Point-of-care p24 antigen detection for early infant diagnosis of HIV infection: cross-sectional and longitudinal studies in Zambia

Catherine G Sutcliffe,Mark J Fisher,Robert Elghanian,Jane Mutanga,Kara M Palamountain,Philip E Thuma,Mutinta Hamahuwa,Jessica L Schue,Nkumbula Moyo,William J Moss,Abhishek K Agarwal

doi:10.1186/s12879-021-05808-2

Abstract

BackgroundEarly infant diagnosis of HIV infection is challenging in sub-Saharan Africa, particularly in rural areas, leading to delays in diagnosis and treatment. Use of a point-of-care test would overcome many challenges. This study evaluated the validity of a novel point-of-care p24 antigen detection test (LYNX) in rural and urban settings in southern Zambia.MethodsTwo studies were conducted: a cross-sectional study from 2014 to 2015 at Macha Hospital (LYNX Hospital study) and a longitudinal study from 2016 to 2018 at 12 health facilities in Southern Province, Zambia (NSEBA study). In both studies, children attending the facilities for early infant diagnosis were enrolled and a blood sample was collected for routine testing at the central lab and immediate on-site testing with the LYNX test. The performance of the LYNX test was measured in comparison to nucleic acid-based testing at the central lab.ResultsIn the LYNX Hospital study, 210 tests were performed at a median age of 23.5 weeks (IQR: 8.9, 29.0). The sensitivity and specificity of the test were 70.0 and 100.0%, respectively. In the NSEBA study, 2608 tests were performed, including 1305 at birth and 1222 on children ≥4 weeks of age. For samples tested at birth, sensitivity was 13.6% (95% CI: 2.9, 34.9) and specificity was 99.6% (95% CI: 99.1, 99.9). While specificity was high for all ages, sensitivity increased with age and was higher for participants tested at ≥4 weeks of age (80.6%; 95% CI: 67.4, 93.7). Children with positive nucleic acid tests were more likely to be negative by the LYNX test if their mother received antiretroviral therapy during pregnancy (60.7% vs. 24.2%; p = 004).ConclusionsConsidering the high specificity and moderate sensitivity that increased with age, the LYNX test could be of value for early infant diagnosis for infants ≥4 weeks of age, particularly in rural areas where centralized testing leads to long delays. Point-of-care tests with moderate sensitivity and high specificity that are affordable, easy-to-use, and easily implemented and maintained should be developed to expand access to testing and deliver same-day results to infants in areas where it is not feasible to implement nucleic acid-based point-of-care assays.

Highlights

Infant diagnosis of Human immunodeficiency virus (HIV) infection is challenging in sub-Saharan Africa, in rural areas, leading to delays in diagnosis and treatment
One child, who tested positive by the central lab and negative by LYNX, was later found to be receiving antiretroviral therapy (ART) and was excluded from further analysis
The positive and negative predictive values of the LYNX test were 100.0 and 98.3%, respectively

Summary

Introduction

Infant diagnosis of HIV infection is challenging in sub-Saharan Africa, in rural areas, leading to delays in diagnosis and treatment. Early infant diagnosis is challenging, in rural regions of sub-Saharan Africa, as virologic tests must be used and these tests are primarily available in central labs located in a few urban areas. In 2019 only 69% of HIV-exposed infants in eastern and southern Africa and 33% of HIV-exposed infants in western and central Africa were estimated to have received a virologic test by 8 weeks of age [7]. Only 58% of children living with HIV in eastern and southern Africa and 33% of children living with HIV in western and central Africa were receiving antiretroviral therapy (ART) [7]

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