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Data Analysis Plan
Published in Lisa Chasan-Taber, Writing Grant Proposals in Epidemiology, Preventive Medicine, and Biostatistics, 2022
Comparing the characteristic of cases versus controls, in the context of a case-control study, can help to assess whether the control population adequately represents the source population that led to the cases. Remember not to include your exposure of interest in this table, as you would not want or expect it to be similar between the two groups. Instead, evaluating whether the exposure odds differ between the cases and controls will address the primary specific aim of a case-control study.
Comparing Populations
Published in Gary L. Rosner, Purushottam W. Laud, Wesley O. Johnson, Bayesian Thinking in Biostatistics, 2021
Gary L. Rosner, Purushottam W. Laud, Wesley O. Johnson
The type of data in the previous subsection involved sampling individuals from two distinct populations or classifying them into two distinct populations. As previously mentioned, we often refer to the population status as an explanatory factor. We are always interested in how the probabilities of a particular event that is of some consequence will vary as a function of the explanatory factor. However, in this section, we reverse the roles of explanatory factor and event of interest for practical reasons. In a case-control study, the investigators choose individuals based on case or control status and then examine exposure. With the type of data considered here, it is difficult to estimate , for example. But we will be able to estimate the odds ratio
Critical appraisal of retrospective studies
Published in O. Ajetunmobi, Making Sense of Critical Appraisal, 2021
Generally, control subjects (matched or unmatched) should ideally be selected from a similar source as the case subjects. This is because systematic differences can occur between groups that have been selected from different sources. Increasingly, people with a different type of disorder are being used as control subjects in retrospective case-control studies. The purpose of using ‘ill control subjects’ is to reduce the impact of recall bias on study results. Often a case-control study will have two (or more) sets of controls, such as one hospital-based and the other a population-based. This is often performed to increase the validity of eventual result findings.
Social determinants associated with loss of an eye in the United States using the All of Us nationwide database
Published in Orbit, 2022
Alison X. Chan, Bharanidharan Radha Saseendrakumar, Daniel J. Ozzello, Michelle Ting, Jin Sook Yoon, Catherine Y. Liu, Bobby S. Korn, Don O. Kikkawa, Sally L. Baxter
A major strength of using the All of Us database is the enrollment of underrepresented minorities. This is especially relevant given that African Americans and Hispanics are historically underrepresented in ophthalmology research and clinical trials.29 As a testament to the program’s commitment to diversity, our initial analyses of the database revealed that 21.94% of enrolled adults identified as African American. The national scale of All of Us is an additional strength, as the program has multiple enrollment sites in both academic and community settings across the country. Finally, the All of Us database offers sociodemographic information (i.e. highest attained education level, annual income, etc.) and survey data that are not readily available in routine EHRs. Limitations of this study include the inability to establish a causal relationship due to the case-control study design. Cohort definitions relied upon diagnostic billing codes, and it is possible misclassification or inconsistencies in diagnoses occurred, although this is a limitation common to analyses of claims and EHR data. Clinical notes documenting visual acuity and the severity of injury, tumor invasion, or infection are also not currently available through the database.
Association between Psoriasis Disease and IFN-λ Gene Polymorphisms
Published in Immunological Investigations, 2022
Büşra Yilmaz, Güneş Çakmak Genç, Sevim Karakaş Çelik, Nilgün Solak Tekin, Murat Can, Ahmet Dursun
Statistical analysis was performed using SPSS (version. 19.0; SPSS Inc., Chicago, IL, USA). A post-hoc power calculation was performed using the G-Power software to determine the sample size. A case-control study was conducted. The allelic and genotypic frequencies of the polymorphisms were calculated for both for cases and for controls. Analyses were performed using dominant, additive, and recessive models. Dominance was defined in terms of allele 2 (minor allele) effects. In the dominant allele 2 models, homozygous individuals for allele 1 were compared with carriers of allele 2. In the recessive allele 2 models, homozygous individuals for allele 2 were compared with carriers of allele 1. The χ2 test was used to compare the genotype and allele frequencies of each gene polymorphism in psoriasis patients and controls. The odds ratio (OR) and 95% confidence interval (CI) were calculated to compare psoriasis risk for the alleles and genotypes. The Hardy–Weinberg equilibrium (HWE) test was conducted using Excel (Microsoft Office Excel, Microsoft Corp., Redmond, WA). Data distribution was determined with the Shapiro–Wilk test. Continuous variables were expressed as mean ± standard deviation or median (minimum-maximum). The categorical variables were frequency and percent. Continuous variables were compared using the independent-sample t-test or the Mann–Whitney U-test. P values < .05 were considered statistically significant.
Projection of future numbers of mesothelioma cases in the US and the increasing prevalence of background cases: an update based on SEER data for 1975 through 2018
Published in Critical Reviews in Toxicology, 2022
A usual criticism of the conclusion that the studies described above and others like them support the existence of background mesotheliomas is that one or more significant sources of asbestos exposure would have been uncovered for each mesothelioma case if the search for exposure sources was done with greater diligence. However, recall bias mitigates this criticism. Recall bias as it affects estimates of asbestos exposure for mesothelioma is best explained in the context of a case-control study (Siemiatycki and Boffetta 1998; Taubes 1995). In a case-control study, mesothelioma cases are selected from a well-defined population; controls, i.e. individuals who do not have mesothelioma but are considered similar to the cases in all other respects are selected from the same population (Rothman et al. 2008). Statistical methods are used to compare estimates of asbestos exposure levels of the cases to those of the controls to determine if cases had higher asbestos exposure levels than controls, a result that would suggest asbestos causation. However, the claim – if the disease is mesothelioma, the cause is asbestos - was very likely known by the case-control study participants. Therefore, recall bias becomes a factor: mesothelioma cases would expect to find that they had been exposed to asbestos and, as such, a case would likely be more diligent than a control in searching for asbestos exposure to explain why they contracted the disease. Controls would likely be less diligent in their searches for asbestos exposure.