Table Of Content
Case-control studies are beneficial for an initial investigation of a suspected risk factor for a condition. The information obtained from cross-sectional studies then enables researchers to conduct further data analyses to explore any relationships in more depth. A case-control study is a research method where two groups of people are compared – those with the condition (cases) and those without (controls). By looking at their past, researchers try to identify what factors might have contributed to the condition in the ‘case’ group. 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.
Similar articles in PubMed
In causal inference, it is important that the causal question of interest is unambiguously articulated [1]. The causal question should dictate, and therefore be at the start of, investigation. When the target causal quantity, the estimand, is made explicit, one can start to question how it relates to the available data distribution and, as such, form a basis for estimation with finite samples from this distribution.
Frequently asked questions
Case-control studies are advantageous because they require smaller sample sizes and thus fewer resources and less time than other observational studies. The case-control design also is the most practical option for studying exposure related to rare diseases. 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. Pharmacists use knowledge from cohort and case–control studies to inform patients, clinicians, and the general public about drug effects. At a basic level, cohort and case–control studies quantitatively estimate the relation between exposures and outcomes. They represent rigorous study designs for answering drug safety and effectiveness questions, with case–control studies being more prone to bias.
What Is a Case-Control Study? Definition & Examples
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. It grew in popularity in the 1950s following the publication of several seminal case-control studies that established a link between smoking and lung cancer. The first step in a case–control study is to identify the cases through application of explicitly defined inclusion and exclusion criteria. The case-selection process and the data sources from which cases were selected should be described in detail, especially if cases are from a variety of sources, such as hospital and community-based sources.
The risk of melanoma also increased with increase in years of use, hours of use, and sessions. Keep in mind that by definition the case group is chosen because they already possess the attribute of interest. The point of the control group is to facilitate investigation, e.g., studying whether the case group systematically exhibits that attribute more than the control group does.
The methodologic rigour of cohort and case–control studies evaluating drug–outcome associations is advancing, and approaches are being developed and refined that limit the generation of misleading study results. Indeed, both RCTs and observational studies are necessary, and neither is sufficient to learn about the totality of drug effects in the population. They are particularly appropriate for (1) investigating outbreaks, and (2) studying rare diseases or outcomes. An example of (2) would be a study of risk factors for uveal melanoma, or corneal ulcers. Since case-control studies start with people known to have the outcome (rather than starting with a population free of disease and waiting to see who develops it) it is possible to enroll a sufficient number of patients with a rare disease. The practical value of producing rapid results or investigating rare outcomes may outweigh the limitations of case-control studies.
Study of Intended Drug Effects
The 1167 cases - individuals with invasive cutaneous melanoma – were selected from Minnesota Cancer Surveillance System. The 1101 controls were selected randomly from Minnesota State Driver's License list; they were matched for age (+/- 5 years) and sex. In their landmark study, Doll and Hill (1950) evaluated the association between smoking and lung cancer. A case-control study differs from a cross-sectional study because case-control studies are naturally retrospective in nature, looking backward in time to identify exposures that may have occurred before the development of the disease. Since we considered arbitrary intervals between time points and because, in real-world studies, time is never measured in a truly continuous fashion, this does not represent an important limitation for practical purposes. It is however important to note that the intervals between interventions and outcome assessments (in a target trial) are an intrinsic part of the estimand that lies at the start of investigation.
Association of Visfatin gene polymorphism with obesity related metabolic disorders among Pakistani population: a case ... - Nature.com
Association of Visfatin gene polymorphism with obesity related metabolic disorders among Pakistani population: a case ....
Posted: Wed, 27 Dec 2023 08:00:00 GMT [source]
Household environment and genetic factors may be accounted for by enrolling siblings as controls. Even though matching is used to increase the efficiency in case-control studies, it may have its own problems. It may be difficult to fine the exact matching control for the study; we may have to screen many potential enrollees before we are able to recruit one control for each case recruited. For example, in the above mentioned metabolic syndrome and psoriasis, we can decide that for each case enrolled in the study, we will enroll a control that is matched for sex and age (+/- 2 years). Thus, if 40 year male patient with psoriasis is enrolled for the study as a case, we will enroll a year male patient without psoriasis (and who will not be excluded for other reason) as controls. In fact, Wacholder and colleagues have extensively discussed aspects of design of case control studies and selection of controls in their article.
Identification of causal effects in case-control studies
Since the OR is greater than 1, the outcome is more likely in those exposed (those who are diagnosed with metabolic syndrome) compared with those who are not exposed (those who do are not diagnosed with metabolic syndrome). However, we will require confidence intervals to comment on further interpretation of the OR (This will be discussed in detail in the biostatistics section). They can be particularly useful when we are interested in trying to ensure that some of the measurable and non-measurable confounders are relatively equally distributed in cases and controls (such as home environment, socio-economic status, or genetic factors). The next important point in designing a case-control study is the selection of control patients.
Case-control studies are different from cross-sectional studies in that case-control studies compare groups retrospectively while cross-sectional studies analyze information about a population at a specific point in time. Forming an accurate control group can be challenging, so sometimes researchers enroll multiple control groups to bolster the strength of the case-control study. If the exposure is found more commonly in the cases than the controls, the researcher can hypothesize that the exposure may be linked to the outcome of interest. Case Control Studies are prospective in that they follow the cases and controls over time and observe what occurs.
There are of course many more causal contrasts, treatment regimes and estimands conceivable that could be of interest. We argue that also for these estimands, researchers should seek to establish identifiability before they select an estimator. Table 2 gives an overview of identification results for case-control studies with exact pair matching.
This ensures a smooth transition for experienced colorists while offering a user-friendly introduction for beginners. Case Design Corporation (CDC) is a privately owned and operated business serving the industry for over 90 years. The solution provides the ability to collect evidence once and map it across multiple regulations – simplifying compliance to multiple regulations.
Wacholder and colleagues (1992 a, b, and c) have published wonderful manuscripts on design and conduct of case-control of studies in the American Journal of Epidemiology. The data were collected by self administered questionnaires and telephone interviews. The investigators assessed the use of tanning devices (using photographs), number of years, and frequency of use of these devices. They also collected information on other variables (such as sun exposure; presence of freckles and moles; and colour of skin, hair, among other exposures. Supplementary material to ‘Identification of causal effects in case-control studies’.
During the analysis of study data, multivariate analysis (usually logistic regression) can be used to adjust for the effect of measured confounders. A cohort study compares the experience of 2 or more groups of patients who are followed concurrently forward in time (Figure 1). While one may be added if the investigator so chooses, members of the cohort are primarily selected because of a shared characteristic among them. In particular, retrospective cohort studies are designed to follow a group of people with a common exposure or risk factor over time and observe their outcomes. Case-control studies are a type of observational study often used in fields like medical research, environmental health, or epidemiology.
Data sharing is not applicable to this article as no datasets were generated or analysed during the current study. The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article. A case-control study of readmission to the intensive care unit after cardiac surgery. In addition, case-control studies look at a single subject or a single case, whereas longitudinal studies can be conducted on a large group of subjects.
No comments:
Post a Comment