Validation of Microcapillary Flow Cytometry for Community-Based CD4+ T Lymphocyte Enumeration in Remote Burkina Faso

Abstract

Background: CD4+ T lymphocyte enumeration plays a critical role in the initiation and monitoring of HIV-infected patients on antiretroviral therapy. There is an urgent need for low-cost CD4+ enumeration technologies, particularly for use in dry, dusty climates characteristic of many small cities in Sub-Saharan Africa.

Design: Cross-sectional study.

Methods: Blood samples from 98 HIV-infected patients followed in a community HIV clinic in Ouahigouya, Burkina Faso were obtained for routine CD4+ T lymphocyte count monitoring. The blood samples were divided into two aliquots, on which parallel CD4+ measurements were performed using microcapillary (Guava EasyCD4) and dedicated (Becton Dickinson FACSCount) CD4+ enumeration systems. Spearman rank correlation coefficient was calculated, and the sensitivity, specificity and positive predictive value (PPV) for EasyCD4 <200 cells/µL were determined compared to the reference standard FACSCount CD4 <200 cells/µL.

Results: Mean CD4 counts for the EasyCD4 and FACSCount were 313.75 cells/µL and 303.47 cells/µL, respectively. The Spearman rank correlation coefficient was 0.92 (p<0.001). Median values using EasyCD4 were higher than those with the FACSCount (p=0.004). For a CD4<350 cells/uL, sensitivity of the EasyCD4 was 93.9% (95%CI 85.2-98.3%), specificity was 90.6% (95% CI 75.0-98.0%), and PPV was 95.4% (95%CI 87.1-99.0%).

Conclusion: Use of the EasyCD4 system was feasible and highly accurate in the harsh conditions of this remote city in Sub-Saharan Africa, demonstrating acceptable sensitivity and specificity compared to a standard operating system. Microcapillary flow cytometry offers a cost-effective alternative for community-based, point-of-care CD4+ testing and could play a substantial role in scaling up HIV care in remote, resource-limited settings.

Keywords: CD4+ count; EasyCD4 assay; Guava Technologies, Inc.,; Low-cost CD4; microcapillary flow cytometry; resource-limited setting..

Fig. (1)

Correlation Analysis of the EasyCD4 assay and FACSCount for cell counts (cells/µL), divided into CD4+ T lymphocyte count by FACSCount <200 cells/µL (red diamonds), 200-350 cells/µL (blue circles), and > 350 cells/µL (black squares). Spearman rank correlation coefficient = 0.92 (P<0.001). The solid line represents the regression line. Mean CD4 counts for the EasyCD4 and FACSCount systems were 313.75 cells/µL and 303.47 cells/µL, respectively.

Fig. (2)

Bland-Altman Plot (n=98, HIV-infected individual whole blood samples) to establish agreement between the EasyCD4 assay and FACSCount for CD4+ T lymphocyte enumeration. CD4+ T lymphocyte count by FACSCount is divided into <200 cells/µL (red diamonds), 200-350 cells/µL (blue circles), and >350 cells/µL (black squares). The solid horizontal line represents the mean difference between the two systems.