Costs are reduced compared to those of a prospective study, since laboratory tests need to be done only on specimens from subjects who are later chosen as cases or as controls. Thus, we will compare the use of case-control weighted targeted Matching in case-control studies ppt likelihood estimation in matched and unmatched designs in an effort to explore which design yields the most information about the marginal causal effect.
A Literature Review There is a large collection of literature devoted to the topic of individual matching in case-control study designs. Disadvantages In the classical case-control design we can never be certain that exposure to the explanatory variable preceded the individual getting the condition.
This may often be the case when matching has only been performed on standard factors such as sex and age group. Case ascertainment system in place: However, one should also note that matched studies discard not only a pool of unmatched controls, but the information in each exposure-concordant case-control pair.
This balance can reduce the variance in the parameters of interest, which improves statistical efficiency. Childhood Asthma and Passive Smoking How would you design a study to evaluate whether passive smoking is a risk factor for childhood asthma?
A discordant pair occurs when the exposure status of case is different than the exposure status of the control. We have selected cases and controls from a population, often an unknown population.
Dynamic populations may be stable over short time periods. Individual matching moves from beneficial to required when variables such as sibship are included in the study Rothman and Greenland, ; Costanza, This may lead to errors in estimating the relationship between a disease and exposure, as well as the incorrect adaptation of emerging medical literature.
Cases and controls should also not be "over-matched. We will compare the use of case-control weighted targeted maximum likelihood estimation in matched and unmatched case-control study designs as we explore which design yields the most information about the marginal causal effect. Sources of controls a Population of defined area b Hospital patients c Probability sample of total population d Neighbors i walk door to door ii phone random digit dialing iii letter carrier routes e Friends or associates of cases f Siblings, spouses or other relatives g Other C.
The development of effective methods to control confounding in analyses may have contributed to the drop in individually matched designs, but they are still quite common. In the classical case-control design, only one response variable can be studied at one time.
Because the numbers of cases and controls are usually balanced either 1: This study looked at the relation between risk of acute myocardial infarction and current or former smoking, type of tobacco, amount smoked, effect of smokeless tobacco, and exposure to secondhand smoke.
Case-control approaches are the most efficient for rare diseases, e. For example, if siblings have been chosen as controls, then each stratum would have just one case and the sibling control; in this situation, an unconditional logistic regression analysis would suffer from problems of sparse data, and Matching in case-control studies ppt logistic regression would be required.
More importantly, if a marginal causal effect is the parameter of interest, conditional logistic regression cannot be used as it can only estimate the conditional odds ratio.
Literature Review Discussion The consensus in the literature indicates that there are very few circumstances where individual matching is indeed warranted.
Respiratory Disease Applications B. Images not copyright InfluentialPoints credit their source on web-pages attached via hypertext links from those images. Hypothetical matched case-control study with matched analysis View this table: Analytic methods for non-matched case-control studies include: When should a case-control approach be used: Each of these cases is then matched to one or more controls based on a variable or variables believed to be a confounder.
Specific Respiratory Disease Applications: They also describe conditional logistic regression to handle all forms of matching as well as the consideration of modification and other potential confounding.
Using a comprehensive set of search criteria we identified 37 matched case-control studies for detailed analysis.
When funding and time constraints are not compatible with a cohort study. So, while some literature cites the purpose of matching as improving validity, later publications Kupper et al.
What are advantages and disadvantages of different study designs? Case control studies are also known as "retrospective studies" and "case-referent studies. Matching is also cited as necessary by many authors when the investigators expect the distribution of the matching variable to differ drastically between the cases and the controls.
Selection of non-random control can be accepted if there really is no subjective choice involved in other words no risk of selection bias, but usually a random element is essential. However, it is always preferable to use incident newly arising cases in a case-control study if at all possible.
For a dynamic population it only reflects the rate ratio if the population is stable. These studies are designed to estimate odds. However, if there is an association between the matching factor and the exposure, then matching will introduce confounding that needs to be controlled for in the analysis.Although matching will tend to improve study efficiency, it is important to note that, unlike with a cohort design, confounding is not automatically controlled by matching in a case-control design.
One needs a statistical analysis that properly accounts for the matching to obtain a valid estimate of effect. Matching (in case control studies). James Stuart, Fernando Simón EPIET Dublin, Remember confounding.
Confounding factor is variable independently associated with exposure of interest outcome that distorts measurement of association.
Control of confounders. In the study. Case control studies are observational because no intervention is attempted and no attempt is made to alter the course of the disease.
A case-control study was conducted to investigate if exposure to zinc oxide is a more effective skin cancer prevention measure. This study used a matched design, matching infants who had persistent.
5 CASE-CONTROL STUDIES CONFOUNDING • Factor associated with both exposure and outcome creates a noncausal association Male Gender Lung Cancer Smoking CASE-CONTROL STUDIES MATCHING • Makes case and control groups more comparable. Answers. Confounding (answer b) was minimised by matching of cases and controls, whereas allocation bias, the ecological fallacy, and recall bias (answers a, c, and d) were not.
This case-control study aimed to evaluate the effectiveness of a monovalent rotavirus vaccination in reducing admissions for rotavirus diarrhoea in children aged under 2. 11/24/ 1 Case‐Control Matching with SPSS: A Tool to Reduce Selection Bias in Common IR Studies Allan Taing, Research Technician, [email protected]Download