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''Circumstantial Determinants'': An Efficient Approach to Reaching People in Need of HIV Prevention?

This study proposes and validates a "Circumstantial Determinants" approach in Zimbabwe, demonstrating that targeting HIV prevention services based on specific social circumstances and settings rather than self-reported risk behaviors can significantly improve the reach and efficiency of identifying priority populations for intervention.

Original authors: Bagnay, S. H., Gregson, S., Skovdal, M., Maswera, R., Moorhouse, L. R., Ncube, G., Tsenesa, B., Mandizvidza, P., Pickles, M., Garnett, G. P., Mugurungi, O., Nyamukapa, C.

Published 2026-06-22

📖 5 min read🧠 Deep dive

CC BY 4.0

Original authors: Bagnay, S. H., Gregson, S., Skovdal, M., Maswera, R., Moorhouse, L. R., Ncube, G., Tsenesa, B., Mandizvidza, P., Pickles, M., Garnett, G. P., Mugurungi, O., Nyamukapa, C.

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ⚕️ This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer

The Big Problem: Missing the People Who Need Help Most

Imagine you are trying to hand out free umbrellas to people during a sudden rainstorm. Currently, most programs only give umbrellas to people who:

Walk into a shop and ask for one (self-referral).
Are already standing under a shelter (routine health visits).

The problem is that the people getting most wet—the ones running through the storm without a coat—are often healthy, don't realize they are in danger, or are too embarrassed to admit they are running through the rain. They never walk into the shop, so they never get an umbrella.

This paper asks: How do we find these people without having to interview everyone in the city?

The New Idea: "Circumstantial Determinants" (The Weather Map)

Instead of asking people, "Are you running in the rain?" (which they might lie about or not realize), the researchers suggest looking at where they are and what is happening around them.

They call these factors "Circumstantial Determinants" (CDs). Think of these as "Weather Signs."

If you see someone standing at a busy bus stop, they are likely to get wet.
If you see someone at a crowded bar, they are likely to get wet.
If you see someone looking very sad or stressed, they might be more likely to get wet.

The paper argues that instead of screening every single person for risky behavior, we should set up our umbrella stations at these specific "Weather Signs."

How They Tested It

The researchers went to Zimbabwe and surveyed over 9,000 people. They first identified who was "at risk" (the "Priority Population") based on actual risky behaviors (like having multiple partners). Then, they looked at the "Weather Signs" (CDs) for these people.

They found that certain signs were very good at predicting who needed an umbrella:

For Men: Living on a farm estate, having no religion, having negative social connections, visiting bars often, having poor mental health, or holding traditional "macho" views.
For Women: Living on a farm estate, having no religion, visiting bars, experiencing violence from a partner, or having poor mental health.

The Results: How Well Did the "Weather Map" Work?

1. The "Bar" Strategy
If you set up an umbrella stand at every bar and beer hall:

You would catch 48.5% of the men who actually need umbrellas (the priority population).
You would also give umbrellas to 25.1% of men who aren't really at risk (lower-risk men).
Analogy: It's like setting up a stand at a popular party. You get a lot of the people you want, but you also give some freebies to people who weren't planning to get wet.

2. The "Combo" Strategy
The researchers found that combining signs works even better.

If you target men at bars PLUS men with poor mental health PLUS men with no religion, you can reach 77.1% of the high-risk men.
The "cost" is that you also reach more low-risk men (53.7%), but you are still catching a much higher percentage of the people who actually need help compared to just looking at bars alone.

3. The "Mental Health" Strategy for Women
For women, targeting those with poor mental health was a huge win. It reached 32% of high-risk women. If you combined this with other signs (like living on a farm estate or experiencing violence), you could reach 54.1% of the women who need help.

The "Umbrella Chain" (The Cascade)

Finding the people is only step one. The next step is making sure they actually use the umbrella. The researchers looked at the "chain" of events:

Do they want an umbrella? (Motivation)
Can they get one? (Access)
Do they know how to use it? (Skill)

They found that the "broken links" in this chain were different for different groups:

Men at bars: They usually wanted umbrellas and knew how to use them, but sometimes couldn't get one.
Men with poor mental health: They wanted umbrellas, but getting one was much harder for them.
Women on farms: They had access, but sometimes didn't know how to use them effectively.
Women with poor mental health: They had access, but often lacked the confidence or skills to use them.

The Lesson: You can't use the same sales pitch for everyone. If you are at a bar, you might just need to hand out the umbrella. If you are helping someone with poor mental health, you might need to teach them how to use it and help them get it.

The Bottom Line

This paper is a "proof of concept." It shows that looking at a person's circumstances (where they live, their mental state, their social circle) is a smart, efficient way to find the people most at risk of HIV.

It suggests that instead of trying to interview everyone to find the "risky" ones, health programs should go to the places and talk to the groups where these "Weather Signs" are most common. This approach could catch many more people who are currently slipping through the cracks of the system.

Important Note: The paper emphasizes that this is a new idea being tested. It is not yet a final rule for doctors to follow, but it shows a very promising new way to think about stopping the spread of HIV.

Technical Summary: "Circumstantial Determinants": An Efficient Approach to Reaching People in Need of HIV Prevention?

Problem Statement

Current HIV prevention and testing programs primarily rely on self-referral or attendance at routine health services. This approach often fails to reach high-risk individuals who are healthy, underestimate their infection risk, or under-report sexual risk behaviors due to social desirability bias. Existing targeting strategies, such as risk scores based on biological and behavioral variables, have demonstrated poor performance. Furthermore, routine screening often relies on self-reports that may not predict future risk, and standalone testing centers or self-testing kits are limited by low risk perception. The authors argue that biological and behavioral risks are embedded within socio-cultural and economic environments, suggesting that targeting the "circumstances" creating these risks may be a more effective strategy than targeting individual characteristics alone.

