Introduction to study designs - case-control studies Introduction Learning objectives:
Case Control Study Definition A study that compares patients who have a disease or outcome of interest cases with patients who do not have the disease or outcome controlsand looks back retrospectively to compare how frequently the exposure to a risk factor is present in each group to determine the relationship between the risk factor and the disease.
Case control studies are observational because no intervention is attempted and no attempt is made to alter the course of the disease. The goal is to retrospectively determine the exposure to the risk factor of interest from each of the two groups of individuals: These studies are designed to estimate odds.
Case control studies are also known as "retrospective studies" and "case-referent studies. Controls should be subjects who might have been cases in the study but are selected independent of the exposure.
Cases and controls should also not be "over-matched. Does the study use matching or pairing appropriately to avoid the effects of a confounding variable?
Does it use appropriate inclusion and exclusion criteria? Fictitious Example There is a suspicion that zinc oxide, the white non-absorbent sunscreen traditionally worn by lifeguards is more effective at preventing sunburns that lead to skin cancer than absorbent sunscreen lotions. A case-control study was conducted to investigate if exposure to zinc oxide is a more effective skin cancer prevention measure.
The study involved comparing a group of former lifeguards that had developed cancer on their cheeks and noses cases to a group of lifeguards without this type of cancer controls and assess their prior exposure to zinc oxide or absorbent sunscreen lotions.
This study would be retrospective in that the former lifeguards would be asked to recall which type of sunscreen they used on their face and approximately how often. This could be either a matched or unmatched study, but efforts would need to be made to ensure that the former lifeguards are of the same average age, and lifeguarded for a similar number of seasons and amount of time per season.
Real-life Examples Chambers, C. Selective serotonin-reuptake inhibitors and risk of persistent pulmonary hypertension of the newborn.
New England Journal of Medicine, 6 This study used a matched design, matching infants who had persistent pulmonary hypertension with infants who did not have it, and compared the rates of exposure to SSRIs.
Autoimmune and chronic inflammatory disorders and risk of non-hodgkin lymphoma by subtype. Journal of the National Cancer Institute, 98 1 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.
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.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, we describe these study designs, methodological issues, and provide examples from the plastic surgery literature.
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, we describe these study designs, methodological issues, and provide examples from the plastic surgery literature. Case Control Studies:Patients who already have a certain condition are compared with people who do regardbouddhiste.com control studies are generally designed to estimate the odds (using an odds ratio) of developing the studied condition/disease.
Jun 15, · Case-control studies were traditionally referred to as retrospective studies, due to the nature of the study design and execution (1–12,23,24).
In this study design, researchers identify study participants based on their case status, i.e. diseased or not diseased.
Case series and Case reports consist of collections of reports on the treatment of individual patients or a report on a single patient. Because they are reports of cases and use no control groups to compare outcomes, they have little statistical validity.
Design and Analysis of Case-Control Studies Kyoungmi Kim, Ph.D. Nov 9 & 16, Different types of controls may be used, and they have different limitations. Types of Controls Analysis of Case-Control Studies.