Sharpening Bounds on Principal Effects with Covariates

Details

• Alternative Title:
  Biometrics
• Personal Author:
  Long, Dustin M. ; Hudgens, Michael G.
• Description:
  Estimation of treatment effects in randomized studies is often hampered by possible selection bias induced by conditioning on or adjusting for a variable measured post-randomization. One approach to obviate such selection bias is to consider inference about treatment effects within principal strata, that is, principal effects. A challenge with this approach is that without strong assumptions principal effects are not identifiable from the observable data. In settings where such assumptions are dubious, identifiable large sample bounds may be the preferred target of inference. In practice these bounds may be wide and not particularly informative. In this work we consider whether bounds on principal effects can be improved by adjusting for a categorical baseline covariate. Adjusted bounds are considered which are shown to never be wider than the unadjusted bounds. Necessary and sufficient conditions are given for which the adjusted bounds will be sharper (i.e., narrower) than the unadjusted bounds. The methods are illustrated using data from a recent, large study of interventions to prevent mother-to-child transmission of HIV through breastfeeding. Using a baseline covariate indicating low birth weight, the estimated adjusted bounds for the principal effect of interest are 63% narrower than the estimated unadjusted bounds.
• Subjects:
  Article Bounds Breast Feeding Causal Effects Data Interpretation, Statistical Female HIV Infections Humans Infant Infant, Newborn Infectious Disease Transmission, Vertical Malawi Partial Identifiability Potential Outcomes Prevalence Principal Strata Randomized Controlled Trials As Topic Risk Assessment

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• Source:
  Biometrics. 69(4):812-819.
• Pubmed ID:
  24245800
• Pubmed Central ID:
  PMC4086842
• Document Type:
  Journal Article
• Funding:
  P30 AI050410/AI/NIAID NIH HHS/United States ; R01 AI085073/AI/NIAID NIH HHS/United States ; R01-AI085073/AI/NIAID NIH HHS/United States ; R37 AI054165/AI/NIAID NIH HHS/United States ; U48-DP001944/DP/NCCDPHP CDC HHS/United States ; U54 GM104942/GM/NIGMS NIH HHS/United States ; U54-GM104942/GM/NIGMS NIH HHS/United States
• Volume:
  69
• Issue:
  4
• Collection(s):
  CDC Public Access
• Main Document Checksum:
  urn:sha256:bf95bb6844bb66fa91884e9981a7c052a82d53c93c7aec6d051298fb2baf992a
• Download URL:
  https://stacks.cdc.gov/view/cdc/30027/cdc_30027_DS1.pdf
• File Type:
  [PDF - 510.63 KB ]