Clinical Study Design Flashcards
Types of Treatment Studies
- Randomized Controlled Trial (RCT)
- Blind Trial
- Non-Blind Trial
- Adaptive Clinical 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)
RCT
A randomized controlled trial (or randomized control trial;[2] RCT) is a type of scientific (often medical) experiment which aims to reduce bias when testing a new treatment. The people participating in the trial are randomly allocated to either the group receiving the treatment under investigation or to a group receiving standard treatment (or placebo treatment) as the control. Randomization minimises selection bias and the different comparison groups allow the researchers to determine any effects of the treatment when compared with the no treatment (control) group, while other variables are kept constant. The RCT is often considered the gold standard for a clinical trial. RCTs are often used to test the efficacy or effectiveness of various types of medical intervention and may provide information about adverse effects, such as drug reactions. Random assignment of intervention is done after subjects have been assessed for eligibility and recruited, but before the intervention to be studied begins.
Random allocation in real trials is complex, but conceptually the process is like tossing a coin. After randomization, the two (or more) groups of subjects are followed in exactly the same way and the only differences between them is the care they receive. For example, in terms of procedures, tests, outpatient visits, and follow-up calls, should be those intrinsic to the treatments being compared. The most important advantage of proper randomization is that it minimizes allocation bias, balancing both known and unknown prognostic factors, in the assignment of treatments.[3]
Classifications of RCTs
By study design
- Parallel-group
- Crossover
- Cluster
- Factorial
By outcome of interest:(efficacy vs. effectiveness)
RCTs can be classified as “explanatory” or “pragmatic.”[35] Explanatory RCTs test efficacy in a research setting with highly selected participants and under highly controlled conditions.[35] In contrast, pragmatic RCTs (pRCTs) test effectiveness in everyday practice with relatively unselected participants and under flexible conditions; in this way, pragmatic RCTs can “inform decisions about practice.”[35]
By hypothesis:
(superiority vs. noninferiority vs. equivalence)
Another classification of RCTs categorizes them as “superiority trials”, “noninferiority trials”, and “equivalence trials”, which differ in methodology and reporting.
Types of Observational studies
- Descriptive
- Case report
- Case series
- Population study
- Analytical
- Cohort study
- -Prospective cohort
- -Retrospective cohort
- -Time series study
- Case-control study
- -Nested case-control study
- Cross-sectional study
- -Community survey (a type of cross-sectional study)
- Ecological study
Etiology
Etiology (/iːtiˈɒlədʒi/; alternatively aetiology or ætiology) is the study of causation, or origination. The word is derived from the Greek αἰτιολογία, aitiología, “giving a reason for” (αἰτία, aitía, “cause”; and -λογία, -logía).[1] More completely, etiology is the study of the causes, origins, or reasons behind the way that things are, or the way they function, or it can refer to the causes themselves.
Prospective cohort study
A prospective cohort study is a longitudinal cohort study that follows over time a group of similar individuals (cohorts) who differ with respect to certain factors under study, to determine how these factors affect rates of a certain outcome.[1] For example, one might follow a cohort of middle-aged truck drivers who vary in terms of smoking habits, to test the hypothesis that the 20-year incidence rate of lung cancer will be highest among heavy smokers, followed by moderate smokers, and then nonsmokers.
The prospective study is important for research on the etiology of diseases and disorders. The distinguishing feature of a prospective cohort study is that at the time that the investigators begin enrolling subjects and collecting baseline exposure information, none of the subjects have developed any of the outcomes of interest.
Retrospective cohort study
A retrospective cohort study, also called a historic cohort study, is a longitudinal cohort study used in medical and psychological research. A cohort of individuals that share a common exposure factor is compared to another group of equivalent individuals not exposed to that factor, to determine the factor’s influence on the incidence of a condition such as disease or death. Retrospective cohort studies have existed for approximately as long as prospective cohort studies.[1]
Observational Study Designs:
Case Control vs. Prospective Cohort vs. Retrospective Cohort
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