Clinical study design


Clinical study design

Clinical study design is the formulation of trials and experiments in medical and epidemiological research, sometimes known as clinical trials. Many of the considerations here are shared under the more general topic of design of experiments but there can be others, in particular related to patient confidentiality and ethics.

Contents

Outline of types of designs for clinical studies

Treatment studies

  • Randomized controlled trial
    • Double-blind randomized trial
    • Single-blind randomized trial
    • Non-blind trial
  • Nonrandomized trial (quasi-experiment)
    • Interrupted time series design (measures on a sample or a series of samples from the same population are obtained several times before and after a manipulated event or a naturally occurring event) - considered a type of quasi-experiment

Observational studies

Important considerations

When choosing a study design, many factors must be taken into account. Different types of studies are subject to different types of bias. For example, recall bias is likely to occur in cross-sectional or case-control studies where subjects are asked to recall exposure to risk factors. Subjects with the relevant condition (e.g. breast cancer) may be more likely to recall the relevant exposures that they had undergone (e.g. hormone replacement therapy) than subjects who don't have the condition.

The ecological fallacy may occur when conclusions about individuals are drawn from analyses conducted on grouped data. The nature of this type of analysis tends to overestimate the degree of association between variables.

Seasonal studies

Conducting studies in seasonal indications (such as allergies, Seasonal Affective Disorder, influenza, and others) can complicate a trial as patients must be enrolled quickly. Additionally, seasonal variations and weather patterns can effect a seasonal study.[1][2]

Other terms

  • The term retrospective study is sometimes used as another term for a case-control study. This use of the term "retrospective study" is misleading, however, and should be avoided because other research designs besides case-control studies are also retrospective in orientation.
  • Superiority trials are designed to demonstrate that one treatment is more effective than another.
  • Non-inferiority trials are designed to demonstrate that a treatment is at least not appreciably worse than another.
  • Equivalence trials are designed to demonstrate that one treatment is as effective as another.
  • When using "parallel groups", each patient receives one treatment; in a "crossover study", each patient receives several treatments.
  • A longitudinal study research subjects over two or more points in time; by contrast, while a cross-sectional study assesses research subjects at one point in time.

See also

External links

References


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