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Knowledge of HIV Status Reduces Risk of Sexual HIV Transmission by 68%
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"Meta-Analysis of High-Risk Sexual Behavior in Persons Aware and Unaware They are Infected With HIV in the United States: Implications for HIV Prevention Programs"
JAIDS Journal of Acquired Immune Deficiency Syndromes: Volume 39(4) 1 August 2005 pp 446-453
Marks, Gary; Crepaz, Nicole PhD; Senterfitt, J Walton PhD; Janssen, Robert S MD
From the Division of HIV/AIDS Prevention, Centers for Disease Control and Prevention (CDC), Atlanta, GA.
Abstract
Objectives: To compare the prevalence of high-risk sexual behaviors in HIV+ persons aware of their serostatus with that in HIV+ persons unaware of their status in the United States and to discuss implications for HIV prevention programs.
Methods: A meta-analysis was conducted on 11 independent findings. Six findings compared HIV+ aware persons with independent groups of HIV+ unaware persons (between-group comparisons), and 5 findings compared seroconverting individuals before and after being notified of their HIV+ status (within-subject comparisons). Outcomes were self-reported unprotected anal or vaginal intercourse (UAV) during specified recall periods.
Results: The analysis integrating all 11 findings indicated that the prevalence of UAV with any partner was an average of 53% (95% confidence interval [CI]: 45%-60%) lower in HIV+ persons aware of their status relative to HIV+ persons unaware of their status. There was a 68% reduction (95% CI: 59%-76%) after adjusting the data of the primary studies to focus on UAV with partners who were not already HIV+. The reductions were larger in between-group comparisons than in within-subject comparisons. Findings for men and women were highly similar.
Conclusions: The prevalence of high-risk sexual behavior is reduced substantially after people become aware they are HIV+. Increased emphasis on HIV testing and counseling is needed to reduce exposure to HIV from persons unaware they are infected. Ongoing prevention services are needed for persons who know they are HIV+ and continue to engage in high-risk behavior.
Sexually transmitted HIV infection may stem from 2 groups of people: HIV+ persons unaware they are infected and HIV+ persons aware of their infection status. The Centers for Disease Control and Prevention (CDC) estimates that 850,000 to 900,000 persons are living with HIV in the United States and that approximately 650,000 are aware of their status and 250,000 are not.1,2 Little is known about the relative difference between these 2 groups in exposing uninfected sex partners to HIV. A better understanding of this relative difference can help to guide public health strategies and allocation of resources to fight the HIV/AIDS epidemic in the United States.
To reduce the risk of HIV transmission, the CDC recommends a variety of interventions in medical care and community settings for those who are aware of their status. Linkage to medical care and antiretroviral therapy, which may reduce viral load and transmission risk,3-6 and ongoing behavioral interventions are important approaches for those who know they are living with HIV. To reach those who are unaware of their infection, the CDC recommends making HIV counseling and testing more accessible and acceptable for people at high risk for HIV infection.7 Of course, both strategic pathways are important, and prevention efforts can be informed by even roughly estimating the differences in sexual risk behaviors between awareness groups. We performed a meta-analysis of findings that compared the prevalence of unprotected anal and vaginal intercourse (UAV) between persons who were aware and unaware of their HIV infection.
RESULTS
Eleven independent findings from 1988 through 2003 were included in the meta-analysis. Six were between-group comparisons, and 5 were within-subject comparisons. Table 1 presents the characteristics of the studies and the unadjusted findings. Every study showed that the prevalence of UAV was lower in the HIV+ aware group (or postnotification period) compared with the HIV+ unaware group (or prenotification period).
