Dr Prasanth V
‘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’.