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Clinical Trial

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Clinical Trial, Research Study, Randomized Control Trial, Randomized Clinical Trial, Published Randomized Control Trial, Cohort study, Case-control study, Cross Sectional Study, Qualitative Study, Qualitative Research, Observational Study, Intention to Treat Analysis, Propensity Score, Run-in Period

  • See Also
  1. Statistical Terms
  2. Research GRADE
  • Types
  • Randomized Study
  1. Randomized Clinical Trial
    1. In randomized trials, participants are assigned by chance to different groups
    2. Researchers and participants are typically "blinded" to the assigned group
  2. Randomized Controlled Trial (RCT)
    1. In randomized controlled trials, a control group is compared to one or more treatment groups
    2. As with other randomized trials, researchers and participants are typically "blinded" to group assignment
    3. Randomized Controlled Trials, when performed well, are the most reliable level of Research Study
  • Types
  • Observational Studies
  1. Observational Study
    1. Individuals are observed or specific outcomes are measured
    2. No intervention is performed to attempt to alter the outcome of those studied
  2. Cohort study
    1. Cross-section or population is selected (e.g. nurses)
    2. Group selection is based on specific characteristics that researchers intend to study (e.g. nurses who smoke versus non-smokers)
    3. Study participants are followed, evaluating specific outcome measures at specific time points (e.g. cancer at 5, 10, 15 and 20 years)
    4. Cohort studies may be retrospective (e.g. historical database reviews) or prospective
    5. Risk of confounding factors that distort results
  3. Case-control study
    1. Two groups of participants are studied: One group with a disease, and the other without
      1. The 2 groups are otherwise similar (age, gender, socioeconomic factors)
    2. Each group is interviewed with medical medical review and other analysis
      1. Researchers identify factors that distinguish the 2 groups and may identify causative factors for those with the disease
  4. Cross Sectional Study
    1. A specific, random cohort of participants (e.g. 20 year old men) are studied (interviewed, surveyed) at single point in time
  5. Qualitative Study
    1. Research focuses on nonnumeric data to investigate individual or group characteristics
    2. Describes experience and behaviors, Perceptions and beliefs with language
  • Types
  • Additional Statistical Analysis Tools
  1. Intention to Treat Analysis (ITT)
    1. Statistical analysis of study participants based on the original, randomized treatment group assignment
    2. Includes patients regardless of the treatment they ultimately received (or did not receive)
    3. ITT reduces the study bias that comes from excluding patients who are not fully compliant with study protocol
  2. Propensity Score matching
    1. Used by observational studies to simulate a Randomized Control Trial
    2. Randomization is simulated by applying statistical techniques to divide a large study cohort into groups
    3. Goal is for groups to be similar in all identified characteristics OTHER than those factors being studied
    4. Propensity Score is the probability of group assignment based on baseline characteristics
  3. Run-in Period
    1. Study technique in which all participants are given a Placebo after study inclusion but BEFORE randomization
      1. Identifies participants most suitable as study participants
      2. Intended to exclude certain participants (e.g. Placebo responders, noncompliance)
    2. Run-in Periods are intended to increase a study's power, more likely to detect a statistical difference
    3. Used more commonly in industry sponsored studies
    4. Risk of decreased external validity, and risks participant unblinding
      1. Laursen (2019) Clin Epidemiol 11:169-84 +PMID: 30809104 [PubMed]
  • Resources
  1. What types of Studies are there? (InformedHealth.org)
    1. https://www.ncbi.nlm.nih.gov/books/NBK390304/