Two sets of results of the random-effects models are presented in Table 2: findings based on the unadjusted data and findings based on data adjusted to focus on at-risk sex partners. The combined ES for all 11 findings in the unadjusted model indicates that the prevalence of UAV was an average of 53% (95% CI: 45%-60%) lower in HIV+ aware persons relative to HIV+ unaware persons. The reduction was 68% (95% CI: 59%-76%) in the adjusted model (k = 11). Each of these reductions differed significantly from 0 (Z > 25, P < 0.001). In both models, the reduction was significantly larger in the between-group findings (k = 6) compared with the within-subject findings (k = 5) (unadjusted model: ƒÔ(1) 2 = 38.71, P < 0.0001; adjusted model: ƒÔ(1) 2 = 8.32, P < 0.01). The ESs of the men and women did not differ significantly in either model (unadjusted: ƒÔ(1) 2 = 0.18, P > 0.50; adjusted: ƒÔ(1) 2 = 2.47, P > 0.10).
Sensitivity Analyses
Sensitivity analyses indicated that no individual finding appreciably affected the overall (k = 11) or between-group (k = 6) ES in the two models. The ESs were affected less than ±3% (eg, absolute change from 68% to 70% reduction in the prevalence of UAV) with any single finding removed. For the unadjusted and adjusted models, the within-group ES (k = 5) changed no more than ±5% and the men's ES (k = 7) changed no more than ±4%. There was slightly more instability in the women's aggregated findings. The ES changed no more than ±4% in the women's unadjusted model but changed up to 8% in the adjusted model. For example, the ES was reduced nearly 8% in the adjusted model when the SHAS phase 1 finding was removed and was increased 4% in the adjusted model when the SHAS phase 2 finding was removed. These individual findings (especially the SHAS phase 1 finding) were heavily weighted in the aggregated analysis because of large sample sizes. In summary, the overall models (k = 11) showed a high level of stability. The stability decreased only slightly when analyses were performed separately for between-group and within-subject comparisons. The stability of the men's data exceeded the stability of the women's data in the adjusted model.
Finally, we examined the effect of using a weighted (as opposed to an unweighted) average of the adjustment studies that focused the analysis on at-risk sex partners. The meta-analytic findings were virtually identical when using these 2 methods (absolute difference of 1% in the estimated ESs).
DISCUSSION
Our meta-analysis shows that the prevalence of high-risk sexual behavior is markedly lower in HIV+ persons aware of their seropositive status than in HIV+ persons unaware of their status. The findings of studies conducted in the United States from 1988 through 2003 were highly consistent despite methodologic differences among the investigations. A highly similar picture emerges from studies that examined STD acquisition rates between HIV-infected aware and unaware persons.27-30 These studies were not included in the meta-analysis because of the qualitatively different nature of the outcome variable and the fact that the partner serostatus adjustment could not validly be applied to those studies. Of persons presenting at an STD clinic in New Orleans (1989-1991) with a first-time diagnosis of gonorrhea, new gonorrhea diagnoses were 50% lower during 2 to 3 years of follow-up in persons aware relative to unaware that they were HIV+.27 In an STD clinic in Miami in 1988 through 1989, the percentage with a newly diagnosed STD declined 11% in the 6 months after they learned they had HIV infection compared with the 6 months before their HIV+ diagnosis.28 STD studies conducted in other countries show even stronger findings. Of HIV+ persons presenting at a genitourinary clinic in London in 1994, the prevalence of diagnosed STDs was 73% lower in the year after HIV diagnosis than in the year before.29 Finally, of HIV+ women presenting at prenatal and pediatric clinics in Rwanda (1988-1989), the prevalence of clinically diagnosed gonorrhea was 54% lower in the year after than the year before HIV diagnosis.30
In our analysis, the between-group and within-subject comparisons demonstrated significant reductions in self-reported UAV, although the reduction was higher in the between-group design. One explanation is that a group of HIV+ aware persons may differ from a group of HIV+ unaware persons on other variables associated with unsafe sex, potentially accentuating the difference between the groups. For example, on average, people who are unaware they are infected with HIV are likely to be younger than people who are aware they are HIV+.31 The prevalence of unsafe sex has been found to be higher among younger than older MSM. 31,32
Another issue concerns whether behavior change in HIV+ aware persons is maintained over time. Additional analysis of the SHAS phase 2 data set showed that the prevalence of UAV in the most recent encounter with an at-risk partner was remarkably similar among subgroups of HIV+ aware men who differed in length of time they knew they were HIV+ (range: 1-24 months [17%], 25-48 months [16%], 49-72 months [17%], 73-96 months [14%], and >96 months [13%]). The prevalence was 39% in HIV+ unaware men. A highly similar pattern was seen in HIV+ aware women in SHAS phase 2 and in men and women in SHAS phase 1. One other study not included in the meta-analysis because it assessed sexual behavior of HIV+ aware persons but not HIV+ unaware persons did not confirm this pattern. The prevalence of UAV was higher in persons aware of their infection for 5 or more years compared with those diagnosed more recently.33 These mixed results make it difficult to reach conclusions at this time about the stability of behavior change after being diagnosed HIV+. This issue merits attention in future research.
