Nonetheless, with careful selection of the match algorithm, match factors, and analysis methods, this design is cost effective and, for our study, yields estimates that are similar to those from a prospective cohort study design.Nested case-control study (NCC) design within a prospective cohort study is used when the outcome data are available for all subjects, but the exposure of interest has not been collected, and is difficult or prohibitively expensive to obtain for all subjects [1,2,3].
If the match procedure is carried out properly, and the selected controls are representative of the controls in the cohort study, then NCC loses little efficiency compared to the full cohort analysis .
NCC could offer better validity than the full cohort study because the match procedure allows for adjustment for both measured, and for unmeasured confounders .
Counter-matched controls are randomly selected from different strata of risk factor exposure levels in order to maximize variation in risk exposures among the controls.
For example, in a study of the risk for bladder cancer from alcohol consumption, you might match cases to controls who smoke different amounts to see if the effect of smoking is only evident at a minimum level of exposure.
Subsequently the use of matching to select the controls allowed for the implementation of the conditional likelihood functions and the demonstration of asymptotic consistency and efficiency property of the risk ratio estimates .
NCC has been used in many biomarker studies where it is expensive to collect and process biological samples for all subjects in the cohort study.Recent applications of NCC include studies showing the effects of serum lipids and lipoproteins on breast cancer risk , urine semaphorin-3A on renal damage in hypertensive patients , DNA methylation markers on type-2 diabetes , and plasma cytokines and the risk of HIV type one .In addition to being cost effective, NCC with a smaller sample size tends to be less computationally demanding than the analysis of the full cohort study.The counter-matched study design is used to specifically assess the impact of this risk factor; it is especially good for assessing the potential interaction (effect modification!) of the secondary risk factor and the primary risk factor.Partial R-square was used to assess the level of overmatching.We found that the optimal match algorithm yielded more matched pairs than the greedy algorithm.Study participants are patients aged over 70 years who underwent scheduled major non-cardiac surgery.The primary outcome was postoperative delirium from in-hospital interviews and medical record review.The nested case-control study (NCC) design within a prospective cohort study is used when outcome data are available for all subjects, but the exposure of interest has not been collected, and is difficult or prohibitively expensive to obtain for all subjects.A NCC analysis with good matching procedures yields estimates that are as efficient and unbiased as estimates from the full cohort study.