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Sample size calculation for active-arm trial with counterfactual incidence based on recency assay
Fei Gao1, David V Glidden2, James P Hughes3
1Fred Hutchinson Cancer Research Center, Seattle, USA.
Statistical Communications in Infectious Diseases
|July 26, 2022
Summary
New methods can estimate HIV incidence in trials for pre-exposure prophylaxis (PrEP) without a placebo group. This approach uses HIV recency assays, enabling efficient trials for new HIV prevention strategies.
Area of Science:
- Biomedical science
- Epidemiology
- Public health
Background:
- Significant advancements in pre-exposure prophylaxis (PrEP) for HIV prevention have been made.
- New PrEP medications and delivery methods are under development to expand options.
- Future non-inferiority trials face feasibility challenges due to high efficacy of current PrEP.
Purpose of the Study:
- To develop a feasible method for evaluating new PrEP efficacy.
- To construct a counterfactual estimate of HIV incidence for control groups.
- To enable efficient clinical trials for novel HIV prevention strategies.
Main Methods:
- Proposing a cohort study augmenting HIV screening with laboratory markers for recent infections.
- Developing assumptions for estimating counterfactual HIV incidence.
- Conducting sample size and power calculations for trial comparisons.
Main Results:
- The proposed method allows for reasonable sample sizes and desirable statistical power in simulations.
- Hypothetical trials for men who have sex with men (MSM), transgender women (TGW), and young women in sub-Saharan Africa were considered.
- Calculated sample sizes were found to be feasible.
Conclusions:
- One-arm trials utilizing counterfactual placebo incidence derived from recency assays are feasible.
- These trials can be conducted with reasonable screening sample sizes.
- Adequate statistical power can be achieved to determine treatment efficacy for new PrEP agents.
Keywords:
HIV preventioncounterfactual placebo incidencepre-exposure prophylaxisrecency assaysample size calculationMore Related Videos
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