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Emergency Medicine Journal : EMJ Jan 2003Cohort, cross sectional, and case-control studies are collectively referred to as observational studies. Often these studies are the only practicable method of studying... (Review)
Review
Cohort, cross sectional, and case-control studies are collectively referred to as observational studies. Often these studies are the only practicable method of studying various problems, for example, studies of aetiology, instances where a randomised controlled trial might be unethical, or if the condition to be studied is rare. Cohort studies are used to study incidence, causes, and prognosis. Because they measure events in chronological order they can be used to distinguish between cause and effect. Cross sectional studies are used to determine prevalence. They are relatively quick and easy but do not permit distinction between cause and effect. Case controlled studies compare groups retrospectively. They seek to identify possible predictors of outcome and are useful for studying rare diseases or outcomes. They are often used to generate hypotheses that can then be studied via prospective cohort or other studies.
Topics: Case-Control Studies; Cohort Studies; Cross-Sectional Studies; Data Collection; Databases as Topic; Selection Bias
PubMed: 12533370
DOI: 10.1136/emj.20.1.54 -
Plastic and Reconstructive Surgery Dec 2010Observational studies constitute an important category of study designs. To address some investigative questions in plastic surgery, randomized controlled trials are not... (Review)
Review
Observational studies constitute an important category of study designs. To address some investigative questions in plastic surgery, randomized controlled trials are not always indicated or ethical to conduct. Instead, observational studies may be the next best method of addressing these types of questions. Well-designed observational studies have been shown to provide results similar to those of randomized controlled trials, challenging the belief that observational studies are second rate. Cohort studies and case-control studies are two primary types of observational studies that aid in evaluating associations between diseases and exposures. In this review article, the authors describe these study designs and methodologic issues, and provide examples from the plastic surgery literature.
Topics: Bias; Case-Control Studies; Cohort Studies; Evidence-Based Medicine; Humans; Prospective Studies; Randomized Controlled Trials as Topic; Plastic Surgery Procedures; Retrospective Studies
PubMed: 20697313
DOI: 10.1097/PRS.0b013e3181f44abc -
Vaccine Jun 2017Case-control studies are commonly used to evaluate effectiveness of licensed vaccines after deployment in public health programs. Such studies can provide... (Review)
Review
Case-control studies are commonly used to evaluate effectiveness of licensed vaccines after deployment in public health programs. Such studies can provide policy-relevant data on vaccine performance under 'real world' conditions, contributing to the evidence base to support and sustain introduction of new vaccines. However, case-control studies do not measure the impact of vaccine introduction on disease at a population level, and are subject to bias and confounding, which may lead to inaccurate results that can misinform policy decisions. In 2012, a group of experts met to review recent experience with case-control studies evaluating the effectiveness of several vaccines; here we summarize the recommendations of that group regarding best practices for planning, design and enrollment of cases and controls. Rigorous planning and preparation should focus on understanding the study context including healthcare-seeking and vaccination practices. Case-control vaccine effectiveness studies are best carried out soon after vaccine introduction because high coverage creates strong potential for confounding. Endpoints specific to the vaccine target are preferable to non-specific clinical syndromes since the proportion of non-specific outcomes preventable through vaccination may vary over time and place, leading to potentially confusing results. Controls should be representative of the source population from which cases arise, and are generally recruited from the community or health facilities where cases are enrolled. Matching of controls to cases for potential confounding factors is commonly used, although should be reserved for a limited number of key variables believed to be linked to both vaccination and disease. Case-control vaccine effectiveness studies can provide information useful to guide policy decisions and vaccine development, however rigorous preparation and design is essential.
Topics: Case-Control Studies; Control Groups; Female; Humans; Immunization Programs; Immunogenicity, Vaccine; Male; Treatment Outcome; Vaccination; Vaccines
PubMed: 28442231
DOI: 10.1016/j.vaccine.2017.04.037 -
BMJ (Clinical Research Ed.) Feb 2016There are two common misconceptions about case-control studies: that matching in itself eliminates (controls) confounding by the matching factors, and that if matching...
There are two common misconceptions about case-control studies: that matching in itself eliminates (controls) confounding by the matching factors, and that if matching has been performed, then a “matched analysis” is required. However, matching in a case-control study does not control for confounding by the matching factors; in fact it can introduce confounding by the matching factors even when it did not exist in the source population. Thus, a matched design may require controlling for the matching factors in the analysis. However, it is not the case that a matched design requires a matched analysis. Provided that there are no problems of sparse data, control for the matching factors can be obtained, with no loss of validity and a possible increase in precision, using a “standard” (unconditional) analysis, and a “matched” (conditional) analysis may not be required or appropriate.
Topics: Case-Control Studies; Confounding Factors, Epidemiologic; Control Groups; Data Interpretation, Statistical
PubMed: 26916049
DOI: 10.1136/bmj.i969 -
Respiratory Care Oct 2004A retrospective study uses existing data that have been recorded for reasons other than research. A retrospective case series is the description of a group of cases with...
A retrospective study uses existing data that have been recorded for reasons other than research. A retrospective case series is the description of a group of cases with a new or unusual disease or treatment. With a case-control study, cases with and without the condition of interest are identified, and the degree of exposure to a possible risk factor is then retrospectively compared between the 2 groups. With a matched case-control study, control subjects are selected such that they resemble (match) the cases with regards to certain characteristics (eg, age, comorbidity, severity of disease). Retrospective study designs are generally considered inferior to prospective study designs. Therefore, a retrospective study design should never be used when a prospective design is feasible.
