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Assessment of systematic effects of methodological characteristics on candidate genetic associations

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Abstract

Candidate genetic association studies have been found to have a low replication rate in the past. Here, we aimed to assess whether aspects of reported methodological characteristics in genetic association studies may be related to the magnitude of effects observed. An observational, literature-based investigation of 511 case–control studies of genetic association studies indexed in 2007, was undertaken. Meta-regression analyses were used to assess the relationship between 23 reported methodological characteristics and the magnitude of genetic associations. The 511 studies had been conducted in 52 countries and were published in 220 journals (median impact factor 5.1). The multivariate meta-regression model of methodological characteristics plus disease category accounted for 17.2 % of the between-study variance in the magnitude of the reported genetic associations. Our findings are consistent with the view that better conducted and better reported genetic association research may lead to less inflated results.

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References

  • Attia J, Thakkinstian A, D’Este C (2003) Meta-analyses of molecular association studies: methodologic lessons for genetic epidemiology. J Clin Epidemiol 56:297–303

    Article  PubMed  Google Scholar 

  • Bogardus ST Jr, Concato J, Feinstein AR (1999) Clinical epidemiological quality in molecular genetic research: the need for methodological standards. JAMA 281:1919–1926

    Article  PubMed  Google Scholar 

  • Borenstein M, Hedges L, Higgins, JPT, Rothstein H (2009) Meta-Analysis, fixed effects vs. random effects. In: Introduction to Meta-analysis. J Wiley & Sons, Chichester, pp. 61–85. Available at http://www.Meta-Analysis.com. Accessed 24 July 2012

  • Brookmeyer R, Liang KY, Linet M (1986) Matched case-control designs and overmatched analyses. Am J Epidemiol 124:693–701

    PubMed  CAS  Google Scholar 

  • Cardon LR, Bell JI (2001) Association study designs for complex diseases. Nat Rev Genet 2:91–99

    Article  PubMed  CAS  Google Scholar 

  • Clark MF, Baudouin SV (2006) A systematic review of the quality of genetic association studies in human sepsis. Intensive Care Med 32:1706–1712

    Article  PubMed  Google Scholar 

  • Committee on Assuring the Health of the Public in the 21st Century (2002) The Future of the Public’s Health in the 21st Century. Institute of Medicine, Washington DC

  • Cooper DN, Nussbaum RL, Krawczak M (2002) Proposed guidelines for papers describing DNA polymorphism-disease associations. Hum Genet 110:207–208

    Article  PubMed  CAS  Google Scholar 

  • Costanza MC (1995) Matching. Prev Med 24:425–433

    Article  PubMed  CAS  Google Scholar 

  • Crow JF (1999) Hardy, Weinberg and language impediments. Genetics 152:821–825

    PubMed  CAS  Google Scholar 

  • DeLisi LE, Faraone SV (2006) When is a “positive” association truly a “positive” in psychiatric genetics? A commentary based on issues debated at the World Congress of Psychiatric Genetics, Boston, October 12–18, 2005. Am J Med Genet B Neuropsychiatr Genet 141B:319–322

    Article  PubMed  Google Scholar 

  • Dickersin K (2002) Systematic reviews in epidemiology: why are we so far behind? Int J Epidemiol 31:6–12

    Article  PubMed  Google Scholar 

  • Dong LM, Potter JD, White E, Ulrich CM, Cardon LR, Peters U (2008) Genetic susceptibility to cancer: the role of polymorphisms in candidate genes. JAMA 299:2423–2436

    Article  PubMed  CAS  Google Scholar 

  • Edwards AW (2008) G. H. Hardy (1908) and Hardy–Weinberg equilibrium. Genetics 179:1143–1150

    Article  PubMed  CAS  Google Scholar 

  • European Bioinformatics Institute (2012) The European Genome-phenome Archive (EGA). Available at https://www.ebi.ac.uk/ega/. Accessed 1 June 2012

