Assisted partner services for people who inject drugs in Kenya boost HIV testing and aid linkage to care

Assisted partner services, which contact partners of people with HIV and invite them for testing, are highly effective in diagnosing people unaware of their HIV status and offer a promising model for reaching the partners of people who inject drugs, a study carried out in Kenya has found. The study findings are published in the May edition of Lancet Global Health.

Assisted partner services provide testing and linkage to care for the partners of people who have already tested positive for HIV. These types of services are sometimes also referred to as partner notification, contact tracing or index testing.

A cluster-randomised trial carried out in Kenya previously showed that assisted partner services raised the rate of HIV testing fivefold compared to voluntary notification of partners by people who had recently received a positive test result.

The partners of people who inject drugs have a high risk of acquiring HIV and hepatitis C through sharing of injecting equipment or sexual contact. The prevalence of both infections is higher in people who inject drugs than the rest of the population and people who inject drugs are less likely to volunteer information about their drug-using activity, or their partners, outside settings that provide non-stigmatising services and support for drug users.

People who inject drugs are especially marginalised in sub-Saharan Africa, where harm reduction services such as needle and syringe exchange are limited. Yet HIV prevalence of 18% has been observed among people who inject drugs in Kenya, compared to just over 3% in the general population.

To evaluate whether assisted partner services could reach the partners of people who inject drugs in Kenya, researchers from the University of Washington, Seattle and the Kenya National AIDS Control Programme carried out a prospective cohort study between 2018 and 2021 in which they contacted the sexual partners or needle-sharing contacts of people with HIV who inject drugs at eight sites operated by harm reduction services in Nairobi, Mombasa and the coastal region.

Index participants (people with HIV) were identified by clinicians and peer support workers and invited to take part in the study. All participants underwent rapid testing for hepatitis C antibodies and had blood samples taken for HIV and hepatitis C viral load testing. The study recruited 989 index participants, evenly split between men and women. Eighty-one percent were taking antiretroviral treatment and 68% of all participants were virally suppressed. Sixteen percent had hepatitis C antibodies, 7% had hepatitis C viraemia and 3% had previously received direct-acting antiviral treatment for hepatitis C.

Seven percent of index participants had shared needles in the past month and 11% had shared injecting equipment. On average, index participants injected drugs 60 times a month and reported a median of two sexual encounters in the previous month (56% reported condom use during their last sexual intercourse).

Index participants were asked to provide information on all sexual and injecting partners over the past three years, including contact details. Peer educators attempted to contact partners in person or by phone and invited them to take part in a research study, without disclosing that they had been named by an index participant. Those who did not want to participate were encouraged to test for HIV.

Partners were eligible for inclusion in the study if they were aged 18 or over and had had sexual intercourse or injected drugs with the index partner in the past three years, irrespective of whether they had shared needles. The study recruited 3323 unique individuals, representing 4597 named partners of index participants, out of a total of 4705 named partners.

Testing showed that 597 (18%) of partners were HIV-positive, but only 91 were newly diagnosed, meaning that just over ten people needed to be interviewed and tested in order to diagnose one person who was unaware that they were living with HIV. Of those who already knew their HIV status, 71% were on antiretroviral treatment and virally suppressed. It was necessary to interview and test four partners to find one person who was not virally suppressed, either because they were unaware of their HIV status, not on antiretroviral treatment or not virally suppressed despite treatment.

For injecting partners specifically, it was necessary to interview and test six partners to find one person who was not virally suppressed, either because they were unaware of their HIV status, not on antiretroviral treatment or not virally suppressed despite treatment. For sexual partners, it was necessary to interview and test 17 partners to find one person who was not virally suppressed, either because they were unaware of their HIV status, not on antiretroviral treatment or not virally suppressed on treatment.

Overall, 12% of partners were positive for hepatitis C antibodies and just over half of these (6% of all partners) had hepatitis C viremia (people who spontaneously clear hepatitis C infection will retain antibodies). It was necessary to interview and test four partners to find one person who required treatment for hepatitis C.

Six months after enrolment, 72% of partners not on antiretroviral treatment at study entry were taking ART and 88% of those who had been taking antiretroviral treatment at study entry were still on treatment.

In an accompanying editorial comment, researchers from Malawi and the University of North Carolina point to the high rates of case-finding achieved in this study as evidence that assisted partner services are appropriate and effective for people who inject drugs and their partners.

They also draw attention to the high rates of enrolment and retention in treatment among people diagnosed with HIV during the study. “Although assisted partner services are typically characterised as an HIV testing intervention, this study reinforces their role in linkage to care,” they comment.

They say that understanding how the peer supporters were trained and supervised could allow other programmes to achieve similar outcomes.