Methods and results from the genome-wide association group at GAW20

Background: This paper summarizes the contributions from the Genome-wide Association Study group (GWAS group) of the GAW20. The GWAS group contributions focused on topics such as association tests, phenotype imputation, and application of empirical kinships. The goals of the GWAS group contributions were varied. A real or a simulated data set based on the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) study was employed by different methods. Different outcomes and covariates were considered, and quality control procedures varied throughout the contributions. Results: The consideration of heritability and family structure played a major role in some contributions. The inclusion of family information and adaptive weights based on data were found to improve power in genome-wide association studies. It was proven that gene-level approaches are more powerful than single-marker analysis. Other contributions focused on the comparison between pedigree-based kinship and empirical kinship matrices, and investigated similar results in heritability estimation, association mapping, and genomic prediction. A new approach for linkage mapping of triglyceride levels was able to identify a novel linkage signal. Conclusions: This summary paper reports on promising statistical approaches and findings of the members of the GWAS group applied on real and simulated data which encompass the current topics of epigenetic and pharmacogenomics

Control procedures and estimators of the false discovery rate and their application in low-dimensional settings: an empirical investigation

Background: When many (up to millions) of statistical tests are conducted in discovery set analyses such as genome-wide association studies (GWAS), approaches controlling family-wise error rate (FWER) or false discovery rate (FDR) are required to reduce the number of false positive decisions. Some methods were specifically developed in the context of high-dimensional settings and partially rely on the estimation of the proportion of true null hypotheses. However, these approaches are also applied in low-dimensional settings such as replication set analyses that might be restricted to a small number of specific hypotheses. The aim of this study was to compare different approaches in low-dimensional settings using (a) real data from the CKDGen Consortium and (b) a simulation study. Results: In both application and simulation FWER approaches were less powerful compared to FDR control methods, whether a larger number of hypotheses were tested or not. Most powerful was the q-value method. However, the specificity of this method to maintain true null hypotheses was especially decreased when the number of tested hypotheses was small. In this low-dimensional situation, estimation of the proportion of true null hypotheses was biased. Conclusions: The results highlight the importance of a sizeable data set for a reliable estimation of the proportion of true null hypotheses. Consequently, methods relying on this estimation should only be applied in high-dimensional settings. Furthermore, if the focus lies on testing of a small number of hypotheses such as in replication settings, FWER methods rather than FDR methods should be preferred to maintain high specificity

Gallstones, Body Mass Index, C-Reactive Protein, and Gallbladder Cancer: Mendelian Randomization Analysis of Chilean and European Genotype Data

BACKGROUND AND AIMS: Gallbladder cancer (GBC) is a neglected disease with substantial geographical variability: Chile shows the highest incidence worldwide, while GBC is relatively rare in Europe. Here, we investigate the causal effects of risk factors considered in current GBC prevention programs as well as C-reactive protein (CRP) level as a marker of chronic inflammation. APPROACH AND RESULTS: We applied two-sample Mendelian randomization (MR) using publicly available data and our own data from a retrospective Chilean and a prospective European study. Causality was assessed by inverse variance weighted (IVW), MR-Egger regression, and weighted median estimates complemented with sensitivity analyses on potential heterogeneity and pleiotropy, two-step MR, and mediation analysis. We found evidence for a causal effect of gallstone disease on GBC risk in Chileans (P = 9 × 10−5) and Europeans (P = 9 × 10−5). A genetically elevated body mass index (BMI) increased GBC risk in Chileans (P = 0.03), while higher CRP concentrations increased GBC risk in Europeans (P = 4.1 × 10−6). European results suggest causal effects of BMI on gallstone disease (P = 0.008); public Chilean data were not, however, available to enable assessment of the mediation effects among causal GBC risk factors. CONCLUSIONS: Two risk factors considered in the current Chilean program for GBC prevention are causally linked to GBC risk: gallstones and BMI. For Europeans, BMI showed a causal effect on gallstone risk, which was itself causally linked to GBC risk. (Hepatology 2021;73:1783-1796).Fil: Barahona Ponce, Carol. Ruprecht Karls Universitat Heidelberg; Alemania. Universidad de Chile; ChileFil: Scherer, Dominique. Ruprecht Karls Universitat Heidelberg; AlemaniaFil: Brinster, Regina. Ruprecht Karls Universitat Heidelberg; AlemaniaFil: Boekstegers, Felix. Ruprecht Karls Universitat Heidelberg; AlemaniaFil: Marcelain, Katherine. Universidad de Chile; ChileFil: Gárate Calderón, Valentina. Ruprecht Karls Universitat Heidelberg; Alemania. Universidad de Chile; ChileFil: Müller, Bettina. Instituto Nacional del Cáncer; ChileFil: de Toro, Gonzalo. Hospital Puerto Montt; Chile. Universidad Austral de Chile; ChileFil: Retamales, Javier. Instituto Nacional del Cáncer; ChileFil: Barajas, Olga. Universidad de Chile; ChileFil: Ahumada, Monica. Universidad de Chile; ChileFil: Morales, Erik. Hospital Regional de Talca; Chile. Universidad Católica del Maule; ChileFil: Rojas, Armando. Universidad Católica del Maule; ChileFil: Sanhueza, Verónica. Hospital Padre Hurtado; ChileFil: Loader, Denisse. Hospital Padre Hurtado; ChileFil: Rivera, María Teresa. Hospital del Salvador; ChileFil: Gutiérrez, Lorena. Hospital San Juan de Dios; ChileFil: Bernal, Giuliano. Universidad Católica del Norte; ChileFil: Ortega, Alejandro. Hospital Regional; ChileFil: Montalvo, Domingo. Hospital Regional Juan Noé Crevani; ChileFil: Portiño, Sergio. Universidad de Chile; ChileFil: Bertrán, Maria Enriqueta. Ministerio de Salud; ChileFil: Gabler, Fernando. Universidad de Santiago de Chile. Hospital Clinico San Borja Arriaran; ChileFil: Spencer, Loreto. Hospital Regional Guillermo Grant Benavente; ChileFil: Olloquequi, Jordi. Universidad Autónoma de Chile; ChileFil: Fischer, Christine. Ruprecht Karls Universitat Heidelberg; AlemaniaFil: Jenab, Mazda. International Agency For Research On Cancer; AlemaniaFil: Aleksandrova, Krasimira. German Institute Of Human Nutrition; AlemaniaFil: Katzke, Verena. German Cancer Research Center; AlemaniaFil: Gonzalez-Jose, Rolando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Ciencias Sociales y Humanas; Argentin

Additional file 4 of Control procedures and estimators of the false discovery rate and their application in low-dimensional settings: an empirical investigation

Simulation – Observed estimations of π0 for Storey’s (qv) and Strimmer’s q-value methods (fdr)for β1 = 1 and π0 = 75% (a), 50% (b), 25% (c). (PNG 209 kb

Mental Health Specialist Video Consultations Versus Treatment-as-Usual for Patients With Depression or Anxiety Disorders in Primary Care: Randomized Controlled Feasibility Trial

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Additional file 2 of Control procedures and estimators of the false discovery rate and their application in low-dimensional settings: an empirical investigation

CKDGen study contributions assigned to replication set for illustration of procedures controlling type I error. (DOCX 18 kb

Gallstones, Body Mass Index, C‐Reactive Protein, and Gallbladder Cancer: Mendelian Randomization Analysis of Chilean and European Genotype Data

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