Measuring concurrent partnerships: potential for underestimation in UNAIDS recommended method

Recently formed age-disparate partnerships are associated with elevated HIV-incidence among young women in South Africa

OBJECTIVE

Cross-sectional and cohort studies draw different conclusions on whether age-disparate partnerships increase HIV-acquisition risk for young women. We investigated whether age-disparities were associated with HIV-infection risk early in relationships. This could result in the exclusion of women who seroconverted during high-risk age-disparate partnerships from cohort studies of HIV incidence - which exclude HIV-positive women - and explain null findings in these studies.

DESIGN

Prospective cohort study.

METHODS

We used data on 15-24-year-old, HIV-negative women in heterosexual partnerships (N = 830) in KwaZulu-Natal, South Africa. The association between age-disparate partnering (i.e., male partner ≥5 years older) and subsequent HIV seroconversion was assessed using Cox hazard models. We examined heterogeneity in HIV-acquisition risk by duration of partnership (defined by quartiles) at cohort enrolment.

RESULTS

During 1139 person-years (mean: 1.4 years) of follow-up, 54 (6.5%) women seroconverted, a weighted HIV-incidence estimate of 4.41/100 person-years [95% confidence interval (CI): 3.30-6.06]. HIV-acquisition risk did not differ significantly between women in age-disparate vs. age-similar partnerships (adjusted hazard ratios: 1.10, 95% CI: 0.55-2.21). However, for women in the shortest partnership quartile (<1.09 years) at baseline, risk of HIV seroconversion was higher for women in age-disparate partnerships (adjusted hazard ratios: 3.13, 95% CI: 1.02-9.65, P = 0.047). HIV acquisition was not statistically different by partnership type among women in longer partnerships.

CONCLUSION

The association between age-disparate partnerships and HIV-acquisition risk is evident early in young women's relationships. Results provide a potential explanation for null findings in cohort studies, whose research designs may exclude women in such partnerships, and affirms the elevated risk of HIV acquisition for young women in age-disparate relationships.

Coital frequency and condom use in age-disparate partnerships involving women aged 15 to 24: evidence from a cross-sectional study in KwaZulu-Natal, South Africa

OBJECTIVE

This study examines the role of age-disparate partnerships on young women's HIV risk by investigating coital frequency and condom use within age-disparate partnerships involving women aged 15 to 24.

DESIGN

A community-based, cross-sectional study was conducted.

SETTING

Participants were randomly selected using a two-stage random sampling method in uMgungundlovu district, KwaZulu-Natal, South Africa, between June 2014 and June 2015.

PARTICIPANTS

A total of 1306 15-24-year-old women in an ongoing heterosexual partnership were included in the analysis. Participants had to be a resident in the area for 12 months, and able to provide informed consent and speak one of the local languages (Zulu or English).

PRIMARY AND SECONDARY OUTCOME MEASURES

Sexual frequency was assessed by asking participants how many times they had sex with each partner in the past 12 months. The degree of condomless sex within partnerships was assessed in the survey by asking participants how often they used a condom with their partners.

RESULTS

Age-disparate partnerships were associated with a higher order category (once, 2-5, 6-10, 11-20, >20) of coital frequency (adjusted OR (aOR) 1.32, p<0.05, 95% CI 1.02 to 1.71) and with sex on more than 10 occasions (aOR 1.48, p<0.01, 95% CI 1.12 to 1.96) compared with age-similar partnerships. Age-disparate partnerships were also more likely to involve sex on more than 10 occasions with inconsistent condom use (aOR 1.43, p<0.05, 95% CI 1.04 to 1.96) in the previous 12 months.

CONCLUSION

The finding that increased sexual activity is positively associated with age-disparate partnerships adds to the evidence that age-disparate partnerships pose greater HIV risk for young women. Our study results indicate that interventions to reduce risky sexual behaviour within age-disparate partnerships remain relevant to reducing the high HIV incidence rates among adolescent girls and young women.

