Dr Prasanth V
Editor, JPID
Evidence Pyramid
‘Evidence pyramid’ can better be termed as ‘evidence
based pyramid’. Background information pertaining to any
topic can be gathered mainly from available literatures. We
have different methods to gather as much information we
want. Some of the gathered information will be unfiltered.
We will come across researches done using different study
designs and each design has its own inherent strengths
and weaknesses.
Quality and reliability of evidence is very important and
for that reason, evidence pyramid is divided into many
levels. Accuracy will be more and bias will be less as we
ascend up the pyramid.
In-vitro lab studies forms the base of the pyramid, above
which Animal Studies are placed. Background information and opinions form the third tier and these information may
not be true always and can get influenced by many factors. 
Case reports and case series forms the immediate higher
level. Many rare diseases were first recognized from case
reports; a glaring example being the early confirmation
of Nipah virus infection in Kerala, India during 2021. But
the scientific community is sceptical about the quality of
evidence obtaining from case report/series.
Case Control study comes just above case report/series.
Absence of randomization and probability of confounding
are often regarded as drawbacks.
Cohort Study is useful is assessing risk factors that cannot
be experimentally controlled. Reliability is more for cohort
studies and the evidence can be generalized more readily.
In evidence pyramid, cohort study comes just above case
control studies.
Evidence from a Randomized Control Trial (RCT), due
to the randomization and its experimental design is a
strongest indicator of a cause and effect relation.
Critical appraisal is a short summaries of available
evidence. Even though not a study design, critical appraisal
is considered as a better evidence provider than RCTs
and sometimes it is included in the evidence pyramid.
Systematic review and meta-analysis at the pinnacle
of the pyramid. They are often regarded as strongest
evidence available in the literature. Critical appraisal,
systematic review and metanalysis are often considered
as ‘filtered information’.