  • GAIN Collaborative Research Group, Manolio TA, Rodriguez LL, Brooks L, Abecasis G, Collaborative Association Study of Psoriasis, Ballinger D, Daly M, Donnelly P, Faraone SV, International Multi-Center ADHD Genetics Project, Frazer K, Gabriel S, Gejman P, Molecular Genetics of Schizophrenia Collaboration, Guttmacher A, Harris EL, Insel T, Kelsoe JR, Bipolar Genome Study, Lander E, McCowin N, Mailman MD, Nabel E, Ostell J, Pugh E, Sherry S, Sullivan PF, Major Depression Stage 1 Genomewide Association in Population-Based Samples Study, Thompson JF, Warram J, Genetics of Kidneys in Diabetes (GoKinD) Study, Wholley D, Milos PM, Collins FS (2007) New models of collaboration in genome-wide association studies: the Genetic Association Information Network. Nat Genet 39:1045–1051

    Google Scholar 

  • Gambaro G, Anglani F, D’Angelo A (2000) Association studies of genetic polymorphisms and complex disease. Lancet 355:308–311

    Article  PubMed  CAS  Google Scholar 

  • Garte S, Gaspari L, Alexandrie AK, Ambrosone C, Autrup H, Autrup JL, Baranova H, Bathum L, Benhamou S, Boffetta P, Bouchardy C, Breskvar K, Brockmoller J, Cascorbi I, Clapper ML, Coutelle C, Daly A, Dell’Omo M, Dolzan V, Dresler CM, Fryer A, Haugen A, Hein DW, Hildesheim A, Hirvonen A, Hsieh LL, Ingelman-Sundberg M, Kalina I, Kang D, Kihara M, Kiyohara C, Kremers P, Lazarus P, Le Marchand L, Lechner MC, van Lieshout EM, London S, Manni JJ, Maugard CM, Morita S, Nazar-Stewart V, Noda K, Oda Y, Parl FF, Pastorelli R, Persson I, Peters WH, Rannug A, Rebbeck T, Risch A, Roelandt L, Romkes M, Ryberg D, Salagovic J, Schoket B, Seidegard J, Shields PG, Sim E, Sinnet D, Strange RC, Stucker I, Sugimura H, To-Figueras J, Vineis P, Yu MC, Taioli E (2001) Metabolic gene polymorphism frequencies in control populations. Cancer Epidemiol Biomarkers Prev 10:1239–1248

    PubMed  CAS  Google Scholar 

  • Gelernter J, Goldman D, Risch N (1993) The A1 allele at the D2 dopamine receptor gene and alcoholism. A reappraisal. JAMA 269:1673–1677

    Article  PubMed  CAS  Google Scholar 

  • Genomics, Health and Society Working Group (2004) Genomics, Health and Society. Emerging Issues for Public Policy, Policy Research Initiative, Ottawa. Available at http://www.policy.ca/policy-directory/Detailed/Genomics_-Health-and-Society_-Emerging-Issues-for-Public-Policy-_1_-483.html. ISBN: 0-662-35154-1

  • Gissler M, Hemminki E (1996) The danger of overmatching in studies of the perinatal mortality and birthweight of infants born after assisted conception. Eur J Obstet Gynecol Reprod Biol 69:73–75

    Article  PubMed  CAS  Google Scholar 

  • Hall IP, Blakey JD (2005) Genetic association studies in Thorax. Thorax 60:357–359

    Article  PubMed  CAS  Google Scholar 

  • Hegele RA (2002) SNP judgments and freedom of association. Arterioscler Thromb Vasc Biol 22:1058–1061

    Article  PubMed  CAS  Google Scholar 

  • Higgins JP, Thompson SG (2002) Quantifying heterogeneity in a meta-analysis. Stat Med 21:1539–1558

    Article  PubMed  Google Scholar 

  • Higgins JP, Thompson SG, Deeks JJ, Altman DG (2003) Measuring inconsistency in meta-analyses. BMJ 327:557–560

    Article  PubMed  Google Scholar 

  • Hindorff LA, Sethupathy P, Junkins HA, Ramos EM, Mehta JP, Collins FS, Manolio TA (2009) Potential etiologic and functional implications of genome-wide association loci for human diseases and traits. Proc Natl Acad Sci USA 106:9362–9367

    Article  PubMed  CAS  Google Scholar 

  • Hirschhorn JN, Lohmueller K, Byrne E, Hirschhorn K (2002) A comprehensive review of genetic association studies. Genet Med 4:45–61

