Population controls may also be more difficult to obtain, however, because of lack of interest in participating, and there may be recall biassince population controls are generally healthy and may remember past exposures less accurately.
They are particularly appropriate for 1 investigating outbreaks, and 2 studying rare diseases or outcomes. In theory, the case-control study can be described simply. Because of their efficiency, they may also be ideal for preliminary investigation of a suspected risk factor for a common condition; conclusions may be used to justify a more costly and time-consuming longitudinal study later.
If care is taken with definitions, selection of controls, and reducing the potential for bias, case-control studies can generate valuable information.
Random Digit Dialing Random digit dialing has been popular in the past, but it is becoming less useful because of the use of caller ID, answer machines, and a greater reliance on cell phones instead of land lines. Cohort studies and case-control studies are two primary types of observational studies that aid in evaluating associations between diseases and exposures.
Cross-sectional studies, also known as prevalence studies, examine the data on disease and exposure at one particular time point Figure 2.
In the nested case-control study a control would be selected from the population at risk at the point in time when a case was diagnosed. It is important to calculate a confidence interval for each odds ratio. A confidence interval that includes 1. For statistical reasons, however, there is little gained by including more than two controls per case.
An important technique for adding power to a study is to enroll more than one control for every case. Matching Cases and Controls Although controls must be like the cases in many ways, it is possible to over-match.
In this review article, we describe these study designs, methodological issues, and provide examples from the plastic surgery literature. To address some investigative questions in plastic surgery, randomized controlled trials are not always indicated or ethical to conduct. Occasionally investigators will ask cases to nominate controls who are in one of these categories, because they have similar characteristics, such as genotype, socioeconomic status, or environment, i.
A frequent source of controls is patients from the same hospital who do not have the outcome. An odds ratio without a confidence interval is not very meaningful.
Hospital or Clinic Controls: Case-base sampling also known as "case-cohort" sampling: These factors would only matter if they impacted on the estimate of the proportion of the population who had diabetes.
Anything the researcher can do to minimize this type of bias will strengthen the study. They minimize selection bias because they generally come from the same source population provided referral patterns are similar. Will endophthalmitis have to be proven microbiologically, or will a clinical diagnosis be acceptable?
Case-control studies are sometimes less valued for being retrospective. The goal of analytic studies is to identify and evaluate causes or risk factors of diseases or health-related events.
In contrast, if one enrolled controls from a particular hospital within the geographic area, one would have to at least consider whether the controls were inherently more or less likely to have the exposure of interest.
Women diagnosed with histologically confirmed breast cancer between October and May International Classification of Diseases for Oncology codes C These could include a set of community controls and a set of hospital controls.
A population-based case-control study is one in which the cases come from a precisely defined population, such as a fixed geographic area, and the controls are sampled directly from the same population. They have diseases that are unrelated to the exposure being studied. Case-control and cohort studies offer specific advantages by measuring disease occurrence and its association with an exposure by offering a temporal dimension i.
Instead, observational studies may be the next best method to address these types of questions. However, RCT methodology, which was first developed for drug trials, can be difficult to conduct for surgical investigations.
In the first example above, in which cases were randomly selected from a geographically defined database, the source population is also defined geographically, so it would make sense to select population controls by some random method.
Matching for type of intraocular surgery e. It may be difficult for some people to recall all these details accurately. Comment Case-control studies may prove an association but they do not demonstrate causation.Keywords: observational studies, case-control study, cohort study, Thus in comparison to cohort studies, case-control studies are quick, matched by age and sex in the same hospital and same period.
Controls were of Hans Chinese origin from Jiangsu, China, the same area from where the cases were selected. Advantages and Disadvantages of Case-Control Studies.
Advantages: They are efficient for rare diseases or diseases with a long latency period between exposure and disease manifestation. They are less costly and less time-consuming; they are advantageous when exposure data is expensive or hard to obtain. Hospital or Clinic Controls: The advantages of using controls who are patients from the same facility are: Since case-control studies are often used for uncommon outcomes, investigators often have a limited number of cases but a plentiful supply of potential controls.
Case-control studies: advantages and disadvantages BMJ ; doi: https: It is important that consideration is given to the selection of controls for a case-control study.
Typically, the controls will have had no history of the disease or condition of interest. Case-control studies are not prone to loss to follow-up, unlike cohort.
Epidemiology in Practice: Case-Control Studies. Susan Lewallen, MD and Paul Courtright, Case-control studies have specific advantages compared to other study designs. They are comparatively quick, inexpensive, and easy. These could include a set of community controls and a set of hospital controls.
Advantages of case control studies (3) 1) Reduces number of people needing to be studied Same eligibility criteria as case group 3) Controls need to be as similar to case group as possible, i.e. from same hospital/community.
Random Sampling. Sampling where people are identified from a list of all potential participants.Download