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Why are some trials not randomized?

Why are some trials not randomized?. Inexperienced researchers May be impractical or unethical Design flaws may invalidate the conclusions. Questions addressed by RCT. Is drug A better than drug B or placebo for treatment of a particular condition

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Why are some trials not randomized?

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  1. Why are some trials not randomized? • Inexperienced researchers • May be impractical or unethical • Design flaws may invalidate the conclusions

  2. Questions addressed by RCT • Is drug A better than drug B or placebo for treatment of a particular condition • Is written or verbal advice better to help patients make decisions about treatment options

  3. RCT: advantages • Allows rigorous evaluation of a single variable in a defined patient group • Prospective • Designed to test the null hypothesis • Reduces bias • Allows for meta-analysis

  4. RCT: disadvantages • Expensive and time consuming!! • Often not enough patients • Often patients not followed for long enough • Most funding comes from government or industry • Surrogate endpoints often used • Failure to randomize all eligible patients

  5. Cohort studies • 2 or more groups selected based on differences in exposure to a particular agent (medication, environmental toxin, etc.) • Groups are followed to see who develops disease • Cohort studies can be used to define risk factors

  6. Case-control studies • Patients with a particular disease or condition are identified (“case”) and matched with controls (different disease, general population, relatives) • Data are collected about the two groups (medical records, interview) and compared

  7. Case control studies and cohort studies usually address what may cause a disease (etiology) rather than how to treat a disease • Can the case-control design show causality? • Case-control studies are retrospective

  8. Examples of case control studies • Sleeping position and sudden infant death syndrome • Brain tumors and cell phone use

  9. Cross sectional surveys • Interview a representative sample of subjects • Collect data at time point of interview with or without reference retrospectively to events in the past • Examples?

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