    Article  PubMed  CAS  Google Scholar 

  • Huizinga TW, Pisetsky DS, Kimberly RP (2004) Associations, populations, and the truth: recommendations for genetic association studies in Arthritis & Rheumatism. Arthritis Rheum 50:2066–2071

    Article  PubMed  Google Scholar 

  • Ioannidis JP (2003) Genetic associations: false or true? Trends Mol Med 9:135–138

    Article  PubMed  Google Scholar 

  • Ioannidis JP (2005a) Contradicted and initially stronger effects in highly cited clinical research. JAMA 294:218–228

    Article  PubMed  CAS  Google Scholar 

  • Ioannidis JP (2005b) Why most published research findings are false. PLoS Med 2:e124

    Article  PubMed  Google Scholar 

  • Ioannidis JP (2008) Why most discovered true associations are inflated. Epidemiology 19:640–648

    Article  PubMed  Google Scholar 

  • Ioannidis JP, Trikalinos TA (2005) Early extreme contradictory estimates may appear in published research: the Proteus phenomenon in molecular genetics research and randomized trials. J Clin Epidemiol 58:543–549

    Article  PubMed  Google Scholar 

  • Ioannidis JP, Ntzani EE, Trikalinos TA, Contopoulos-Ioannidis DG (2001) Replication validity of genetic association studies. Nat Genet 29:306–309

    Article  PubMed  CAS  Google Scholar 

  • Ioannidis JP, Trikalinos TA, Ntzani EE, Contopoulos-Ioannidis DG (2003) Genetic associations in large versus small studies: an empirical assessment. Lancet 361:567–571

    Article  PubMed  Google Scholar 

  • Ioannidis JP, Gwinn M, Little J, Higgins JP, Bernstein JL, Boffetta P, Bondy M, Bray MS, Brenchley PE, Buffler PA, Casas JP, Chokkalingam A, Danesh J, Smith GD, Dolan S, Duncan R, Gruis NA, Hartge P, Hashibe M, Hunter DJ, Jarvelin MR, Malmer B, Maraganore DM, Newton-Bishop JA, O’Brien TR, Petersen G, Riboli E, Salanti G, Seminara D, Smeeth L, Taioli E, Timpson N, Uitterlinden AG, Vineis P, Wareham N, Winn DM, Zimmern R, Khoury MJ, Human Genome Epidemiology Network and the Network of Investigator Networks (2006) A road map for efficient and reliable human genome epidemiology. Nat Genet 38:3–5

  • Ioannidis JP, Thomas G, Daly MJ (2009) Validating, augmenting and refining genome-wide association signals. Nat Rev Genet 10:318–329

    Article  PubMed  CAS  Google Scholar 

  • Ioannidis JP, Castaldi P, Evangelou E (2010) A compendium of genome-wide associations for cancer: critical synopsis and reappraisal. J Natl Cancer Inst 102:846–858

    Article  PubMed  CAS  Google Scholar 

  • Ioannidis JP, Tarone R, McLaughlin JK (2011) The false-positive to false-negative ratio in epidemiologic studies. Epidemiology 22:450–456

    Article  PubMed  Google Scholar 

  • Khoury MJ, Millikan R, Little J, Gwinn M (2004) The emergence of epidemiology in the genomics age. Int J Epidemiol 33:936–944

    Article  PubMed  Google Scholar 

  • Khoury MJ, Davis R, Gwinn M, Lindegren ML, Yoon P (2005) Do we need genomic research for the prevention of common diseases with environmental causes? Am J Epidemiol 161:799–805

    Article  PubMed  Google Scholar 

  • Khoury MJ, Gwinn M, Burke W, Bowen S, Zimmern R (2007) Will genomics widen or help heal the schism between medicine and public health? Am J Prev Med 33:310–317

