Interventional Studies

Overview

• Interventional studies are prospective studies designed to evaluate the direct impact of therapies or preventative measures by assigning subjects to intervention groups
• 2 types of interventional studies
  • clinical trials
    • individuals assigned to competing intervention groups
  • community interventions
    • assigment at the group level (e.g., one community receives fluoridinated water and one does not)
• Highest quality if
  • randomized 
  • controlled
  • double-blinded

Clinical Drug Trials

• 4 phases for clinical trials evaluating new drugs
  • phase I 
    • small number of healthy subjects (<100)
    • purpose
      • safety and dosage
  • phase II 
    • small number of diseased patients (100-300)
    • purpose
      • efficacy and side effects
  • phase III
    • large number of diseased patients (>1,000)
    • purpose
      • effectiveness and monitoring of adverse reactions
    • compare to standard of care
  • phase IV 
    • post-marketing surveillance
    • purpose
• detects rare or long-term adverse effects

Factorial Design

• Randomizes patients into different interventions with 2 or more variables being studied in each intervention 
  • allows researchers to study the effects of multiple independent variables independently and mutually on a dependent variable
• e.g., group 1 studies effect of treatments A+B on variable X, group 2 studies effects of A alone, group 3 studies effect of B alone, and group 4 is the control group receiving no treatment

Crossover Design

• Participants alternate receiving intervention and placebo
• Participants act as own controls 
  • improves power and precision of study
  • need washout period between interventions
  • all patients receive intervention