Abstract
Measuring CD4 counts remains an important component of HIV care. The Visitect CD4 is the first instrument-free low-cost point-of-care CD4 test with results interpreted visually after 40 min, providing a result of ≥350 CD4 cells/mm3 The field performance and diagnostic accuracy of the test was assessed among HIV-infected pregnant women in South Africa. A nurse performed testing at the point-of-care using both venous and finger-prick blood, and a counselor and laboratory staff tested venous blood in the clinic laboratory (four Visitect CD4 tests/participant). Performance was compared to the mean CD4 count from duplicate flow cytometry tests on venous blood (FACSCalibur Trucount). In 2017, 156 patients were enrolled, providing a total of 624 Visitect CD4 tests (468 venous and 156 finger-prick samples). Of 624 tests, 28 (4.5%) were inconclusive. Generalized linear mixed modeling showed better performance of the test on venous blood (sensitivity = 81.7%; 95% confidence interval [CI] = 72.3 to 91.1]; specificity = 82.6%, 95% CI = 77.1 to 88.1) than on finger-prick specimens (sensitivity = 60.7%; 95% CI = 45.0 to 76.3; specificity = 89.5%, 95% CI = 83.2 to 95.8; P = 0.001). No difference in performance was detected by cadre of health worker (P = 0.113) or between point-of-care versus laboratory-based testing (P = 0.108). Adequate performance of Visitect CD4 with different operators and at the point of care, with no need of electricity or instrument, shows the potential utility of this device, especially for facilitating decentralization of CD4 testing services in rural areas.
Highlights
Measuring CD4 counts remains an important component of HIV care
Since the earliest days of HIV treatment and care, measuring CD4 cell counts has been an important component of the continuum of care for adults and children living with HIV
Recommendations for antiretroviral treatment (ART) initiation based on the CD4 level have evolved over time, with World Health Organization (WHO) guidelines arguing for a move to 350 cells/mm3 in 2010, a move to 500 cells/mm3 in 2013 [4, 5], and the removal of the threshold altogether in 2015 [6]
Summary
Measuring CD4 counts remains an important component of HIV care. The Visitect CD4 is the first instrument-free low-cost point-of-care CD4 test with results interpreted visually after 40 min, providing a result of Ն350 CD4 cells/mm. Regardless of the epidemic profile and disease burden, patients with a CD4 count below 350 cells/mm should be prioritized for ART and care [7] This group is at high risk of mortality, opportunistic infections, and cancers related to HIV. In settings where viral load testing is not routinely available (around half of ART patients worldwide), the WHO recommends that a CD4 count, in conjunction with clinical monitoring, should be used to diagnose treatment failure [3]. Despite wide variability and poor precision of CD4 count assessments [9,10,11], flow cytometric methods have provided the gold standard for CD4 monitoring These assays require an electronic instrument, typically with constant power or batteries, and regular equipment maintenance, as well as highly trained technicians and cold-chain management of reagents [12, 13]. Performance of point-of-care CD4 technologies has been acceptable [9, 15], implementation challenges remained due to the need for powered instrumentation, device failures, maintenance requirements, and operator errors [15]
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