μL by EasyCD4. In Uganda, the mean ± SD CD4 was 335 ± 331 cells/μL by FACSCount and 340 ± 327 cells/μL by EasyCD4. The 2 methods were highly correlated (US cohort, r² = 0.97, slope = 1.0, intercept = -18; Ugandan cohort, r² = 0.92; slope = 0.95; intercept = 23). The mean differences in CD4 cell counts were 9.0 and -4.6 cells/μL for the US and Ugandan cohorts, respectively, and they were not significant in either cohort. In the Ugandan cohort, sensitivity and specificity of the EasyCD4 for CD4 below 200 cells/ μL were 90% and 98%, respectively. Positive predictive value was 96%; negative predictive value was 93%. Conclusions: Our results suggest that EasyCD4 may be used with high positive and negative predictive value in resource-limited settings.