Definition[ edit ] The case—control is a type of epidemiological observational study. In this example, cases might be recruited by using hospital records. Case-control studies also are used for diseases that have long latent periods long durations between exposure and disease manifestation and are ideal when multiple potential risk factors are at play.
Case-control studies are sometimes less valued for being retrospective. Measurement of exposure can be made more comparable by using patients with other diseases as controls, especially if subjects are not told the exact focus of the investigation.
Seasonality in pulmonary tuberculosis among migrant workers entering Kuwait. A confidence interval that includes 1. They are comparatively quick, inexpensive, and easy.
Sometimes researchers enroll multiple control groups. Controls Controls should be chosen who are similar in many ways to the cases.
Public health authorities may consider re-allocation of resources in the period of peak seasonality to minimize the risk of Mycobacterium tuberculosis infection to close contacts in this and comparable settings in the region having similar influx of immigrants from high TB burden countries.
Control moments might be sampled from the same driver say, in the previous week or from other drivers, by sampling other moments of time when they were driving; for each of these control moments, it might be ascertained, via the same mechanism as for the cases, whether they were phoning while driving.
Ascertainment of exposure Many case-control studies ascertain exposure from personal recall, using either a self administered questionnaire or an interview. B and D represent the numbers of users of one type or the other contraceptive at Case control studies in epidemiology cross-section in the middle of the time period.
The case group would consist of all those patients at the hospital who developed post-operative endophthalmitis during a pre-defined period.
Comment Case-control studies may prove an association but they do not demonstrate causation.
One way to understand this is to think of genetic exposures. Choosing from a population with a disease different from the one of interest but of similar impact or incidence may minimize recall and measurement bias, since affected individuals may be more likely to recall exposures or to have had their information recorded to a level comparable to cases.
Advantages and Disadvantages Advantages.
An alternative may be to enroll community controls, people from the same neighborhoods as the cases. That is in part because known cases can be compared with selected controls as opposed to waiting for cases to emerge, which is required by other observational study designs and in part because of the rare disease assumption, in which OR mathematically becomes an increasingly better approximation of relative risk as disease incidence declines.
In an African study to evaluate the efficiency of BCG immunisation in preventing tuberculosis, history of inoculation was established by looking for a residual scar on the upper arm. They are particularly appropriate for 1 investigating outbreaks, and 2 studying rare diseases or outcomes.
Journal of the National Cancer Institute, 98 1 Although it may not always be possible, it is important to try to mask the outcome from the person who is collecting risk factor information or interviewing patients.
The selected control group must be at similar risk of developing the outcome; it would not be appropriate to compare a group of controls who had traumatic corneal lacerations with cases who underwent elective intraocular surgery.
The results may be confounded by other factors, to the extent of giving the opposite answer to better studies. The time axis is calendar time. This study matched patients with non-Hodgkin lymphoma NHL with control subjects and compared their history of autoimmune and chronic inflammatory disorders, markers of severity, and treatment.
Case-control and cross sectional studies Chapter 8. In the denominator, we find the proportion of woman-years on the pill divided by the proportion of woman-years of non-use.
Factors found to be significantly more common in the study group included onset before 1 year of age, high seizure frequency at onset, positive history of neonatal seizures, developmental delay and status epilepticus, neurological deficits, and abnormal brain imaging results. However, their exposures may be unrepresentative.
The bold undulating lines show the increasing use of one type of oral contraceptives and the decreasing use of the other type during the time period risk period. During the analysis of study data, multivariate analysis usually logistic regression can be used to adjust for the effect of measured confounders.
Confounders Matching controls to cases will mitigate the effects of confounders. Over the course of three bronchiolitis seasons December to Maythe authors recruited 96 infants mean age, 4. Comparison of prevalence, case history and incidence data in assessing the potency of risk factors in coronary heart disease.
Healthy controls, for example, may not have been seen by a physician for a particular illness or may not remember the details of their illness. American Journal of Epidemiology By and large, as with blood groups, the population denominator remains constant in terms of its exposure distributions: Clinical predictors of intractable childhood epilepsy This case study illustrates the principles taught in Lecture by Annette Gerritsen, Ph.D.
Two designs commonly used in epidemiology are the cohort and case-control studies. Both study causal relationships between a. Case–control studies are one of the fundamental designs utilized in epidemiologic studies Case-control study.
Case-control studies start with the outcome of interest, for example, a disease, and then look backward in time to detect possible causes or risk factors for that disease. Case-control studies can be classified as retrospective (dealing with a past exposure) or prospective (dealing with an anticipated exposure), depending on when cases are identified in relation to the measurement of exposures.
The case-control study was first used in its modern form in Case-control studies cannot provide any information about the incidence or prevalence of a disease because no measurements are made in a population based sample.
Risk Factors and Sampling Another use for case-control studies is investigating risk factors for a rare disease, such as uveal melanoma. Case Control Studies in CVD Epidemiology As Oppenheimer has discussed in his historical background of CVD epidemiology, the field emerged with almost exclusive use of prospective designs for observational studies of risk, in contrast to the case-control approach that dominated the origins of cancer epidemiology (Oppenheimer ).
ERIC at the UNC CH Department of Epidemiology Medical Center Case-Control Studies E R I C N O T E B O O K S E R I E S Case-control studies are used to determine if there is an association.Download