Types of medical study
What are the different types of study and analysis used in medical research?
This diagram summarises some of the different types of study and analysis used in medical research. In general, the higher up the pyramid an approach is, the higher the quality of evidence produced by that approach (and the smaller the amount of evidence available).
LABORATORY WORK Work is done in the lab, using test-tubes or animals, to hone the research method and question before moving on to more advanced studies.
CASE SERIES/CASE REPORT Based on the treatment of individual patients and on observation rather than experiment. Even if the data are quantitative (numerical), it is difficult to make any generalisations.
CASE-CONTROL STUDY An observational study that compares individuals who have a particular condition (‘cases’) and those who do not (‘controls’). You can see any correlation, or link, between a particular factor and the disease, but you cannot draw reliable conclusions about any cause.
COHORT STUDY A group of people is monitored over an extended period (often years) to see how changes in one variable aﬀect another – for example, smoking and lung cancer.
RANDOMISED CONTROLLED TRIAL (RCT) Often used in drug testing, RCTs involve the participants being randomly assigned to receive either the treatment under investigation or a placebo (dummy treatment). Known as the ‘gold standard’ for clinical research.
SYSTEMATIC REVIEW AND META-ANALYSIS The strongest evidence. A systematic review collects all the available literature on a particular topic, and meta-analysis is used to combine the numerical outcomes of many separate RCTs.
Source: Based on a diagram from the UNC Health Sciences Library