(observational) Studies in which biomedical and/or health outcomes are assessed in pre-defined groups of individuals. Subjects in the study may receive diagnostic, therapeutic, or other interventions, but the investigator does not assign specific interventions to the subjects of the study.

A type of study in which individuals are observed or certain outcomes are measured. No attempt is made to affect the outcome (for example, no treatment is given).

A work that reports on the results of a clinical study in which participants may receive diagnostic, therapeutic, or other types of interventions, but the investigator does not assign participants to specific interventions (as in an interventional study).

Studies among cancer patients and healthy populations that involve no intervention or alteration in the status of the participants.

Study in which the researchers observe the effect of a risk factor (e.g., exposure), diagnostic test, treatment or other covariate, within a study population, and where the independent variable is not under the control of the researcher. NOTE: Major subtypes of observational studies are cohort study, case-control study, and cross-sectional study.