What question did this study set out to answer?

To model how receptive anal intercourse alters the measured effectiveness and statistical power of clinical trials evaluating topical vaginal microbicides against HIV transmission.

March 23, 2010Sexually Transmitted Diseases

Heterosexual Anal Intercourse Has the Potential to Cause a Significant Loss of Power in Vaginal Microbicide Effectiveness Studies

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To model how receptive anal intercourse alters the measured effectiveness and statistical power of clinical trials evaluating topical vaginal microbicides against HIV transmission.
Constructed a mathematical model incorporating microbicide efficacy, adherence probability during vaginal exposures, receptive anal intercourse frequency, and relative transmission probabilities.
Estimated the statistical power to detect a 40% effective microbicide in a simulated 160-endpoint trial across different rectal intercourse frequencies and a 20-fold higher transmission probability for rectal versus vaginal sex.
Assuming a 20-fold higher transmission risk per rectal act, statistical power to detect a 40% effective product in a 160-endpoint trial dropped from 90% to 56% when 1 in 50 sexual acts (2%) was rectal.
Increasing the frequency of receptive anal intercourse to 1 in 25 sexual acts (4%) further degraded study power to detect true microbicide effectiveness down to 34%.

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Implication

Modeling study reveals substantial loss of statistical power in microbicide trials from anal intercourse, highlighting the necessity of comprehensive behavioral counseling.

Cite This Study

McGowan et al. (2010) studied this question.

synapsesocial.com/papers/6a8574234f2eb4dbc91e5b45 https://doi.org/10.1097/olq.0b013e3181cd70c2

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Implication

Modeling study reveals substantial loss of statistical power in microbicide trials from anal intercourse, highlighting the necessity of comprehensive behavioral counseling.

Heterosexual Anal Intercourse Has the Potential to Cause a Significant Loss of Power in Vaginal Microbicide Effectiveness Studies

Key Points

Discussion

Implication

Cite This Study

Heterosexual Anal Intercourse Has the Potential to Cause a Significant Loss of Power in Vaginal Microbicide Effectiveness Studies

Key Points

Discussion

Implication

Cite This Study

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