A<unk> <unk> –control (NCC) study is a variation of a<unk> –control study in which<unk> s and controls are drawn from the population in a fully enumerated cohort. Usually, the exposure of interest is only measured among the<unk> s and the selected controls. Thus the<unk>  is more efficient than the full cohort design. The<unk>  can be analyzed using methods for missing covariates. The NCC design is often used when the exposure of interest is difficult or expensive to obtain and when the outcome is rare. By utilizing data previously collected from a large cohort study, the time and cost of beginning a new<unk> –control study is avoided. By only measuring the covariate in as many participants as necessary, the cost and effort of exposure assessment is reduced. This benefit is pronounced when the covariate of interest is biological, since assessments such as gene expression profiling are expensive, and because the quantity of blood available for such analysis is often limited, making it a valuable resource that should not be used unnecessarily.
Nested case–control study
Natural history study
Case–control study
Retrospective cohort study
Randomized controlled trial
Prospective cohort study
Placebo-controlled study
Multicenter trial