    Article  PubMed  Google Scholar 

  • Khoury MJ, Bertram L, Boffetta P, Butterworth AS, Chanock SJ, Dolan SM, Fortier I, Garcia-Closas M, Gwinn M, Higgins JP, Janssens AC, Ostell J, Owen RP, Pagon RA, Rebbeck TR, Rothman N, Bernstein JL, Burton PR, Campbell H, Chockalingam A, Furberg H, Little J, O’Brien TR, Seminara D, Vineis P, Winn DM, Yu W, Ioannidis JP (2009) Genome-wide association studies, field synopses, and the development of the knowledge base on genetic variation and human diseases. Am J Epidemiol 170:269–279

    Article  PubMed  Google Scholar 

  • Lancet editorial (2003) In search of genetic precision. Lancet 361:357

    Google Scholar 

  • Lavedan C, Birznieks G, Dressman M, McCullough K, Paczkowski R, Torres R, Wolfgang C, Polymeropoulos M (2004) Translating the genome into individualized therapeutics. Drug Dev Res 62:371–382

    Article  CAS  Google Scholar 

  • Lawrence RW, Evans DM, Cardon LR (2005) Prospects and pitfalls in whole genome association studies. Philos Trans R Soc Lond B Biol Sci 360:1589–1595

    Article  PubMed  CAS  Google Scholar 

  • Lee W, Bindman J, Ford T, Glozier N, Moran P, Stewart R, Hotopf M (2007) Bias in psychiatric case-control studies: literature survey. Br J Psychiatry 190:204–209

    Article  PubMed  Google Scholar 

  • Little J (2004) Reporting and review of human genome epidemiology studies. In: Khoury MJ, Little J, Burke W (eds) Human genome epidemiology: a scientific foundation for using genetic information to improve health and prevent disease. Oxford University Press, New York, pp 168–192

    Google Scholar 

  • Little J, Higgins JPT (eds) (2006) The HuGENet™ HuGE Review Handbook, version 1.0. Available at http://www.med.uottawa.ca/public-health-genomics/web/assets/documents/HuGE_Review_Handbook_V1_0.pdf. Accessed 20 July 2011

  • Little J, Bradley L, Bray MS, Clyne M, Dorman J, Ellsworth DL, Hanson J, Khoury M, Lau J, O’Brien TR, Rothman N, Stroup D, Taioli E, Thomas D, Vainio H, Wacholder S, Weinberg C (2002) Reporting, appraising, and integrating data on genotype prevalence and gene-disease associations. Am J Epidemiol 156:300–310

    Article  PubMed  Google Scholar 

  • Little J, Higgins JP, Ioannidis JP, Moher D, Gagnon F, von Elm E, Khoury MJ, Cohen B, Davey-Smith G, Grimshaw J, Scheet P, Gwinn M, Williamson RE, Zou GY, Hutchings K, Johnson CY, Tait V, Wiens M, Golding J, van Duijn C, McLaughlin J, Paterson A, Wells G, Fortier I, Freedman M, Zecevic M, King R, Infante-Rivard C, Stewart A, Birkett N (2009) Strengthening the reporting of genetic association studies (STREGA): an extension of the STROBE Statement. Hum Genet 125:131–151

    Article  PubMed  Google Scholar 

  • Lohmueller KE, Pearce CL, Pike M, Lander ES, Hirschhorn JN (2003) Meta-analysis of genetic association studies supports a contribution of common variants to susceptibility to common disease. Nat Genet 33:177–182

    Article  PubMed  CAS  Google Scholar 

  • Mackay J, Taylor A (2006) Moving genetics into clinical cancer care: examples from BRCA gene testing and telemedicine. Breast 15(Suppl 2):S65–S70

    Article  PubMed  Google Scholar 

  • Mailman MD, Feolo M, Jin Y, Kimura M, Tryka K, Bagoutdinov R, Hao L, Kiang A, Paschall J, Phan L, Popova N, Pretel S, Ziyabari L, Lee M, Shao Y, Wang ZY, Sirotkin K, Ward M, Kholodov M, Zbicz K, Beck J, Kimelman M, Shevelev S, Preuss D, Yaschenko E, Graeff A, Ostell J, Sherry ST (2007) The NCBI dbGaP database of genotypes and phenotypes. Nat Genet 39:1181–1186

    Article  PubMed  CAS  Google Scholar 

  • Manolio TA, Brooks LD, Collins FS (2008) A HapMap harvest of insights into the genetics of common disease. J Clin Invest 118:1590–1605

