Financial incentives to improve uptake of partner treatment for sexually transmitted infections in antenatal care: a cluster randomised trial in Zimbabwe

Abstract

Background: Partner treatment is an essential component of sexually transmitted infection (STI) case management. We aimed to compare the uptake of partner treatment for STIs within antenatal care in Zimbabwe, with and without the provision of a financial incentive.

Methods: The present cluster randomised trial was embedded within a prospective study (IPSAZ) evaluating point-of-care STI screening among pregnant women in Harare, Zimbabwe. Any pregnant woman attending one of two study clinics for antenatal care was eligible for participation in the IPSAZ study. For the current embedded trial, the study population was those women enrolled and screened in the IPSAZ study who were diagnosed with a curable STI or treated for an STI syndrome (index participants), between Jan 23 and Oct 23, 2023. Clinic days were randomised (1:1) by computer-based randomisation to be an intervention (incentive) day or non-intervention (standard-of-care control) day. On intervention days, index participants were offered partner slips that entitled their partners to US$3 in compensation if they attended the same clinic for treatment. On control days, non-incentivised partner slips were offered. Participants were masked to the intervention before receipt of partner slips, while researchers including outcome assessors were unmasked. The primary outcome was the proportion of index participants, among those who took at least one partner slip, who had at least one partner attend the study clinic for treatment within 28 days of index diagnosis. This outcome was compared across the intervention and control groups by individual-level logistic regression, with robust standard errors to account for clustering, and analysed by intention to treat. Thematic analysis of two focus group discussions with pregnant women and 57 semi-structured interviews with pregnant women, partners, health-care staff, and intervention team members was also conducted. The parent IPSAZ study was registered on ClinicalTrials.gov (NCT05541081), and the current embedded trial was registered on the Pan African Clinical Trials Registry (PACTR202302702036850), both of which have been completed.

Findings: Between Jan 23 and Oct 23, 2023, 323 participants were diagnosed with a curable STI or treated for an STI syndrome. 156 (48%) of these index participants were randomly assigned to receive incentivised partner slips and 167 (52%) to receive standard-of-care control partner slips across 171 clusters (85 intervention clusters and 86 control clusters). Overall uptake of one or more partner slips by index participants was 91% (294 of 323 participants), with 87% uptake (136 of 156) in the intervention group and 95% uptake (158 of 167) in the control group. The median age of the 294 index participants who took partner slips was 24 years (IQR 21-29). No notable imbalances were observed in participant characteristics between the trial groups. Partners attended the clinic for treatment within 28 days of index diagnosis for 39 (29%) of 136 index participants who took at least one partner slip in the intervention group, and for 42 (27%) of 158 in the control group (odds ratio 1·11 [95% CI 0·66-1·86]; p=0·69). We identified potential barriers across the pathway from index diagnosis to partner treatment. Barriers to pregnant women informing partners included perceived risks of informing partners and complex relationship structures. Barriers to partner attendance were both structural, including time and costs, and cultural, including how men perceived clinics and their engagement with health care. Crucially, partners were not always aware of the availability of incentives.

Interpretation: Financial incentives did not address barriers to index participants informing partners, and ultimately did not improve partner attendance for STI treatment. Multifaceted packages addressing barriers for both the index individual and partner, and influencing multiple points in the partner notification and treatment pathway, are likely required to facilitate partner treatment.

Funding: Wellcome Trust.