Effectiveness of Human Immunodeficiency Virus Index Testing: A Global Scoping Review

INTRODUCTION

New human immunodeficiency virus (HIV) infections and acquired immunodeficiency syndrome (AIDS)-related deaths in India dropped by 44% (1.2 lakhs to 68,450) and 80% (1.6 lakhs to 35,870), respectively, between 2010 and 2023,^[1] both outclassed the global average; however, 185 Indians were infected each day in 2023.^[2] HIV prevention efforts need to be accelerated if India is to meet the sustainable development goal (SDG) 3.3 target of ending AIDS as a public health threat by 2030. To achieve SDG 3.3, early diagnosis of HIV and prompt linkage of the diagnosed case to anti-retroviral treatment (ART), along with prevention of new HIV infections, is the key.

In India, 81% of the people living with HIV (PLHIV) know their status, and 70% of PLHIV are on ART, implying that many with HIV were unaware of their status.^[1] There is an increasing focus on HIV testing in high-risk or key groups such as people who inject drugs, men who have sex with men (MSM), and female sex workers. However, sexual partners of index-positive clients are an important population that has largely been ignored due to the reluctance to disclose information about their sexual partners, stigma, and social barriers. This high-risk group establishes a “pivotal point” that must be reached to achieve HIV control, thereby attaining the 1^st 95% of the 95-95-95 initiative.^[3]

The Government of India introduced newer strategies that reinforce these targets under the National AIDS Control Program (NACP-V). One of these strategies is HIV index testing, which the National AIDS Control Organization introduced in a campaign mode. The campaign was from April 15^th, 2024, to October 15^th, 2024, with pan-India implementation. The first phase was from April 15^th, 2024, to July 15^th, 2024, in all districts having ART centers; whereas the second phase, from July 15^th, 2024, to October 15^th, 2024, included the remaining districts.^[4]

Index testing is an evidence-based, World Health Organization (WHO)-endorsed form of contact tracing. It involves identifying and testing partners as well as biological children who are at risk of vertical transmission of HIV. It is a targeted approach to identify undiagnosed infections and improve diagnosis rates.^[5] Index testing focuses on individuals diagnosed with HIV, referred to as the “index case.”^[6] These individuals are offered counseling to disclose their status to their sexual partners, children, and other close contacts.^[7] Healthcare providers then work with the index case to encourage these contacts to undergo HIV testing. This strategy leverages existing connections and overcomes the stigma associated with routine testing.^[8]

Early diagnosis allows PLHIV to initiate ART, which suppresses the virus and reduces the risk of transmission.^[9] Late diagnosis of HIV is an important factor associated with HIV-related morbidity and mortality. Early HIV diagnosis has benefits on individual and population levels.^[10] At an individual level, it significantly enhances quality of life by enabling timely access to ART, which prevents opportunistic infections, reduces transmission risk, and prolongs life expectancy. Knowing HIV status empowers individuals to make informed decisions about their health. At a population level, it significantly reduces new infections, strengthens healthcare systems, and stimulates economic growth.

This scoping review was carried out with the research question “How effective is Index case testing in the uptake of HIV testing and counselling services (HFS), diagnosing partners, and linking them to care?”

METHODS

This scoping review adhered to PRISMA-ScR and Arksey and O’Malley’s guidelines.^[11] A search for relevant studies was carried out in the database PubMed, and an additional search was done in Google Scholar. The search was first performed using MeSH terms. The terms “HIV,” “AIDS,” “index cases,” “HIV Care,” “linkage to care,” “HIV partner testing,” “HIV contact,” “global,” “HIV care continuum,” and “Index testing” were among those used [Table 1]. The WHO and US Centers for Disease Control and Prevention websites were also checked for information about the HIV and AIDS program and operating procedures. The Mendeley software was then used to import relevant records and eliminate duplicate documents. Following that, full-text papers were filtered per the eligibility criteria listed in Table 1. To acquire more data, cross-references were gathered from the appropriate papers.

Search Results

A total of 396 records were initially identified through database searching. The 343 unique records were screened after removing 53 duplicates. The articles were assessed for inclusion criteria, and ultimately, 7 records were found relevant, and 3 articles were selected from back-referencing the included articles, resulting in 10 final studies [Figure 1].

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Figure 1:

Preferred reporting items for systematic reviews and meta-analyses (PRISMA) flowchart for inclusion of study articles.

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RESULTS

DISCUSSION

This review aligns with previous studies by the WHO and the Joint United Nations Programme on HIV/AIDS (UNAIDS), which emphasize the usefulness of index testing in recognizing hidden reservoirs of HIV within social networks.^[23,24] The prevalence rates observed among partners and children in this review (51% for partners and 4.0–5.8% for children) are comparable to those reported in other studies (35–62% for partners and 4–18% for children).^[25] This consistency strengthens the evidence base for the strategy’s ability to detect undiagnosed infections and contribute to achieving targets.

The studies found high acceptance rates for index testing among PLHIV clients, like Edosa et al.^[6] and Kumar et al.^[26] This suggests a willingness among PLHIV to participate in efforts to prevent onward transmission within their social circles. This review aligns with Mushamiri et al., demonstrating the effectiveness of community-based outreach strategies using CHWs to reach geographically dispersed populations.^[27] The observed improvement in linkage to care among those diagnosed through index testing is also consistent with Oljira et al., who reported a higher rate of ART initiation among partners identified through this approach.^[28] These findings suggest that index testing is not only feasible and acceptable but also holds promise for improving care cascades by facilitating earlier access to treatment.

The present review highlights the potential of index testing to reach diverse populations at risk for HIV infection, including children, adolescents, and MSM.^[13,20] The inclusion of MSM populations in this review adds to the growing body of evidence suggesting the strategy’s utility in reaching groups often facing social stigma and barriers to healthcare access. This review identified challenges like those reported in previous studies, including the need for specialized training for healthcare workers on communication and counseling skills, particularly for addressing disclosure concerns.

CONCLUSION AND GLOBAL HEALTH IMPLICATIONS

Through the evidence presented by this scoping review, there is no doubt that index testing is a high-yielding strategy to fast-track the identification of new cases of HIV and to sustain the high levels of linkages to ART. It is specifically effective in increasing the detection and testing of biological children. This is a welcome and much-needed strategy to cater to the high-risk/key population where HIV remains focused, but to include it in NACP-V, the various limitations cited above need to be taken care of. Without targeted intervention offering HIV index testing services to key population clusters, including sexual partners, it will be a challenge to end HIV/AIDS by 2030.