    Article  PubMed  CAS  Google Scholar 

  • Mayo O (2008) A century of Hardy–Weinberg equilibrium. Twin Res Hum Genet 11:249–256

    Article  PubMed  Google Scholar 

  • McCarthy MI, Abecasis GR, Cardon LR, Goldstein DB, Little J, Ioannidis JP, Hirschhorn JN (2008) Genome-wide association studies for complex traits: consensus, uncertainty and challenges. Nat Rev Genet 9:356–369

    Article  PubMed  CAS  Google Scholar 

  • Moher D, Pham B, Klassen TP, Schulz KF, Berlin JA, Jadad AR, Liberati A (2000) What contributions do languages other than English make on the results of meta-analyses? J Clin Epidemiol 53:964–972

    Article  PubMed  CAS  Google Scholar 

  • Nat. Genet editorial (1999) Freely associating. Nat Genet 22:1–2

    Google Scholar 

  • National Institutes of Health (NIH) (2008) NIH Notice on Development of Data Sharing Policy for Sequence and Related Genomic Data. Available at http://grants.nih.gov/grants/guide/notice-files/NOT-HG-10-006.html. Accessed 31 May 2012

  • National Institutes of Health (NIH) (2009) Policy for Sharing of Data Obtained in NIH-Supported or Conducted Genome-Wide Association Studies. Available at http://grants.nih.gov/grants/guide/notice-files/NOT-OD-07-088.html. Accessed 31 May 2012

  • Pan Z, Trikalinos TA, Kavvoura FK, Lau J, Ioannidis JP (2005) Local literature bias in genetic epidemiology: an empirical evaluation of the Chinese literature. PLoS Med 2:e334

    Article  PubMed  Google Scholar 

  • Patsopoulos NA, Analatos AA, Ioannidis JP (2005) Relative citation impact of various study designs in the health sciences. JAMA 293:2362–2366

    Article  PubMed  CAS  Google Scholar 

  • Peters DL, Barber RC, Flood EM, Garner HR, O’Keefe GE (2003) Methodologic quality and genotyping reproducibility in studies of tumor necrosis factor -308 G–>A single nucleotide polymorphism and bacterial sepsis: implications for studies of complex traits. Crit Care Med 31:1691–1696

    Article  PubMed  CAS  Google Scholar 

  • Peterson HB, Kleinbaum DG (1991) Interpreting the literature in obstetrics and gynecology: I. Key concepts in epidemiology and biostatistics. Obstet Gynecol 78:710–717

    PubMed  CAS  Google Scholar 

  • Pham B, Klassen TP, Lawson ML, Moher D (2005) Language of publication restrictions in systematic reviews gave different results depending on whether the intervention was conventional or complementary. J Clin Epidemiol 58:769–776

    Article  PubMed  Google Scholar 

  • Rebbeck TR, Martinez ME, Sellers TA, Shields PG, Wild CP, Potter JD (2004) Genetic variation and cancer: improving the environment for publication of association studies. Cancer Epidemiol Biomarkers Prev 13:1985–1986

    PubMed  Google Scholar 

  • Rosenthal R, DiMatteo MR (2001) Meta-analysis: recent developments in quantitative methods for literature reviews. Annu Rev Psychol 52:59–82

    Article  PubMed  CAS  Google Scholar 

  • Salanti G, Amountza G, Ntzani EE, Ioannidis JP (2005) Hardy–Weinberg equilibrium in genetic association studies: an empirical evaluation of reporting, deviations, and power. Eur J Hum Genet 13:840–848

    Article  PubMed  CAS  Google Scholar 

  • Shastry BS (2005) Genetic diversity and new therapeutic concepts. J Hum Genet 50:321–328

    Article  PubMed  CAS  Google Scholar 

  • Stroup DF, Berlin JA, Morton SC, Olkin I, Williamson GD, Rennie D, Moher D, Becker BJ, Sipe TA, Thacker SB (2000) Meta-analysis of observational studies in epidemiology: a proposal for reporting. Meta-analysis of observational studies in epidemiology (MOOSE) group. JAMA 283:2008–2012

