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Equal behaviors, unequal risks:
The role of partner transmission potential in racial HIV disparities among men who have sex with men (MSM) in the United States
Eli Rosenberg
Department of EpidemiologyEmory University Rollins School of Public HealthAtlanta, GA
July 23, 2012
Colleen Kelley, Brandon O'Hara, Paula Frew, John Peterson, Travis Sanchez, Carlos del Rio, Patrick Sullivan
Emory University Center for AIDS
Research
Washington D.C., USA, 22-27 July 2012www.aids2012.org
• HIV prevalence among MSM is high and MSM continue to bear the burden of HIV incidence in the US
• Black MSM, particularly young black MSM, continue to be overrepresented among new infections
• Reasons for racial disparity remain unclear
• Unknown degree to which prevalence of HIV without viral suppression perpetuates incidence disparities
• Theoretically, greater likelihood of encountering a partner who might transmit HIV translates into increased incidence
HIV and MSM
Washington D.C., USA, 22-27 July 2012www.aids2012.org
Measures of transmission risk for disparities research• How do we measure an individual’s risk of having unprotected
sex in a community?
• Suggests a measure that incorporates the spectrum of HIV infection, diagnosis, linkage to care, treatment, suppression
• Our toolkit of measures is limited for this tasko HIV prevalenceo Community viral loado Population viral load
• Need for a broad and relevant public health measure
Washington D.C., USA, 22-27 July 2012www.aids2012.org
• Proportion of individuals in whole population with a current VL sufficient to transmit HIV
A new measure: Transmission Potential Prevalence (TPP)
¿ h𝑤𝑖𝑡 𝑉𝐿≥400𝑃𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛
• Crosses prevalence with VL measures
• VL cut-point unknown for MSM. Used conservative estimate of 400 copies/ml.
Washington D.C., USA, 22-27 July 2012www.aids2012.org
What are the TPPs in the black and white MSM communities of Atlanta and how do
they relate to HIV risk?
Washington D.C., USA, 22-27 July 2012www.aids2012.org
Study Design
Eligibility: > 18-39 years old, non-Hispanic black or white, had male sex in last 3 months, not in mutually monogamous relationship, reside in metro Atlanta
Recruitment: venue-time-space sampling
Baseline visit:o HIV testing: Rapid test, WB confirmatory, viral loadso Partnership-level behavioral questionnaire
709 men (399 B, 310 W) enrolled from 7/2010 - 6/2012
Prospective HIV/STI incidence cohort study of black and white MSM in Atlanta
Washington D.C., USA, 22-27 July 2012www.aids2012.org
Demographics and outcomes
Black MSM
(n = 399)
White MSM
(n = 310)p
Age, median 25 y 28 y < .0001Education > HS 74 % 89 % < .0001
Male partners, prev. 12 mo., median 5 7.5 < .0001
HIV Prevalence 42 % 14 % < .0001HIV Incidence, per 100 PY 6.4 1.0 0.006
More details:O’Hara et al TU PE-133
Washington D.C., USA, 22-27 July 2012www.aids2012.org
Results: Viral load measures
More details:Kelley et al MO PE-264
Mean log10(VL) p VL > 400
copies/ml p
A. Community VL Black 2.5 0.74 48 % 0.93White 1.9 47 %
B. Population VL
Black 3.5 0.77 61 % 0.66White 4.1 57 % C. Transmission Potential
Black n/a 25 % < .0001White 8 %
Washington D.C., USA, 22-27 July 2012www.aids2012.org
• Translate TPP and partner selection patterns into probabilities that HIV-negative, black and white MSM might encounter a potentially transmitting partner
• Race-specific, deterministic modelso TPP represents partner poolo UAI racial mixing patterns
3 groups: black, white, other Racial exclusivity 70% Among non-exclusive men, mixing with 3 groups
o Monte Carlo simulation to estimate variability (x 100,000)
Behavioral model
Washington D.C., USA, 22-27 July 2012www.aids2012.org
Results: Behavioral modelProbability of having ≥ 1 partner with HIV transmission potential
39%
18%
3 7
10 25
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• Despite similar CVL and PVL, sizeable racial differences in TPP and associated exposure risk
• Model results suggest limited ability of behavioral interventions alone to eliminate disparities
• Communities with high TPP should be focus of new resources to prevent transmission
• HIV surveillance systems can be adapted to include TPP to understand transmission risk in subgroups and make meaningful comparisons
Conclusions
Washington D.C., USA, 22-27 July 2012www.aids2012.org
• Current VL does not reflect durable virologic suppression
• Model does not account for other determinants of transmission
• UAI serosorting not included
• Does not explain what originally gave rise to disparities
Limitations
Washington D.C., USA, 22-27 July 2012www.aids2012.org
Our data support targeting resources to dramatically reduce
TPP among black MSM by increasing testing, linkage, and
retention in HIV care in order to reduce disparities in HIV
incidence, supported by coordinated behavioral interventions to
increase effectiveness of treatment.
Relevance
Washington D.C., USA, 22-27 July 2012www.aids2012.org
Thank you !!
• R01-MH085600• R01-HD067111• KL2-RR025009
• P30 AI050409 (Emory CFAR)
Supported by NIH #:
InvestigatorsRecruitersEvent staffRetention specialistsData team
Our participants! Eli [email protected]