• Title, Summary, Keyword: case-control studies

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Epstein-Barr Virus and Gastric Cancer Risk: A Meta-analysis With Meta-regression of Case-control Studies

  • Bae, Jong-Myon;Kim, Eun Hee
    • Journal of Preventive Medicine and Public Health
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    • v.49 no.2
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    • pp.97-107
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    • 2016
  • Objectives: Research on how the risk of gastric cancer increases with Epstein-Barr virus (EBV) infection is lacking. In a systematic review that investigated studies published until September 2014, the authors did not calculate the summary odds ratio (SOR) due to heterogeneity across studies. Therefore, we include here additional studies published until October 2015 and conduct a meta-analysis with meta-regression that controls for the heterogeneity among studies. Methods: Using the studies selected in the previously published systematic review, we formulated lists of references, cited articles, and related articles provided by PubMed. From the lists, only case-control studies that detected EBV in tissue samples were selected. In order to control for the heterogeneity among studies, subgroup analysis and meta-regression were performed. Results: In the 33 case-control results with adjacent non-cancer tissue, the total number of test samples in the case and control groups was 5280 and 4962, respectively. In the 14 case-control results with normal tissue, the total number of test samples in case and control groups was 1393 and 945, respectively. Upon meta-regression, the type of control tissue was found to be a statistically significant variable with regard to heterogeneity. When the control tissue was normal tissue of healthy individuals, the SOR was 3.41 (95% CI, 1.78 to 6.51; I-squared, 65.5%). Conclusions: The results of the present study support the argument that EBV infection increases the risk of gastric cancer. In the future, age-matched and sex-matched case-control studies should be conducted.

Sample Size and Statistical Power Calculation in Genetic Association Studies

  • Hong, Eun-Pyo;Park, Ji-Wan
    • Genomics & Informatics
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    • v.10 no.2
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    • pp.117-122
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    • 2012
  • A sample size with sufficient statistical power is critical to the success of genetic association studies to detect causal genes of human complex diseases. Genome-wide association studies require much larger sample sizes to achieve an adequate statistical power. We estimated the statistical power with increasing numbers of markers analyzed and compared the sample sizes that were required in case-control studies and case-parent studies. We computed the effective sample size and statistical power using Genetic Power Calculator. An analysis using a larger number of markers requires a larger sample size. Testing a single-nucleotide polymorphism (SNP) marker requires 248 cases, while testing 500,000 SNPs and 1 million markers requires 1,206 cases and 1,255 cases, respectively, under the assumption of an odds ratio of 2, 5% disease prevalence, 5% minor allele frequency, complete linkage disequilibrium (LD), 1:1 case/control ratio, and a 5% error rate in an allelic test. Under a dominant model, a smaller sample size is required to achieve 80% power than other genetic models. We found that a much lower sample size was required with a strong effect size, common SNP, and increased LD. In addition, studying a common disease in a case-control study of a 1:4 case-control ratio is one way to achieve higher statistical power. We also found that case-parent studies require more samples than case-control studies. Although we have not covered all plausible cases in study design, the estimates of sample size and statistical power computed under various assumptions in this study may be useful to determine the sample size in designing a population-based genetic association study.

No Association between Egg Intake and Prostate Cancer Risk: A Meta-analysis

  • Xie, Bo;He, Huadong
    • Asian Pacific Journal of Cancer Prevention
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    • v.13 no.9
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    • pp.4677-4681
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    • 2012
  • Objective: Egg consumption has been suggested to increase the risk of colorectal and some other cancers. The present study summarized and quantified the current evidence relating dietary intake of eggs and prostate cancer. Materials and methods: Literature searches were conducted to identify peer-reviewed manuscripts published up to July 2012. Twenty manuscripts from nine cohort studies and 11 case-control studies were identified. Summary risk estimates with 95% confidence intervals (CIs) were calculated for case-control and cohort studies separately. Results: Neither the case-control not the cohort studies showed any association of prostate cancer incidence with egg consumption (case-control studies: odds ratio 1.09, 95% CI 0.86-1.31; cohort studies: relative risk 0.97, 95% CI 0.97-1.07). The results were consistent in subgroup analysis. Furthermore, no association was observed between egg consumption and prostate cancer-specific mortality. Conclusions: Our analyses provided no evidence of a significant influence of egg consumption on prostate cancer incidence and mortality. However, more studies, particularly large prospective studies, are needed.