    Article  PubMed  CAS  Google Scholar 

  • Sutton AJ, Higgins JP (2008) Recent developments in meta-analysis. Stat Med 27:625–650

    Article  PubMed  Google Scholar 

  • Tabor HK, Risch NJ, Myers RM (2002) Candidate-gene approaches for studying complex genetic traits: practical considerations. Nat Rev Genet 3:391–397

    Article  PubMed  CAS  Google Scholar 

  • Tan NC, Mulley JC, Berkovic SF (2004) Genetic association studies in epilepsy: “the truth is out there”. Epilepsia 45:1429–1442

    Article  PubMed  CAS  Google Scholar 

  • Thomas DC, Haile RW, Duggan D (2005) Recent developments in genomewide association scans: a workshop summary and review. Am J Hum Genet 77:337–345

    Article  PubMed  CAS  Google Scholar 

  • Trikalinos TA, Salanti G, Khoury MJ, Ioannidis JP (2006) Impact of violations and deviations in Hardy–Weinberg equilibrium on postulated gene-disease associations. Am J Epidemiol 163:300–309

    Article  PubMed  Google Scholar 

  • Trikalinos TA, Salanti G, Zintzaras E, Ioannidis JP (2008) Meta-analysis methods. Adv Genet 60:311–334

    Article  PubMed  Google Scholar 

  • Van Houwelingen HC, Zwinderman KH, Stijnen T (1993) A bivariate approach to meta-analysis. Stat Med 12:2273–2284

    Article  PubMed  Google Scholar 

  • Van Houwelingen HC, Arends LR, Stijnen T (2002) Advanced methods in meta-analysis: multivariate approach and meta-regression. Stat Med 21:589–624

    Article  PubMed  Google Scholar 

  • Vickers A, Goyal N, Harland R, Rees R (1998) Do certain countries produce only positive results? A systematic review of controlled trials. Control Clin Trials 19:159–166

    Article  PubMed  CAS  Google Scholar 

  • Visscher PM, Brown MA, McCarthy MI, Yang J (2012) Five years of GWAS discovery. Am J Hum Genet 90:7–24

    Article  PubMed  CAS  Google Scholar 

  • Wedzicha JN, Hall IP (2005) Genetic association studies in Thorax. Thorax 60:357

    Article  Google Scholar 

  • Wellcome Trust Case Control Consortium (2007) Genome-wide association study of 14,000 cases of seven common diseases and 3,000 shared controls. Nature 447:661–678

    Article  Google Scholar 

  • Yesupriya A, Evangelou E, Kavvoura FK, Patsopoulos NA, Clyne M, Walsh MC, Lin BK, Yu W, Gwinn M, Ioannidis JP, Khoury MJ (2008) Reporting of human genome epidemiology (HuGE) association studies: an empirical assessment. BMC Med Res Methodol 8:31

    Article  PubMed  Google Scholar 

  • Yu W, Yesupriya A, Clyne M, Wulf A, Gwinn M, Khoury MJ (2007) HuGE Literature Finder. HuGE Navigator. Available at: http://www.hugenavigator.net/HuGENavigator/startPagePubLit.do/. Accessed 28 Dec 2007

  • Yu W, Gwinn M, Clyne M, Yesupriya A, Khoury MJ (2008) A navigator for human genome epidemiology. Nat Genet 40:124–125

    Article  PubMed  CAS  Google Scholar 

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Acknowledgments

Diana Fox and Zahra Montazeri for administrative support. Knowledge Translation Branch, Canadian Institutes of Health Research (Grant Ref No: 200606KRS-162113-KRS-CECA-102805); Biotechnology, Genomics and Population Health Branch, Public Health Agency of Canada. National Guard Health Affairs, Saudi Arabia. Julian Little holds a Canada Research Chair in Human Genome Epidemiology. The funders had no role in the decision to submit the article or in its preparation.

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Aljasir, B., Ioannidis, J.P.A., Yurkiewich, A. et al. Assessment of systematic effects of methodological characteristics on candidate genetic associations. Hum Genet 132, 167–178 (2013). https://doi.org/10.1007/s00439-012-1237-4

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