Technical performance evaluation of the MyT4 point of care technology for CD4+ T cell enumeration

Abstract

Objective: Though absolute CD4+ T cell enumeration is the primary gateway to antiretroviral therapy initiation for HIV-positive patients in all developing countries, patient access to this critical diagnostic test is relatively poor. We technically evaluated the performance of a newly developed point-of-care CD4+ T cell technology, the MyT4, compared with conventional CD4+ T cell testing technologies.

Design: Over 250 HIV-positive patients were consecutively enrolled and their blood tested on the MyT4, BD FACSCalibur, and BD FACSCount.

Results: Compared with the BD FACSCount, the MyT4 had an r2 of 0.7269 and a mean bias of -23.37 cells/µl. Compared with the BD FACSCalibur, the MyT4 had an r2 of 0.5825 and a mean bias of -46.58 cells/µl. Kenya currently uses a CD4+ T cell test threshold of 350 cells/µl to determine patient eligibility for antiretroviral therapy. At this threshold, the MyT4 had a sensitivity of 95.3% (95% CI: 88.4-98.7%) and a specificity of 87.9% (95% CI: 82.3-92.3%) compared with the BD FACSCount and sensitivity and specificity of 88.2% (95% CI: 79.4-94.2%) and 84.2% (95% CI: 78.2-89.2%), respectively, compared with the BD FACSCalibur. Finally, the MyT4 had a coefficient of variation of 12.80% compared with 14.03% for the BD FACSCalibur.

Conclusions: We conclude that the MyT4 performed well at the current 350 cells/µl ART initiation eligibility threshold when used by lower cadres of health care facility staff in rural clinics compared to conventional CD4+ T cell technologies.

Figure 1. Linear regression (a, c, e) and Bland-Altman (b, d, f) analyses of absolute CD4+ T cell counts between the MyT4 and BD FACSCount (a and b); the MyT4 and BD FACSCalibur (c and d); and BD FACSCount and BD FACSCalibur (e and f).