Selection of controls in case-control studies pdf file

Reducing participation bias in casecontrol studies. Rr cannot be used to calculate risk in case control studies. Selection bias will occur in cohort studies if the rates of. In the limit, it will be the indicator that can measure. Specific case control related elements of the kccs sample design discussed below include the frequency of sampling, the criteria for matching, and the sampling of cases. To meet criteria for confidence ratings for metrics where and is included, studies must address both conditions where and is stipulated. The key design element of a casecontrol study is the selection of subjects. Read selection of controls in database casecontrol studies. This work is licensed under a creative commons attribution. Mounib thiru satchi blue cross and blue shield of massachusetts, boston, massachusetts abstract a casecontrol study is an observational study in which subjects are classified according to the presence cases or absence controls of the outcome of interest. Case control study cohort study medical humanities. Several design options available in the planning stage of case control studies are examined. This item assesses whether the control series used in the study is derived from the same population as the cases and essentially would have been cases had the outcome been present. Casecontrol studies, oriented from disease to exposure, identify persons with disease and a comparable group of persons without disease controls.

In view of this there are two key principles that should be followed in selecting controls. Pdf control selection methods in recent casecontrol. Introduction to study designs casecontrol studies health. Risk for lyme disease depends on epidemiologic, entomological, and environmental factors, which can all be linked to spatial location. As noted above, it is always useful to think of a casecontrol study as being nested within some sort of a cohort, i. When case control studies were first developed, most were conducted retrospectively, and it is sometimes assumed that the raredisease assumption applies to all case control studies.

A casecontrol study is an observational study in which subjects are classified according to the presence cases or absence controls of the outcome of interest. Designing and conducting analytic studies in the field. Case control studies unc gillings school of global. Selection of controls in database casecontrol studies. Reducing selection bias in casecontrol studies from rare. Selection bias in case control studies selection bias is a particular problem inherent in case control studies, where it gives rise to noncomparability between cases and controls. For epidemiologic matched case control study designs, sas programs were developed to match cases persons with diseaseevent of interest to controls comparison group of persons without diseaseevent of interest. In case control studies, controls estimate the frequency of an exposure in the population under study. Learn vocabulary, terms, and more with flashcards, games, and other study tools.

Welldesigned observational studies have been shown to provide results similar to randomized controlled trials, challenging the belief that observational studies are secondrate. Analysis of case control studies the odds ratio or is used in case control studies to estimate the strength of the association between exposure and outcome. Selection bias unc gillings school of global public health. Participant selection selection, performance biases instructions. Selection bias in casecontrol studies using relatives as the. However, it actually only applies to those case control studies in which controls are sampled only from the nondiseased rather than the whole population. Topics covered include matching, control case ratio, choice of nested case control or casecohort design, twostage sampling, and other methods that can be used for control selection. Sampling racially matched population controls for case. Apr 23, 2009 association studies can focus on candidate genes, a particular genomic region, or adopt a genomewide association approach, each of which has implications for marker selection. The data the diabetes data set used was taken from a casecontrol study 11, which had recorded cases of children under.

Selection bias in case control studies using relatives as the controls. Another, when the case sampling frame is nearly complete, is to link cases to the sampling frame for controls in order to obtain the information needed to model coverage propensity scores. As noted above, it is always useful to think of a case control study as being nested within some sort of a cohort, i. Association studies can focus on candidate genes, a particular genomic region, or adopt a genomewide association approach, each of which has implications for. Sep 12, 2011 we conclude that selection bias in case control selection of subjects from rare disease registries occurs and that this can be overcome through case control matching to minimize bias. Automating the selection of controls in casecontrol. A case control study is a type of study design in epidemiology. The selection of cases and controls seems to be the most difficult question in planning and conducting a case control study and remains essential regarding the practical requirements for all the steps of this kind of epidemiological design. Case control study design is a type of observational study. Control selection methods in recent casecontrol studies conducted as part of infectious disease outbreaks.

If different methods of selection are used for cases and controls the study should be evaluated by someone with a good understanding of the design of case control studies. Using propensity scores to reduce casecontrol selection bias. Controls can be taken from known or unknown study populations. One may start with a group of people with a known exposure and a comparison group control group without the exposure and follow them through time to see what outcomes result, but this does not constitute a casecontrol study. Casecontrol studies, in contrast, are useful when the population is less clearly defined. Topics covered include matching, control case ratio, choice of nested case. The effect of potential problems in obtaining comparable accuracy. Sources of bias 1 selection bias ideally, control group has to be exactly the same as the group of cases except for the presence of disease selection process should ensure that both cases and controls are likely to come from a similar population selection bias occurs when the persons in one group are. Selection bias in casecontrol studies using relatives as. Selection of neighborhood controls for a populationbased. If the methods of control selection are not described, the study should be rejected. Selection bias will occur as a result of the procedure used to select study participants when the selection probabilities of exposed and unexposed cases and controls from the target population are differential and not proportional. Selection of neighborhood controls is important for case control studies of vectorborne disease because the risk for vectorborne diseases, such as lyme disease, is intrinsically linked to geographical location.

One of the most significant triumphs of the casecontrol study was the demonstration of the link between tobacco smoking and lung cancer, by richard doll and bradford hill. Define eligibility criteria for cases and controls 4. If care is taken with definitions, selection of controls, and reducing the potential for bias, case control studies can generate valuable information. Matched case control studies control for confounding by introducing stratification in the design phase of a study. Casecontrol studies are therefore placed low in the hierarchy of evidence. Therefore, application of this technique permits the study of treatment outcomes or natural history within rare disease registries. Robins j, pike m 1990 the validity of casecontrol studies with nonrandom selection of controls. Case control studies are used to identify factors that may contribute to a medical condition by comparing subjects who have that condition the cases with patients who do not have the condition but are otherwise similar the controls purpose of case control studies 1. Cohort studies and case control studies are two primary types of observational studies that aid in evaluating associations between diseases and exposures. Finding controls for case control studies david a grimes, kenneth f schulz use of control comparison groups is a powerful research tool.

Disadvantages of casecontrol studies casecontrol studies do not yield an estimate of rate or risk, as the denominator of these measures is not defined. Glucocorticoids and the risk of glaucoma, journal of clinical epidemiology on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. Specifically, subjects are conditionally enrolled due to the presence cases or absence controls of the outcome, for the purpose of evaluating the relative frequency of exposures and attributes in those with and without the outcome. Etiologic relationships are determined with case control or cohorts. A case control study is an observational study in which subjects are classified according to the presence cases or absence controls of the outcome of interest. In our second paper 1, we apply the principles presented in this paper to the selection of control groups used in casecontrol studies, including population controls, hospital controls, medical practice controls, friend controls, and relative controls. Describe methods of accrual of cases and controls 5. Selection bias in case control studies may occur when. Then the exposure experiences of the two groups are compared.

Mandep a synthesis of classical and recent thinking on the issues involved in selecting controls for case control studies is presented in this and two companion papers s. Cases and controls are patients who are hospitalized or outpatients. Further discussion about the sample design of case control studies can be found in korn and graubard 1999. Thus, some participants have the outcome of interest referred to as cases, whereas others do not have the outcome of interest referred to as controls. Oct 01, 2000 read selection of controls in injury case control studies, annals of epidemiology on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. Established methods of recruiting population controls for. Cases and controls are registered in a cohort study. In this design, participants are selected for the study based on their outcome status. Evaluation of prior primary malignancy as a determinant of uveal melanoma. Selection of controls in injury casecontrol studies deepdyve.