Age-disparate partnerships and HSV-2 among adolescent girls and young women in South Africa: implications for HIV infection risk

OBJECTIVE

There is an urgent need to understand high HIV-infection rates among young women in sub-Saharan Africa. While age-disparate partnerships have been characterised with high-risk sexual behaviours, the mechanisms through which these partnerships may increase HIV-risk are not fully understood. This study assessed the association between age-disparate partnerships and herpes simplex virus type-2 (HSV-2) infection, a factor known to increase HIV-infection risk.

METHODS

Cross-sectional face-to-face questionnaire data, and laboratory HSV-2 and HIV antibody data were collected among a representative sample in the 2014/2015 household survey of the HIV Incidence Provincial Surveillance System in KwaZulu-Natal, South Africa. Among 15-24-year-old women who reported having ever had sex (n=1550), the association between age-disparate partnerships (ie, male partner ≥5 years older) and HSV-2 antibody status was assessed using multivariable Poisson regression models with robust variance. Analyses were repeated among HIV-negative women.

RESULTS

HSV-2 prevalence was 55% among 15-24-year-old women. Women who reported an age-disparate partnership with their most recent partner were more likely to test HSV-2 positive compared with women with age-similar partners (64% vs 51%; adjusted prevalence ratio (aPR):1.19 (95% CI 1.07 to 1.32, p<0.01)). HSV-2 prevalence was also significantly higher among HIV-negative women who reported age-disparate partnerships (51% vs 40 %; aPR:1.25 (95% CI 1.05 to 1.50, p=0.014)).

CONCLUSIONS

Results indicate that age-disparate partnerships are associated with a greater risk of HSV-2 among young women. These findings point towards an additional mechanism through which age-disparate partnerships could increase HIV-infection risk. Importantly, by increasing the HSV-2 risk, age-disparate partnerships have the potential to increase the HIV-infection risk within subsequent partnerships, regardless of the partner age-difference in those relationships.

HIV Risk Among Adolescent Girls and Young Women in Age-Disparate Partnerships: Evidence From KwaZulu-Natal, South Africa

BACKGROUND

Evidence on the role of age-disparate partnerships in high HIV-infection rates among young women in sub-Saharan Africa remains inconclusive. This study examined the HIV-infection risk associated with age-disparate partnerships among 15- to 24-year-old women in a hyperendemic setting in South Africa.

METHODS

Face-to-face questionnaire, and laboratory HIV and viral load data were collected during 2014-2015 among a representative sample (15-49 years old) in KwaZulu-Natal. The association between age-disparate partnerships (age difference ≥5 years) and HIV status among 15- to 24-year-old women (N = 1459) was assessed using multiple logistic regression analyses. Data from the male sample on all on-going partnerships (N = 1229) involving 15- to 24-year-old women were used to assess whether young women's age-disparate male partners were more likely to have a viral load ≥1000 copies per milliliter, a marker of HIV-infection risk.

RESULTS

Women reporting an age disparity in any of their 3 most recent partnerships were more likely to test HIV positive compared to women with only age-similar partners [adjusted odds ratio (aOR): 1.58, 95% confidence interval (CI): 1.20 to 2.09, P < 0.01]. Among partnerships men reported with 15- to 24-year-old women, the age-disparate male partners were more likely to be HIV positive and have a viral load ≥1000 copies per milliliter (aOR: 2.05, 95% CI: 1.30 to 3.24, P < 0.01) compared with age-similar partners. Results were similar for each category of age disparity: partners 5-9 years older (aOR: 2.01, 95% CI: 1.18 to 3.43, P = 0.010) and those ≥10 years older (aOR: 2.17, 95% CI: 1.01-4.66, P = 0.048).

CONCLUSIONS

Results indicate that age-disparate partnerships increase young women's HIV risk, although conclusive evidence was not ascertained. Interventions addressing risk from age-disparate sexual partnering, including expanding antiretroviral treatment among older partners, may help to reduce HIV incidence among young women.

