The 130th Annual Meeting of APHA

Abstract #44734

Steven D. Pinkerton, PhD, Center for AIDS Intervention Research, Medical College of Wisconsin, 2071 N Summit Ave, Milwaukee, WI 53202, 4144567700, Pinkrton@mcw.edu, Harrell W. Chesson, PhD, Division of STD Prevention, Centers for Disease Control, 1600 Clifton Road, MS E44, Atlanta, GA 30333, Peter Layde, MD, MSc, Wisconsin Injury Research Center, Medical College of Wisconsin, 9200 W. Wisconsin Ave, Milwaukee, WI 53226, and . and the NIMH Multisite HIV Prevention Trial Group, Center for AIDS Intervention Research, Medical Collge of Wisconsin, 2071 N Summit Ave, Milwaukee, WI 53202.

Background: Most STD/HIV sexual risk reduction intervention trials are evaluated using behavioral outcomes as their main indicators of intervention effectiveness. But, how good are behavioral measures as surrogate markers for STD infection? In particular, do the behavioral changes that are commonly assessed in risk reduction interventions accurately reflect changes in STD risk?

Methods: We applied a mathematical model of HIV/STD transmission to empirical data from a large HIV prevention intervention to estimate pre- to post-intervention changes in intervention participants’ STD risk. Then we used the coefficient of determination to assess the strength of association between changes in STD risk and changes in three behavioral measures: proportion of acts of intercourse for which condoms were used, number of sex partners, and number of acts of unprotected intercourse.

Results: The number of acts of unprotected intercourse appears to be a superior marker for less infectious STDs, such as HIV, whereas the number of partners may be preferable for highly infectious STDs, such as gonorrhea. Changes in the proportion of acts of intercourse for which condoms were used was not strongly correlated with changes in STD risk under most of the conditions examined in this analysis.

Conclusion: The utility of different measures of sexual behavior change as markers for changes in STD risk––hence, expected incidence––depends on the infectivity and prevalence of the target STD.

Learning Objectives:

At the conclusion of the session, participants will
• understand how and why changes in sexual behaviors often are used in STD/HIV prevention trials as surrogates for changes in STD/HIV incidence
• appreciate how the utility of a particular behavior, when used as a surrogate for incidence, depends on the epidemiological characteristics of the particular STD
• understand how simple mathematical models can be used to explicate the relationship between sexual behaviors and STD risk

Presenting author's disclosure statement:
I do not have any significant financial interest/arrangement or affiliation with any organization/institution whose products or services are being discussed in this session.