Our meta-analytic findings must be viewed within the context of the methodologic limitations of the primary studies. First, the studies used self-reported sexual behavior. Self-reports are open to socially desirable responding, and some HIV+ aware persons may underreport unprotected sex with at-risk partners.34 US studies of HIV serodiscordant homosexual35 and heterosexual36 couples demonstrate high levels of agreement (approximately 90%) between couple members in self-reports of condom use, however. We were not able to gauge the level of partner agreement in the studies analyzed here. Second, we were not able to examine the number of sex partners placed at risk by HIV+ aware and HIV+ unaware persons, because those data were not available in the literature. The difference between these groups in the prevalence of UAV may not necessarily reflect the magnitude of difference in the number of sex partners placed at risk. Our analysis, however, provides a starting point for a more refined model when additional data become available. Third, the difference in the prevalence of UAV between HIV+ aware and HIV+ unaware persons may not reflect differences in HIV transmission rates between groups. Actual transmission depends on a host of biologic factors. For example, transmission risk is increased when an individual who is the source of exposure is in the primary HIV infection stage,37 has a high viral load,3,4 or has an STD.38,39 These factors would elevate transmission risk more from HIV+ unaware than HIV+ aware persons, because unaware persons as a group are more likely to be in the primary infection stage, to a have higher viral load because they are not in medical care, and to have an STD.27-30
Our findings reinforce the need for a multidimensional approach to HIV prevention.7 Resources and efforts are needed to make HIV testing opportunities more accessible (eg, rapid tests) and to reduce barriers to testing so that infected persons learn their status. Public health campaigns targeting young MSM, especially young MSM of color, are urgently needed, because many of these men are unaware they are infected.40 Promising but underused methods for reaching such persons include offering HIV testing routinely in all health care settings in high HIV prevalence areas7; offering testing at venues that attract high-risk persons; adding HIV testing capacity to all effective educational outreach and risk reduction interventions41; and gaining the cooperation of current HIV+ aware persons to reach members of their sexual and social networks for HIV testing, counseling, and care if needed.42
Clearly, HIV counseling and testing alone are not enough to control the HIV epidemic. Behavioral interventions for people aware they are infected and for those at high risk for HIV are needed. Those interventions may reduce sexual risk behavior by as much as 30% to 40%.43-45 For those aware that they are HIV+, the challenge is to find settings and approaches for delivering prevention programs to this population over time. The HIV clinic is an ideal setting for offering prevention messages and counseling to HIV+ persons and for integrating prevention with routine medical care.46 Such counseling from HIV providers has been shown to be efficacious in reducing unprotected intercourse in HIV+ patients.44 Other promising interventions have been delivered by HIV+ peers in community settings.47 Assisting HIV+ people to establish social networks that encourage risk reduction and provide social support for seeking medical care and adhering to treatment regimens has also shown promise in demonstration projects.48 Together, these approaches may contribute to more rapid control of the HIV epidemic in the United States and elsewhere.
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