Concurrency and other sexual partnership patterns reported in a survey of young people in rural Northern Tanzania

African adolescents and young adults remain at substantial risk of infection with HIV and other sexually transmitted infections (STIs), and AIDS is the leading cause of death among African adolescents (10–19 years). Sexual partnership patterns influence transmission risk of sexually transmitted infections. We describe patterns reported by youth (15-30y) in a community-based survey in Tanzania. Among participants reporting multiple partners, we investigated factors associated with reported concurrency. Female (N = 6513) and male (N = 7301) participants had median ages of 21 and 22 years, respectively. Most participants (92%) reported having previously been sexually active, of whom 15% of males and <1% of females reported ≥4 partners in the past year. The point prevalence of concurrency was 2.3% (95%CI 1.9–2.9) for females and 10.6% (95%CI 9.3–12.1) for males. High levels of multiple and concurrent partnerships were reported by those previously married. Females were more likely than males to report having spousal/regular partners and longer partnership lengths. Compared to males, the partnerships reported by females were less likely to be new partnerships, and more likely to be defined by the respondent as still ‘ongoing’. Females reporting younger sexual debut were more likely to report concurrent sexual partners. Far fewer young women reported multiple and concurrent partnerships, but we cannot definitively conclude that concurrency was uncommon for women, because stigma towards women’s multiple sexual partnerships might contribute to substantial under-reporting, as was found in extensive qualitative research in the study population. This study provides one of the most comprehensive quantitative descriptions of partnership patterns of young people in an African setting. Interventions addressing sexual risk among youth should involve male partners, empower women to protect themselves within different types of partnerships, and encourage a greater openness about young people’s sexual relationships.

HIV Prevalence and ART Use Among Men in Partnerships with 15-29 Year Old Women in South Africa: HIV Risk Implications for Young Women in Age-Disparate Partnerships

This study assesses whether men's ART use mitigates HIV-risk within age-disparate partnerships. Using data from the 2012 South African National HIV survey, we analyzed differences in HIV prevalence and ART use between men in age-disparate and age-similar partnerships with young women aged 15-29 using multiple logistic regression analyses. Within partnerships involving women 15-24 years old, men in age-disparate partnerships were more likely to be HIV-positive (5-9 year age-gap: aOR 2.8, 95%CI 1.4-5.2; p < 0.01; 10+ year age-gap: aOR 2.2, 95%CI 1.0-4.6; p < 0.05). Men in age-disparate partnerships who were 5-9 years older were significantly more likely to be HIV-positive and ART-naïve (aOR 2.4, 95%CI 1.2-4.8; p < 0.05), while this was not the case for men 10+ years older (aOR 1.5, 95%CI 0.7-3.6; p = 0.32). No evidence was found that 25-29 year old women were at greater HIV-risk in age-disparate partnerships. Our results indicate that young women aged 15-24 have a greater likelihood of exposure to HIV through age-disparate partnerships, but ART use among men 10+ years older could mitigate risk.

Why Are Orphaned Adolescents More Likely to Be HIV Positive? Distinguishing Between Maternal and Sexual HIV Transmission Using 17 Nationally Representative Data Sets in Africa

PURPOSE

Why do orphans have higher rates of HIV infection than nonorphaned peers? Research consistently assumes that orphans acquire HIV primarily through sexual behavior, but infections may instead be due to maternal transmission. Although these two pathways have very different implications for HIV programs and policies, their relative contribution has not been previously examined. In this research, we compare the contribution of maternal and sexual transmission to HIV infection among orphans in Africa.

METHODS

We use Demographic and Health Survey data for 21,463 women and 18,359 men from 17 countries. We propose a conceptual framework linking orphanhood to HIV, and use mediation analysis and structural equation modeling to compare the potential contribution of maternal transmission (measured through direct pathways from orphanhood to HIV) and sexual transmission (measured through reports of risky sexual behavior) to orphan HIV infection.

RESULTS

Our results suggest that maternal transmission is the predominant pathway of HIV infection among orphaned adolescents: there is strong evidence for a direct pathway from maternal (odds ratio [OR]: 2.45; 95% confidence interval [CI]: 1.72-3.51 for females and OR: 2.45; 95% CI: 1.53-3.90 for males) and double orphanhood (OR: 2.69; 95% CI: 1.97-3.66 and OR: 2.53; 95% CI: 1.68-3.82, respectively) to HIV; greater excess HIV risk in maternal versus paternal orphans. The contribution of sexual behavior is largely not significant. We do not observe correspondingly high orphan disparities in other sexually transmitted diseases.

