Session Details

FD2: Causal Inference and Causal Diagrams in Medical Decision Making Using Big Real World Observatio
(Event: SMDM 40th Annual Meeting: Montreal, QC, Canada)

Oct 14, 2018 9:00AM - Oct 14, 2018 5:30PM
Session Type: Short Course- Full Day

Description
Background
One of the most important tasks of decision makers is to derive causal interpretations using both statistical analyses of original datasets and decision analysis. Often an intervention, action or risk factor is modeled to have a "causal effect" on one or more model parameters (e.g., probability, rate, or mean of outcome). Therefore, both the biostatistician and the decision analyst need tools to check: (1) when effect estimates have a causal interpretation and when they do not; and (2) the appropriate methods to derive causal effects instead of merely statistical associations.
Course Type
Full Day
Course Level
Intermediate
Format Requirements
The course will consist of lectures, exercises drawn from the published literature, hands-on software practicals in R, and interactive discussion. The intended audience includes researchers from all substance matter fields, statisticians, epidemiologists, and decision analysts interested either in methods of causal analysis or causal interpretation of results based on the underlying method. Requirements: Basic knowledge in epidemiologic methods (confounding). Basic understanding of writing code and a laptop with installed R software. R code for software practicals will be provided, and instructions for installing R will be sent to attendees before the conference.
Overview
This course combines theory/methods with practical programming exercises using the open-source software R. This course will provide an introduction to the principles of causation and causal diagrams, with focus on Directed Acyclic Graphs (DAG) and a brief introduction to methods for causal inference including multivariate analysis, propensity scores, g-formula, marginal structural models with inverse probability of treatment weighting, and structural nested models with g-estimation (lecture - exercises - discussion). We will use the “target trial” concept and a counterfactual approach with “replicates” to apply causal methods and valid per-protocol analysis of sustained treatment regimens to big real world observational data and pragmatic trials with postrandomization confounding. The objectives of this course are to draw and interpret causal diagrams, to decide which biostatistical/epidemiological methods must be used in different situations to derive causal effect parameters, to understand causal modeling, and to be able to apply these methods in large real world data and pragmatic trials with hands-on practice in R. Published cardiovascular, oncology, HIV, nutrition and obstetrics examples will be used to: *** Adjust for non-adherence in randomized clinical trials, where both the intention-to-treat and the naïve per protocol analyses can fail to yield the true causal intervention effect; *** Assess the “fallibility of estimating direct effects” (i.e., adjusting for intermediate steps); *** Adjust for time-independent confounders (i.e., confounder affects both risk factor and disease), where standard stratification, regression analysis or propensity score methods yield valid causal effects if all confounders are measured, and *** Adjust for time-dependent confounding (i.e., the confounder simultaneously acts as an intermediate step in the causal chain between risk factor and disease), where standard regression analysis fails and causal methods such as marginal structural models or g-estimation must be used.
Description & Objectives
Course Objectives:
  1. to define causal interventions and actions, draw and interpret causal diagrams, and apply the rules of causal diagrams to distinguish causal from non-causal statistical associations.
  2. to decide which biostatistical/epidemiological methods must be used in different situations to derive causal effect parameters.
  3. to use causal diagrams to estimate the direction of bias in "non-causal" models.
  4. to understand the conceptual approaches of causal modeling
  5. to know how these methods are applied in big real world data and pragmatic trials 

Published cardiovascular, oncology, HIV, nutrition and obstetrics examples will be used to:

  • Adjust for non-adherence in randomized clinical trials, where both intention-to-treat and naïve per protocol analyses may fail to yield the true causal intervention effect
  • Assess the “fallibility of estimating direct effects” (i.e., adjusting for intermediate steps);
  • Adjust for time-independent confounders (i.e., confounder affects both risk factor and disease), where standard stratification, regression analysis, propensity score methods and matching/balancing approaches yield valid causal effects if all confounders are measured
  • Adjust for time-dependent confounding (i.e., the confounder simultaneously acts as intermediate step in the causal chain between risk factor and disease), where standard regression analysis fails and "causal methods" such as marginal structural models or g-estimation must be used. 

Software Practicals: 
We will work through three practical analyses using the software R to demonstrate adjustment for baseline and time-dependent confounding in a randomized trial of cholesterol-lowering medications and mortality.

  • Example 1: Drawing a causal diagram for a pragmatic trial in patients with elevated cholesterol levels with potential non-adherence; discussing the potential for bias.
  • Example 2: Adjusting for baseline confounders to improve efficiency and interpretability of the intention-to-treat effect using standardization.
  • Example 3: Focusing on the placebo arm only, demonstrating how to control for bias introduced by non-adherence using baseline and time-dependent confounding with marginal structural models.
Course Directors
  • Uwe Siebert
    • UMIT, Dept. of Public Health, Health Services Research & Health Technology Assessment / Harvard Univ., Dept. Health Policy & Management, Institute for Technology Assessment / ONCOTYROL, Division for HTA
  • Douglas E Faries
    • Eli Lilly and Co
  • Felicitas Kuehne
    • Department of Public Health, Health Services Research and Health Technology Assessment, UMIT - University for Health Sciences, Medical Informatics and Technology
Course Faculty
  • Ellen Caniglia
    • Dept. of Epidemiology, Harvard Chan School of Public Health / Dept. of Population Health, New York University School of Medicine
  • Eleanor Murray
    • Dept. of Epidemiology, Harvard Chan School of Public Health
  • Lucia Petito
    • Dept. of Epidemiology, Harvard Chan School of Public Health

  

 

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