Table 2.

Definitions of included study designs

Study design	Definition
Analytical studies	Studies that strive to quantify the relationship between a particular exposure or intervention and the outcome of interest, where these studies include a comparison group to compare the outcome rates.23
Systematic review	A study that is conducted systematically to collect all published evidence—that comply with the specified inclusion criteria—and provide a summary of the results to answer a specific research question.117
Randomised controlled trial (RCT)	An experimental study that includes at least two groups—treatment group and control group—to compare the outcomes between the group that received the intervention/drug and the group that received a placebo/no treatment. The participants of the group are randomly allocated to one of the groups.118
Quasi-experimental study/non-RCT	An experimental study that includes at least two groups—treatment group and control group—to compare the outcomes between the group that received the intervention/drug and the group that received a placebo. The participants of the group are not randomly allocated to one of the groups.119
Cohort study	A study that follows a group of people over time, where the participants are sampled based on the presence or absence of a particular exposure to compare the outcome of interest with a control group.118
Case-control study	A study that includes a group of people selected on the outcome of interest (cases) and a group without the outcome of interest (controls), followed by assessing previous exposure of both groups to determine if there is a relationship between the level of exposure and outcome of interest.118
Analytical cross-sectional	A study that looks at two groups—exposed and unexposed—and the outcome of interest at a particular point or period of time to compare the differences between the two groups.118
Descriptive studies	Studies that do not strive to quantify a relationship between variables, but simply describe the disease outcome and characteristics within a defined population. Note that descriptive studies can still include analytic components.23
Prevalence study	A study that looks at a population at a particular point or period of time to describe the prevalence of an outcome of interest.118
Case series	A study where only subjects are included with a particular outcome of interest to describe the shared and diverging characteristics of this study population.120
Case report	A study that describes an unfamiliar or extraordinary outcome of one individual.120