Retrospective vs Prospective Study
                      Retrospectiv
e vs. 
Prospective 
Study
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.
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. 
 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.
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. 
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.
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.
 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.
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.
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.
 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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