CONCLUSIONS

Maternal transmission is a more likely explanation than sexual transmission for heightened HIV infection among orphans. These results suggest that programs designed to address HIV infection among adolescents should focus on reducing maternal transmission and on identifying and testing undiagnosed HIV among orphans.

Sexual Behaviour of Men and Women within Age-Disparate Partnerships in South Africa: Implications for Young Women's HIV Risk

Background

Age-disparate partnerships are hypothesized to increase HIV-risk for young women. However, the evidence base remains mixed. Most studies have focused only on unprotected sex among women in the partnership. Consequently, little is known about other risky behaviours, such as transactional sex, alcohol use, and concurrency, as well as the behaviours of the men who partner with young women. We therefore examined differences in various sexual behaviours of both young women and their male partners by partnership age difference.

Methods

We used nationally representative data from South Africa (2012) on partnerships reported by 16–24 year old black African women (n = 818) and by black African men in partnerships with 16–24 year old women (n = 985). We compared sexual behaviours in age-disparate partnerships and age-similar partnerships, using multiple logistic regression to control for potential confounders and to assess rural/urban differences.

Results

Young women in age-disparate partnerships were more likely to report unprotected sex than young women in similar-aged partnerships (aOR:1.51; p = 0.014; 95%CI:1.09–2.11). Men in partnerships with young women were more likely to report unprotected sex (aOR:1.92; p<0.01; 95%CI:1.31–2.81), transactional sex (aOR:2.73; p<0.01; 95%CI:1.64–4.56), drinking alcohol before sex (aOR:1.60; p = 0.062; 95%CI:0.98–2.61), and concurrency (aOR:1.39; p = 0.097; 95%CI:0.94–2.07) when their partners were five or more years younger. The association between age-disparate partnerships and transactional sex (aOR:4.14; p<0.01; 95%CI: 2.03–8.46) and alcohol use (aOR:2.24; p<0.013; 95%CI:1.20–4.19) was only found in urban areas.

Conclusions

Results provide evidence that young women’s age-disparate partnerships involve greater sexual risk, particularly through the risky behaviours of their male partners, with the risk amplified for young women in urban areas.

The Cape Town boyfriend and the Joburg boyfriend: women's sexual partnerships and social networks in Khayelitsha, Cape Town

In South Africa, young people's "multiple" or "concurrent" partnerships have been increasingly prominent in public health discourses - as drivers of HIV transmission. Multiple partnerships are typically framed in moralising, negative terms and depicted primarily as male-driven, within a broader framework of women's vulnerability and use of sex for survival and material gain. Based on ethnographic fieldwork with adolescents and young adults in Khayelitsha township near Cape Town, this article investigates young women's partnerships by exploring their complex interpersonal and social dynamics. We unpack women's multiple motivations for, and careful management strategies of, both sexual and social relationships in a broader context of socioeconomic exclusion, threats to health and wellbeing, social obligations and relationships of care. The meanings and practices associated with young people's relationships are more than the sum of individual sexual behaviours, rigid cultural scripts or simply a locus of "risk." The data presented here highlight some of the limitations of "prevention" approaches that do not take into account this nuanced and multilayered view of such relationships. The affective and empathetic dimensions of young peoples' relationships, as well as the socioeconomic contexts in which they occur should also be considered. Without accounting for this context, standard "prevention" approaches are less likely to succeed.

Partner age differences and concurrency in South Africa: Implications for HIV-infection risk among young women

Partner-age difference is an HIV-risk factor among young women in Africa, but the underlying mechanisms are poorly understood. We used nationally representative data among black South Africans (men: 3,530; women: 3,946) to examine the proportion of women in partnerships involving male partner concurrency by age of female partners and by age-disparate (≥5 years) partnerships. Of all partners reported by men, 35 % of young (16-24) women were in partnerships involving male partner concurrency of 4 weeks or longer during the past 12 months. Young women in age-disparate partnerships were more likely to be in partnerships with men who had other concurrent partners (9 %; OR 1.88 p < 0.01) and more likely to be connected to an older sexual network. Our results suggest that the relationship between male concurrency and age-disparate relationships may increase HIV risk for young women by connecting them to larger and older sexual networks.

