Early Diagnosis of HIV-1 and HIV-2 Using Cobas HIV-1/HIV-2 Qualitative Test

A Novel Qualitative Nucleic Acid Amplification Test for Plasma, Serum, and Dried Blood Spot Specimens

Lucia Hans, MB BCh, FCPath; Nicole von Allmen, PhD; Anke Edelmann, PhD; Jörg Hofmann, PhD; Alex Y. Nilsson, PhD; Christian O. Simon, PhD; Britta Seiverth, PhD; Peter Gohl, PhD; Sergio Carmona, PhD

Disclosures

J Acquir Immune Defic Syndr. 2021;87(5):1187-1195. 

In This Article

Background

Worldwide, there are an estimated 36.7 million people living with HIV and an additional 1.8 million new infections occur annually.[1] Only approximately 70% of all people living with HIV know their HIV status,[1] well short of the target of 90% set by The Joint United Nations Programme on HIV/AIDS.[2] After infection with HIV, there is a 3- to 4-week window, called acute HIV, before a serological response is detectable.[3–5] Fourth-generation tests that detect p24 protein antigen can identify infected individuals earlier in the course of the disease, at around 2–3 weeks after infection.[6] By targeting HIV RNA or DNA, nucleic acid amplification tests (NATs) can further reduce this window to about 10 days.[3,6]

Between 30% and 70% of individuals with acute HIV infection seek health care for symptoms that occur shortly after HIV infection.[7,8] An early HIV diagnosis allows for rapid treatment of the acute infection, which limits the size and genetic diversity of the viral reservoir, protects cells from persistent infection, and may enhance posttreatment control.[9–12] Detecting recently acquired infections is increasingly viewed as a core component of preventing horizontal and vertical transmission of HIV.[3] Although empirical evidence is sparse, modeling data suggest that as many as half of HIV infections in adults are acquired from people with acute or early HIV.[3,13] Similarly, rates of HIV infection in infants are severalfold higher than those in pregnant women with acute HIV compared with those with an established infection,[14] and acute HIV in pregnant women may account for as much as one-quarter of HIV infections in children.[15]

Although HIV-1 is responsible for most HIV infections, the prevalence of HIV-2 remains considerable in West Africa, and the strain has been reported worldwide.[16,17] Differentiating between HIV-1 and HIV-2 is important, given the varying clinical courses of these infections, the intrinsic resistance of HIV-2 to several antiretroviral drugs, and the need for different tests to monitor viral loads.[16,18–20] The World Health Organization (WHO) recommends that tests should be performed to distinguish HIV viral type in settings where HIV-2 is present.[21] The US Centers for Disease Control and Prevention and the European guidelines on HIV testing go further, stipulating that it is necessary to differentiate between HIV-1 and HIV-2 in all HIV-positive patients.[6,22,23] Many assays are limited to the identification of one HIV type, and those specifically designed for dual identification have high levels of serological cross-reactivity. In an assessment by WHO, cross-reactivity ranged from 3% to 57% with different assays and usually results in HIV-2 being overdiagnosed.[24–26] Importantly, both WHO and the US Food and Drug Administration require that screening and confirmatory serological tests must include detection of antibodies to both HIV-1 and HIV-2.

In addition to the global burden of HIV in adults, each year, an estimated 180,000 infants and young children acquire HIV.[27] Diagnosing HIV in infants and young children is challenging because antibodies from an HIV-infected mother pass through the placenta and through breastfeeding, making serological testing unreliable in children younger than 18 months.[28,29] In this age group, WHO recommends virological testing, using NAT or similar assays, to diagnose HIV, with testing performed at birth and at 4–6 weeks, and to confirm a positive serological test between 9 and 18 months.[30] At present, however, only about half of all HIV-exposed infants are tested within the first 2 months of life.[31] This is concerning because early diagnosis and treatment in infants can reduce HIV-related mortality and disease progression by 75% and enhance long-term cognitive outcomes, among other benefits.[32,33] Many strategies for increasing levels of HIV testing in children are based on the use of dried blood spots (DBSs) collected from finger pricks or other samples.[30,34] DBSs facilitate the decentralization of specimen collection, whereas maintaining high throughput at centralized laboratories.[35] Aside from DBSs' role in HIV testing in children, it has a broad range of applications within the HIV field, including monitoring antiretroviral treatment, diagnosing acute HIV infection, and estimating incidence in surveillance studies.[35,36]

The cobas HIV-1/HIV-2 qualitative test (cobas HIV-1/2 Qual; Roche Molecular Systems, South Branchburg, New Jersey.) for use on the cobas 6800/8800 Systems is the first CE-marked polymerase chain reaction (PCR) assay for the qualitative detection and differentiation of HIV-1 and HIV-2. This study evaluates the analytical and clinical performance of the assay using adult plasma and serum samples and pediatric DBS specimens.

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