What term describes subjects in a research study who do not have the disease being studied?

The term that describes subjects in a research study who do not have the disease being studied is "controls." In research, particularly in clinical trials and case-control studies, controls serve as a comparison group against which the characteristics and outcomes of the subjects with the disease can be measured. This comparison helps researchers understand the effect of the disease or an intervention more clearly by providing a baseline of normal or unaffected subjects.

By including controls, researchers can assess differences in exposures, demographics, and outcomes more effectively, which assists in determining the factors associated with the disease. The use of a control group is crucial to minimize bias and confounding, ensuring that the results are attributable to the disease or treatment rather than other variables.

In contrast, the other options suggest different concepts not directly related to subjects without the disease. A case series typically involves a report of a group of patients with a common condition. Studied subjects refer to all individuals involved in the study regardless of their health status. Cross-sectional studies observe a population at a single point in time, often gathering data on both affected and unaffected individuals, rather than defining specific groups like controls.