A new approach to measuring partnership concurrency and its association with HIV risk in couples

Empirical estimates of the association between concurrent partnerships (CP) and HIV risk are affected by non-sampling errors in survey data on CPs, e.g., because respondents misreport the extent of their CPs. We propose a new approach to measuring CPs in couples, which permits assessing how respondent errors affect estimates of the association between CPs and HIV risk. Each couple member is asked (1) to report whether s/he has engaged in CPs and (2) to assess whether his/her partner has engaged in CPs, since their couple started. Cross-tabulating these data yields multiple classifications (with varying combinations of sensitivity/specificity) of the CPs of each couple member. We then measure the association between CPs and HIV outcomes according to each classification. The resulting range of estimates is an indicator of the uncertainty associated with respondent errors. We tested this approach using data on 520 matched couples drawn from the Likoma Network Study. Results suggest that existing tests of the concurrency hypothesis are affected by significant uncertainty.

Assessment of a new web-based sexual concurrency measurement tool for men who have sex with men

BACKGROUND

Men who have sex with men (MSM) are the most affected risk group in the United States' human immunodeficiency virus (HIV) epidemic. Sexual concurrency, the overlapping of partnerships in time, accelerates HIV transmission in populations and has been documented at high levels among MSM. However, concurrency is challenging to measure empirically and variations in assessment techniques used (primarily the date overlap and direct question approaches) and the outcomes derived from them have led to heterogeneity and questionable validity of estimates among MSM and other populations.

OBJECTIVE

The aim was to evaluate a novel Web-based and interactive partnership-timing module designed for measuring concurrency among MSM, and to compare outcomes measured by the partnership-timing module to those of typical approaches in an online study of MSM.

METHODS

In an online study of MSM aged ≥18 years, we assessed concurrency by using the direct question method and by gathering the dates of first and last sex, with enhanced programming logic, for each reported partner in the previous 6 months. From these methods, we computed multiple concurrency cumulative prevalence outcomes: direct question, day resolution / date overlap, and month resolution / date overlap including both 1-month ties and excluding ties. We additionally computed variants of the UNAIDS point prevalence outcome. The partnership-timing module was also administered. It uses an interactive month resolution calendar to improve recall and follow-up questions to resolve temporal ambiguities, combines elements of the direct question and date overlap approaches. The agreement between the partnership-timing module and other concurrency outcomes was assessed with percent agreement, kappa statistic (κ), and matched odds ratios at the individual, dyad, and triad levels of analysis.

RESULTS

Among 2737 MSM who completed the partnership section of the partnership-timing module, 41.07% (1124/2737) of individuals had concurrent partners in the previous 6 months. The partnership-timing module had the highest degree of agreement with the direct question. Agreement was lower with date overlap outcomes (agreement range 79%-81%, κ range .55-.59) and lowest with the UNAIDS outcome at 5 months before interview (65% agreement, κ=.14, 95% CI .12-.16). All agreements declined after excluding individuals with 1 sex partner (always classified as not engaging in concurrency), although the highest agreement was still observed with the direct question technique (81% agreement, κ=.59, 95% CI .55-.63). Similar patterns in agreement were observed with dyad- and triad-level outcomes.

CONCLUSIONS

The partnership-timing module showed strong concurrency detection ability and agreement with previous measures. These levels of agreement were greater than others have reported among previous measures. The partnership-timing module may be well suited to quantifying concurrency among MSM at multiple levels of analysis.