Methodology

This study utilized data from the seventh round of the Manicaland General Population Open-Cohort survey conducted in Zimbabwe between July 2018 and December 2019 ( $N=9,141$ ). The study population included HIV-negative individuals aged 15–54.

Definitions:

Priority Population: HIV-negative, sexually active individuals reporting one or more specific sexual risk behaviors (SRBs) associated with HIV acquisition (e.g., multiple partners, concurrent partnerships, transactional sex, non-regular partners, or age-disparate relationships for women).
Circumstantial Determinants (CDs): Defined as "spatial settings, social interactions, life situations or events, socio-cultural norms, and individual predispositions" that increase exposure to HIV risks. Ten potential CDs were investigated, including residence on agricultural estates, lack of religious affiliation, negative social capital, regular visits to bars/beerhalls, intimate partner violence (IPV), poor mental health, and adherence to traditional masculine norms.

Analytic Steps:

Identification of CDs: Multiple logistic regression was used to calculate age-adjusted odds ratios (AORs) for each CD category. CDs with $AOR \ge 1.30$ and $p \le 0.01$ were selected as significant predictors of being in the priority population.
Efficiency Assessment: The study calculated the reach (percentage of the priority population captured) and efficiency (Risk Ratio of reaching priority vs. general population) for individual CDs and their combinations using "AND/OR" (targeting one or both) and "AND" (targeting the overlap) approaches.
Algorithm Development: Receiver Operating Characteristic (ROC) curve algorithms were developed to predict priority population membership based on CD exposure. Four algorithms were tested: two optimizing the Area Under the Curve (AUC) and two optimizing sensitivity, using stepwise selection on training (75%) and test (25%) datasets.
Cascade Analysis: HIV prevention condom cascades (HPCs) were constructed for subgroups defined by specific CDs to identify barriers (motivation, access, effective use) in condom use with non-regular partners.

Key Results

Identification of Determinants:
Six CDs were significantly associated with the priority population for both men and women ( $AOR \ge 1.30, p \le 0.01$ ):

Residence on agricultural estate compounds.
No religious affiliation.
Negative social capital.
Regular visits to bars or beerhalls.
Poor mental health.
Holding traditional masculine social norms ("sex drive" dimension).
Note: For women, exposure to intimate partner violence (IPV) was also a significant determinant.

Reach and Efficiency:

Men: Targeting men who regularly visit bars/beerhalls alone reached 48.5% of the priority population but also targeted 25.1% of the lower-risk general population. Combining this with other CDs (e.g., poor mental health, negative social capital, no religious affiliation) increased reach to 77.1% of the priority population, though this also increased the targeting of lower-risk men to 53.7%.
Women: Targeting women with poor mental health reached 32.0% of the priority population. Expanding to include women on agricultural estates, those with IPV, those visiting bars, and those with no religious affiliation increased reach to 54.1% of the priority population.
Risk Ratios: Combinations of CDs generally yielded higher Risk Ratios (RR) than single CDs, indicating more efficient targeting. For example, targeting men with negative social capital and bar visits yielded an RR of 1.52.

Algorithm Performance:

The ROC algorithms demonstrated modest discriminatory ability. For men, the AUC peaked at 0.63; for women, it remained below 0.60.
Sensitivity increased stepwise as more CDs were added (reaching ~95.5% for men in the final step), but this came at the cost of declining specificity (dropping to ~15.9% for men).
The study noted that gains in sensitivity became smaller than losses in specificity after step 4 for men and step 2 for women in the training datasets.

Condom Cascades:

Significant differences in barriers were observed between CD-defined subgroups.
Men: Those with poor mental health were less likely to report access to condoms compared to bar-goers ($OR: 0.37$).
Women: Women with poor mental health were more likely to report effective condom use than those on agricultural estates ($OR: 1.94$). However, women with poor mental health faced higher odds of low HIV knowledge (a barrier to motivation) and lacked practical skills/partner barriers compared to women on agricultural estates.

Significance and Claims

The authors present this work as a proof-of-concept demonstrating the potential utility of the Circumstantial Determinants (CD) approach for HIV prevention.

Targeting Efficiency: The study claims that incorporating CDs into program design can significantly expand the reach of HIV services to the priority population while remaining more efficient than untargeted universal delivery.
Differentiated Interventions: The findings suggest that different CDs create distinct barriers within the prevention cascade. Therefore, interventions can be tailored; for example, addressing access barriers for men with poor mental health versus addressing knowledge and skill barriers for women with poor mental health.
Practical Application: The authors argue that while some CDs (like residence on estates) are easy to target physically, others (like mental health or IPV) require nuanced, non-stigmatizing strategies, potentially through collaborations with community health programs (e.g., the Friendship Bench).
Limitations: The authors modestly acknowledge that the cross-sectional nature of the data limits causal inference, that the specific strength of associations may vary by location and time, and that the algorithms showed only modest discriminatory power. They emphasize that further research is needed to generalize these findings and refine the approach for specific local contexts.

The paper concludes that the CD approach offers a viable framework to strengthen HIV prevention services by identifying individuals currently overlooked by mainstream strategies, provided that the cost of reaching these specific circumstantial groups does not exceed the savings achieved by targeting a smaller, higher-risk population.