Topics: Case-Control Studies; Epidemiologic Studies; Humans; Retrospective Studies
PubMed: 15447798
DOI: No ID Found -
Nature Protocols Sep 2010This protocol details the steps for data quality assessment and control that are typically carried out during case-control association studies. The steps described...
This protocol details the steps for data quality assessment and control that are typically carried out during case-control association studies. The steps described involve the identification and removal of DNA samples and markers that introduce bias. These critical steps are paramount to the success of a case-control study and are necessary before statistically testing for association. We describe how to use PLINK, a tool for handling SNP data, to perform assessments of failure rate per individual and per SNP and to assess the degree of relatedness between individuals. We also detail other quality-control procedures, including the use of SMARTPCA software for the identification of ancestral outliers. These platforms were selected because they are user-friendly, widely used and computationally efficient. Steps needed to detect and establish a disease association using case-control data are not discussed here. Issues concerning study design and marker selection in case-control studies have been discussed in our earlier protocols. This protocol, which is routinely used in our labs, should take approximately 8 h to complete.
Topics: Animals; Case-Control Studies; Computational Biology; Female; Genetic Techniques; Genome-Wide Association Study; Humans; Male; Quality Control
PubMed: 21085122
DOI: 10.1038/nprot.2010.116 -
Journal of Physiotherapy Oct 2017
Topics: Case-Control Studies; Humans; Research Design
PubMed: 28966003
DOI: 10.1016/j.jphys.2017.08.007 -
Statistics in Medicine Dec 2021Typically, case-control studies to estimate odds-ratios associating risk factors with disease incidence only include newly diagnosed cases. Recently proposed methods...
Typically, case-control studies to estimate odds-ratios associating risk factors with disease incidence only include newly diagnosed cases. Recently proposed methods allow incorporating information on prevalent cases, individuals who survived from disease diagnosis to sampling, into cross-sectionally sampled case-control studies under parametric assumptions for the survival time after diagnosis. Here we propose and study methods to additionally use prospectively observed survival times from prevalent and incident cases to adjust logistic models for the time between diagnosis and sampling, the backward time, for prevalent cases. This adjustment yields unbiased odds-ratio estimates from case-control studies that include prevalent cases. We propose a computationally simple two-step generalized method-of-moments estimation procedure. First, we estimate the survival distribution assuming a semiparametric Cox model using an expectation-maximization algorithm that yields fully efficient estimates and accommodates left truncation for prevalent cases and right censoring. Then, we use the estimated survival distribution in an extension of the logistic model to three groups (controls, incident, and prevalent cases), to adjust for the survival bias in prevalent cases. In simulations, under modest amounts of censoring, odds-ratios from the two-step procedure were equally efficient as those estimated from a joint logistic and survival data likelihood under parametric assumptions. This indicates that utilizing the cases' prospective survival data lessens model dependencies and improves precision of association estimates for case-control studies with prevalent cases. We illustrate the methods by estimating associations between single nucleotide polymorphisms and breast cancer risk using controls, and incident and prevalent cases sampled from the US Radiologic Technologists Study cohort.
Topics: Bias; Case-Control Studies; Cohort Studies; Humans; Proportional Hazards Models; Prospective Studies
PubMed: 34510499
DOI: 10.1002/sim.9183 -
Journal of Neuro-ophthalmology : the... Jun 2020
Topics: Anemia; Case-Control Studies; Humans; Neurology; Ophthalmology; Pseudotumor Cerebri
PubMed: 32384417
DOI: 10.1097/WNO.0000000000000970 -
Epidemiology and Psychiatric Sciences Oct 2019Much of our knowledge about the risk factors for suicide comes from case-control studies that either use a psychological autopsy approach or are nested within large...
Much of our knowledge about the risk factors for suicide comes from case-control studies that either use a psychological autopsy approach or are nested within large register-based cohort studies. We would argue that case-control studies are appropriate in the context of a rare outcome like suicide, but there are issues with using this design. Some of these issues are common in psychological autopsy studies and relate to the selection of controls (e.g. selection bias caused by the use of controls who have died by other causes, rather than live controls) and the reliance on interviewing informants (e.g. recall bias caused by the loved ones of cases having thought about the events leading up to the suicide in considerable detail). Register-based studies can overcome some of these problems because they draw upon contain information that is routinely collected for administrative purposes and gathered in the same way for cases and controls. However, they face issues that mean that psychological autopsy studies will still sometimes be the study design of choice for investigating risk factors for suicide. Some countries, particularly low and middle income countries, don't have sophisticated population-based registers. Even where they do exist, there will be variable of interest that are not captured by them (e.g. acute stressful life events that may immediately precede a suicide death), or not captured in a comprehensive way (e.g. suicide attempts and mental illness that do not result in hospital admissions). Future studies of risk factors should be designed to progress knowledge in the field and overcome the problems with the existing studies, particularly those using a case-control design. The priority should be pinning down the risk factors that are amenable to modification or mitigation through interventions that can successfully be rolled out at scale.
Topics: Case-Control Studies; Confounding Factors, Epidemiologic; Control Groups; Humans; Registries; Research Design; Suicide Prevention
PubMed: 31571561
DOI: 10.1017/S2045796019000581