Sample Size and Power Estimation in Case-Control Genetic Association Studies

  • Ahn Chul
    • Genomics & Informatics
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    • v.4 no.2
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    • pp.51-56
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    • 2006
  • In planning a genetic association study, it is necessary to determine the number of samples to be collected for the study in order to achieve sufficient power to detect the hypothesized effect. The case-control design is increasingly used for genetic association studies due to the simplicity of its design. We review the methods for the sample size and power calculations in case-control genetic association studies between a marker locus and a disease phenotype.

Adjusting sampling bias in case-control genetic association studies

  • Seo, Geum Chu;Park, Taesung
    • Journal of the Korean Data and Information Science Society
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    • v.25 no.5
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    • pp.1127-1135
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    • 2014
  • Genome-wide association studies (GWAS) are designed to discover genetic variants such as single nucleotide polymorphisms (SNPs) that are associated with human complex traits. Although there is an increasing interest in the application of GWAS methodologies to population-based cohorts, many published GWAS have adopted a case-control design, which raise an issue related to a sampling bias of both case and control samples. Because of unequal selection probabilities between cases and controls, the samples are not representative of the population that they are purported to represent. Therefore, non-random sampling in case-control study can potentially lead to inconsistent and biased estimates of SNP-trait associations. In this paper, we proposed inverse-probability of sampling weights based on disease prevalence to eliminate a case-control sampling bias in estimation and testing for association between SNPs and quantitative traits. We apply the proposed method to a data from the Korea Association Resource project and show that the standard estimators applied to the weighted data yield unbiased estimates.

DNA Pooling as a Tool for Case-Control Association Studies of Complex Traits

  • Ahn, Chul;King, Terri M.;Lee, Kyusang;Kang, Seung-Ho
    • Genomics & Informatics
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    • v.3 no.1
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    • pp.1-7
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    • 2005
  • Case-control studies are widely used for disease gene mapping using individual genotyping data. However, analyses of large samples are often impractical due to the expense of individual genotyping. The use of DNA pooling can significantly reduce the number of genotyping reactions required; hence reducing the cost of large-scale case-control association studies. Here, we discuss the design and analysis of DNA pooling genetic association studies.

Chronic Hepatitis B Virus Infection and Risk of Pancreatic Cancer: A Meta-analysis

  • Li, Lei;Wu, Bo;Yang, Li-Bo;Yin, Guan-Cheng;Liu, Ji-Yong
    • Asian Pacific Journal of Cancer Prevention
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    • v.14 no.1
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    • pp.275-279
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    • 2013
  • Objectives: A number of studies have shown that chronic hepatitis B virus infection is implicated in susceptibility to pancreatic cancer. However, the results are still controversial. This meta-analysis aimed to quantitatively assess the relationship between chronic hepatitis B virus infection and incidence of pancreatic cancer of cohort and case-control studies. Methods: A literature search was performed for entries from 1990 to 2012 using PUBMED and EMBASE. Studies were included if they reported odds ratios (ORs) and corresponding 95% CIs of pancreatic cancer with respect to the infection of hepatitis B virus. Results: Eight studies met the inclusion criteria, which included five case-control studies and three cohort studies. Compared with individuals who have not infection of hepatitis B virus, the pooled OR of pancreatic cancer was 1.403 (95%CI: 1.139-1.729, P=0.001) for patients with hepatitis B virus infection. Sub-group analysis by study design showed that the summary OR was 1.43 (95%CI: 1.06-1.94, P=0.021) when pooling case-control studies and 1.31 (95%CI: 1.00-1.72, P=0.05) when pooling cohort studies. Conclusion: Findings from this meta-analysis suggest that chronic hepatitis B virus infection may increase the risk of pancreatic cancer. This relationship needs to be confirmed by further follow-up studies.

