Retrospective vs Prospective Study

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 Retrospective vs. Prospective Study
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What is a Retrospective Study?
Retrospective, the term comprises two words i.e.
retro which means in the past and spective
which means to look. Thus, a retrospective
analyzes the events of information that had
already occurred in the past. In a retrospective
study, the outcome of the reference studies has
already occurred before a retrospective study is
initiated. The researcher or an author of a
retrospective study can collect the data from the
registry. In a retrospective study, after the
collection of data, the research question is
framed.
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What are the Advantages of Retrospective Study?

• Less time consuming and cheaper Retrospective
  studies are cheaper and require less time for
  completion. As the data related to the study is
  already available and the researcher compiles and
  compares the data between and subjects and
  control, retrospective studies provide immediate
  results.
• Effective in rare disease Retrospective study is
  quiet effective in rare diseases. Data related to
  the rare disease is available from various
  centres to arrive at an evaluable study
  population.

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• Initial screening Sometimes the retrospective
  studies are done as an initial screening for
  prospective studies.
• No-follow-up Retrospective studies uses the data
  already available in the literature or the
  registry. Thus, there is no risk of loss of
  follow-up in retrospective studies.
• Large data-set Retrospective makes use of large
  data-set. This may provide more accurate results.

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What are the Types of Retrospective Studies?

• Retrospective cohort studies This study is also
  known as the historic cohort study.
• Case series and case reports Case reports are a
  type of retrospective study in which the
  researcher reports symptoms or instructive case
  that was not previously seen with a medical
  condition.
• Case-Control Studies Case-control studies are
  better than case series and case reports.

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What is a Prospective Study?
Prospective studies are done in the present to
analyze the outcome in the future. In the
prospective study, the information is required to
be generated and is not available before the
start of the study. An example of a prospective
study is to follow-up with a group of alcohol
drinkers to identify whether drinking alcohol for
10-years is linked to liver disease. It is to be
noted that none of the subjects enrolled under
the study should have the outcome of interest.
For instance, in the above example, none of the
subjects should have liver disease before the
start of the study.
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What are the Advantages of Prospective Study?

• New disease risk factors Prospective studies are
  important in analyzing the risk factors for new
  diseases for which the data is not available.
  This will help in the effective management of the
  disease.
• Accurate results Because of well-controlled
  study design and accurate generation of data, the
  results provided by prospective studies are
  relatively more authentic.

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• Detailed data analysis Detailed analysis of the
  outcome and other statistical factors can be done
  in prospective studies. Exposure can be measured
  before the outcome and the incidence and disease
  process can also be determined.
• Multiple outcomes Multiple outcomes can also be
  obtained from prospective studies.
• No risk of recall bias As the prospective study
  does not require any data recollection from the
  past, the risk of recall bias is eliminated.

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What are the Various Types of Prospective Studies?

• Prospective trend studies In this study, the
  samples are taken from the dynamic population in
  which the individuals change over time.
• Prospective panel studies In such studies, the
  measurement is done on the same set of
  individuals.
• Prospective cohort studies In the prospective
  cohort studies, the measurement is done on the
  individuals from the same pool of individuals.

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What is the Difference between Retrospective and
Prospective Study?

• Data In the prospective study the data is
  generated by the researcher after enrollment of
  the subjects while retrospective studies make use
  of the already available information.
• Control Prospective study has more control over
  the subjects and data generation as compared to
  retrospective studies.
• Accuracy More accurate results are provided by
  prospective studies due to less biasness and
  optimum data control.

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• Time and cost Prospective studies are more
  time-consuming and costlier as compared to
  retrospective studies.
• Biasness The risk of recall biasness is
  eliminated in prospective studies.
• Practicality Prospective studies are both
  observational and interventional while
  retrospective studies are only observational.
• Usefulness Prospective studies are useful in
  cases of emerging new exposures while
  retrospective studies are not of much use in such
  scenarios.

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