Measuring prevalence and correlates of concurrent sexual partnerships among young sexually active men in Kisumu, Kenya

Our objectives were to: (1) compare multiple measures of partnership concurrency, including the UNAIDS-recommended definition and (2) describe the prevalence and correlates of concurrent sexual partnerships among young Kenyan men. We analyzed 10,907 lifetime partnerships of 1,368 men ages 18-24 years enrolled in a randomized trial of male circumcision to reduce HIV-1 incidence in Kisumu. Partnership concurrency was determined by overlapping dates and examined over varying recall periods and assumptions. The lifetime prevalence of concurrency was 77 %. Sixty-one percent of all partnerships were concurrent and factors associated with concurrency differed by partner type. Point prevalence of concurrency at the time of the interview was consistently the highest and UNAIDS-recommended definition was the most conservative (25 vs. 18 % at baseline, respectively). Estimates of concurrency were influenced by methods for definition and measurement. Regardless of definition, concurrent partnerships are frequent in this population of young, sexually active men in high HIV prevalence Kisumu, Kenya.

Patterns and predictors of multiple sexual partnerships among newly arrived Latino migrant men

Multiple sexual partnerships (MSP), both concurrent and serial short gap, are thought to increase the risk of HIV and sexually transmitted infection (STI) acquisition and transmission. In this study we evaluate potential individual and environmental risk factors for engaging in MSP in a cohort of newly arrived Latino migrant men (LMM) in New Orleans, LA, USA. Participants were surveyed at three time points over a nine-month period to examine factors associated with MSP. Of the 113 men, 32.5 % reported ever MSP. In 290 observations, 19.5 % of men had concurrent, and 15.0 % had serial short gap partnerships in at least one interviews. Substance was associated with MSP, OR (95 % CI) 2.00 (1.16, 3.45) whereas belonging to a community organization was found to be protective, OR 0.32 (0.17, 0.59). Interventions to reduce substance use and promote social connection are needed to prevent a potential HIV/STI epidemic in this population.

Descriptive and injunctive norms related to concurrent sexual partnerships in Malawi: implications for HIV prevention research and programming

Concurrent sexual partnerships are hypothesized to be a contributing factor to Malawi's HIV epidemic. As social norms influence health behavior and have been found to influence sexual behavior, the purpose of this study was to explore two types of norms, descriptive and injunctive norms, toward concurrent sexual partnerships in Malawi. Data from 40 focus group discussions and 20 in-depth interviews conducted in five districts in Malawi, which included 318 participants aged 18-55 years, were analyzed. Participants perceived that concurrent sexual partnerships were extremely common, and believed that very few individuals in their communities were not in concurrent sexual partnerships. However, participants perceived that others in their communities heavily disapproved of concurrent sexual partnerships outside of polygamy, as polygamy was viewed as an acceptable type of partnership because it was conducted in the open. Participants asserted that there were no traditional practices that promoted concurrent sexual partnerships, and perceived that those that engaged in the behavior were for the most part stigmatized by community members. Further research is needed to obtain a thorough understanding of the way in which the perceived actions and beliefs of peers influence the beliefs, feelings and actions of individuals to strengthen HIV programming efforts in the region.

Measuring and modelling concurrency

This article explores three critical topics discussed in the recent debate over concurrency (overlapping sexual partnerships): measurement of the prevalence of concurrency, mathematical modelling of concurrency and HIV epidemic dynamics, and measuring the correlation between HIV and concurrency. The focus of the article is the concurrency hypothesis - the proposition that presumed high prevalence of concurrency explains sub-Saharan Africa's exceptionally high HIV prevalence. Recent surveys using improved questionnaire design show reported concurrency ranging from 0.8% to 7.6% in the region. Even after adjusting for plausible levels of reporting errors, appropriately parameterized sexual network models of HIV epidemics do not generate sustainable epidemic trajectories (avoid epidemic extinction) at levels of concurrency found in recent surveys in sub-Saharan Africa. Efforts to support the concurrency hypothesis with a statistical correlation between HIV incidence and concurrency prevalence are not yet successful. Two decades of efforts to find evidence in support of the concurrency hypothesis have failed to build a convincing case.