A review of analysis methods for secondary outcomes in case-control studies

  • Schifano, Elizabeth D.
    • Communications for Statistical Applications and Methods
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    • v.26 no.2
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    • pp.103-129
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    • 2019
  • The main goal of a case-control study is to learn the association between various risk factors and a primary outcome (e.g., disease status). Particularly recently, it is also quite common to perform secondary analyses of the case-control data in order to understand certain associations between the risk factors of the primary outcome. It has been repeatedly documented with case-control data, association studies of the risk factors that ignore the case-control sampling scheme can produce highly biased estimates of the population effects. In this article, we review the issues of the naive secondary analyses that do not account for the biased sampling scheme, and also the various methods that have been proposed to account for the case-control ascertainment. We additionally compare the results of many of the discussed methods in an example examining the association of a particular genetic variant with smoking behavior, where the data were obtained from a lung cancer case-control study.

Alcohol Intake and Risk of Thyroid Cancer: A Meta-Analysis of Observational Studies

  • Hong, Seung-Hee;Myung, Seung-Kwon;Kim, Hyeon Suk;The Korean Meta-Analysis (KORMA) Study Group
    • Cancer Research and Treatment
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    • v.49 no.2
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    • pp.534-547
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    • 2017
  • Purpose The purpose of this study was to assess whether alcohol intake is associated with the risk of thyroid cancer by a meta-analysis of observational studies. Materials and Methods We searched PubMed and EMBASE in June of 2015 to locate eligible studies. We included observational studies such as cross-sectional studies, case-control studies, and cohort studies reporting odd ratios (ORs) or relative risk (RRs) with 95% confidence intervals (CIs). Results We included 33 observational studies with two cross-sectional studies, 20 case-controls studies, and 11 cohort studies, which involved a total of 7,725 thyroid cancer patients and 3,113,679 participants without thyroid cancer in the final analysis. In the fixed-effect model meta-analysis of all 33 studies, we found that alcohol intake was consistently associated with a decreased risk of thyroid cancer (OR or RR, 0.74; 95% CI, 0.67 to 0.83; $I^2=38.6%$). In the subgroup meta-analysis by type of study, alcohol intake also decreased the risk of thyroid cancer in both case-control studies (OR, 0.77; 95% CI, 0.65 to 0.92; $I^2=29.5%$; n=20) and cohort studies (RR, 0.70; 95% CI, 0.60 to 0.82; $I^2=0%$; n=11). Moreover, subgroup meta-analyses by type of thyroid cancer, gender, amount of alcohol consumed, and methodological quality of study showed that alcohol intake was significantly associated with a decreased risk of thyroid cancer. Conclusion The current meta-analysis of observational studies found that, unlike most of other types of cancer, alcohol intake decreased the risk of thyroid cancer.

Circulating folate levels and colorectal adenoma: a case-control study and a meta-analysis

  • Park, Yeong Mi;Youn, Jiyoung;Cho, Chang Ho;Kim, Sung Hi;Lee, Jung Eun
    • Nutrition Research and Practice
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    • v.11 no.5
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    • pp.419-429
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    • 2017
  • BACKGROUND/OBJECTIVES: The relationship between folate and colorectal neoplasia remains controversial. We examined the association between serum folate concentrations and colorectal adenomas in a case-control study of Korean adults and conducted a meta-analysis. SUBJECTS/METHODS: Our case-control study included 113 pairs of case and control who underwent colonoscopy and provided blood samples. We used multivariable conditional logistic regression models to obtain the odds ratios and 95% confidence interval (CIs). For meta-analysis, we identified the relevant studies by searching the PubMed database up to February 2017, included our case-control study and combined the study-specific relative risks (RRs) using a random-effects model. RESULTS: In this case-control study, we included 58 men and 55 women with colorectal adenomas and sex and fasting status matched the controls. We did not find any significant association between the serum folate levels and colorectal adenomas in either men or women. For meta-analysis, a total of eleven studies were included in our analysis and classified into two groups; polyp clearance group (PC) for the studies that included participants who underwent endoscopies and had their polyps removed at baseline; and no polyp clearance group (NPC) for the studies that included participants whose histories of endoscopies were unknown or who underwent their first endoscopies. Four PC (1,311 cases and 1,672 non-cases) and eight NPC studies (3,501 cases and 11,347 non-cases) were included. The combined RRs (95% CIs) comparing the bottom with the top categories of circulating folate levels were 1.07 (0.97-1.18) for the NPC group but 1.45 (1.16-1.74) for the PC group. CONCLUSIONS: Low circulating folate levels were associated with new adenoma formation.