Case-control (case-control, case-controlled) studies are beginning to appear more frequently in the neurosurgical literature.They can be more robust, if well designed, than the typical case series or even cohort study to determine or refine treatment algorithms.
This concept can be illustrated with a standard 2 × 2 table.
In a cohort study, both incidence and RR (or risk ratio) can be calculated by a/(a b) and [a/(a b)]/[c/(c d)], respectively.
These 2 groups are often mislabeled as “cases” and “controls.” A key distinction of cohort studies from case-control studies is that the former may be conducted prospectively and can answer questions about disease incidence.
This difference underlies the different types of questions that can be answered using each design.
For example, if our clinical question was focused upon whether we should be treating patients with odontoid fractures differently if they were older, our research question would be: if the patients who are treated with halo vest apparatuses and who fail to fuse are compared to the patients who do fuse within that treatment population, do those with nonunions tend to be older?
In order to address this question using a cohort study design, a large sample size would be necessary, which is prohibitive when studying rare conditions such as this.The other kind of comparative, predominantly retrospective, study with which the case-control is confused is the cohort study.This contrasts with the case-control study in that the groups treated in two different fashions are then compared for frequency of the outcome of interest.This question could be answered (in fact, most certainly would have to be answered) within a nested case-control design.This was carried out by Lennarson et al as illustrated in Figure 3.The purpose of this review is to define and explore the differences between case-control studies and other so-called nonexperimental, quasiexperimental, or observational studies in determining preferred treatments for neurosurgical patients. Impediments to the successful execution of RCTs include cumbersome study protocols, high cost, lengthy duration, and difficulty enrolling an adequate number of patients.clinical trials aimed at clinical questions outside of drugs and devices have dropped dramatically.Checklists referenced in this algorithm can be found at the Scottish Intercollegiate Guidelines Network (SIGN)Algorithm for determining study design under review for readers (including reviewers).Checklists referenced in this algorithm can be found at the Scottish Intercollegiate Guidelines Network (SIGN)Case-control studies are also differentiated by how findings are reported and the statistics used to analyze data.These studies provide an estimate of the strength of association between a variable and an outcome of interest in the form of an odds ratio (OR).If the outcome of interest is rare and both the controls and the cases are at low risk for developing the outcome, the OR can approximate the relative risk (RR) demonstrating a stronger association and inference of causality.