The effect of interview method on self-reported sexual behavior and perceptions of community norms in Botswana

Since self-reports of sensitive behaviors play an important role in HIV/AIDS research, the accuracy of these measures has often been examined. In this paper we (1) examine the effect of three survey interview methods on self-reported sexual behavior and perceptions of community sexual norms in Botswana, and (2) introduce an interview method to research on self-reported sexual behavior in sub-Saharan Africa. Comparing across these three survey methods (face-to-face, ballot box, and randomized response), we find that ballot box and randomized response surveys both provide higher reports of sensitive behaviors; the results for randomized response are particularly strong. Within these overall patterns, however, there is variation by question type; additionally the effect of interview method differs by sex. We also examine interviewer effects to gain insight into the effectiveness of these interview methods, and our results suggest that caution be used when interpreting the differences between survey methods.

Unpacking the recommended indicator for concurrent sexual partnerships

Using sexual behaviour survey data, we examine the methodological choice for the time period underlying the UNAIDS Reference Group on Estimates, Modelling, and Projections recommended 'point prevalence' indicator for concurrency. The results confirm that 6 months before the interview is a good time point for calculating the recommended indicator, but this retrospective estimate is substantially lower than the estimate of concurrency based on the number of current partnerships. The discrepancy is only partially explained by disproportionate missing data in those with more sexual partners.

Measuring concurrency: an empirical study of different methods in a large population-based survey and evaluation of the UNAIDS guidelines

BACKGROUND

Recent UNAIDS guidelines recommend measuring concurrency 6 months before the interview date, based on overlapping partnership dates. This has theoretical advantages, but little is known about how well it can be measured in practice.

METHODS

The assumptions underlying the UNAIDS measure were tested using data from a sexual behaviour survey conducted in rural northern Malawi. All resident adults aged 15-59 were eligible. Questions included self-reported concurrency and dates for all marital and nonmarital partnerships in the past 12 months.

RESULTS

A total of 6796 women and 5253 men were interviewed, 83 and 72% of those eligible, respectively. Since few women reported multiple partners, detailed analysis was restricted to men. Overall 19.2% [95% confidence interval (CI) 18.1-20.2] of men self-reported concurrent relationships in the past year (almost all of those with more than one partner). Using overlapping dates the estimate was 16.7% (15.7-17.7). Excluding partnerships which tied on dates (making overlap uncertain) or restricting the analysis to the three most recent partners gave similar results. The UNAIDS 6-month measure was 12.0% (11.1-12.9), and current concurrency was 11.5% (10.6-12.4). The difference between dates-based and self-reported 12-month measures was much larger for unmarried men: 11.1% (9.7-12.4) self-reported; 7.1% (6.9-8.2) on dates. Polygyny (15% of married men) and the longer duration of relationships stabilized the estimates for married men. Nonmarital partnerships were under-reported, particularly those starting longer ago.

CONCLUSIONS

The difficulties of recall of dates for relationships, and under-reporting of partners lead to underestimation of concurrency using date-based measures. Self-reported concurrency is much easier to measure and appears more complete.

Exploring the relative costs of contact tracing for increasing HIV case finding in sub-Saharan countries

BACKGROUND

Contact tracing (CT) has rarely been used to improve HIV case finding in sub-Saharan Africa because of concerns regarding privacy protection and possibly high costs.

METHODS

We estimate the relative cost of identifying an undiagnosed HIV infection through CT compared with client-initiated voluntary counseling and testing (VCT) and door-to-door provider-initiated testing (PIT). We used data from the Likoma Network Study, a study of sexual networks and HIV infection conducted on the small island of Likoma in northern Malawi, to inform these calculations.

RESULTS

In Likoma, the probability that partners of HIV index cases could be traced and that they would consent to HIV testing and counseling was high and varied by partner type. HIV prevalence ranged from 48.1% to 66.7% among the partners who were tested. Per newly diagnosed infection, CT is rarely a cheaper case finding approach than VCT in populations with HIV prevalence > 5%. In populations with HIV prevalence < 5%, CT is an attractive case-finding approach relative to VCT when few HIV-infected individuals are aware of their status. Compared with door-to-door PIT, CT is almost always preferred when the population prevalence is below 10%, unless CT costs are prohibitively high. When HIV prevalence is >10%, providing CT for current spouses of index cases remains an attractive approach to HIV case finding.

CONCLUSIONS

CT could complement client-initiated VCT or door-to-door PIT in a large number of sub-Saharan populations affected by generalized epidemics of varying magnitudes.