The browser you are using is not supported by this website. All versions of Internet Explorer are no longer supported, either by us or Microsoft (read more here:

Please use a modern browser to fully experience our website, such as the newest versions of Edge, Chrome, Firefox or Safari etc.

Leif Groop

Leif Groop

Principal investigator

Leif Groop

Informed Conditioning on Clinical Covariates Increases Power in Case-Control Association Studies


  • Noah Zaitlen
  • Sara Lindstroem
  • Bogdan Pasaniuc
  • Marilyn Cornelis
  • Giulio Genovese
  • Samuela Pollack
  • Anne Barton
  • Heike Bickeboeller
  • Donald W. Bowden
  • Steve Eyre
  • Barry I. Freedman
  • David J. Friedman
  • John K. Field
  • Leif Groop
  • Aage Haugen
  • Joachim Heinrich
  • Brian E. Henderson
  • Pamela J. Hicks
  • Lynne J. Hocking
  • Laurence N. Kolonel
  • Maria Teresa Landi
  • Carl D. Langefeld
  • Loic Le Marchand
  • Michael Meister
  • Ann W. Morgan
  • Olaide Y. Raji
  • Angela Risch
  • Albert Rosenberger
  • David Scherf
  • Sophia Steer
  • Martin Walshaw
  • Kevin M. Waters
  • Anthony G. Wilson
  • Paul Wordsworth
  • Shanbeh Zienolddiny
  • Eric Tchetgen Tchetgen
  • Christopher Haiman
  • David J. Hunter
  • Robert M. Plenge
  • Jane Worthington
  • David C. Christiani
  • Debra A. Schaumberg
  • Daniel I. Chasman
  • David Altshuler
  • Benjamin Voight
  • Peter Kraft
  • Nick Patterson
  • Alkes L. Price

Summary, in English

Genetic case-control association studies often include data on clinical covariates, such as body mass index (BMI), smoking status, or age, that may modify the underlying genetic risk of case or control samples. For example, in type 2 diabetes, odds ratios for established variants estimated from low-BMI cases are larger than those estimated from high-BMI cases. An unanswered question is how to use this information to maximize statistical power in case-control studies that ascertain individuals on the basis of phenotype (case-control ascertainment) or phenotype and clinical covariates (case-controlcovariate ascertainment). While current approaches improve power in studies with random ascertainment, they often lose power under case-control ascertainment and fail to capture available power increases under case-control-covariate ascertainment. We show that an informed conditioning approach, based on the liability threshold model with parameters informed by external epidemiological information, fully accounts for disease prevalence and non-random ascertainment of phenotype as well as covariates and provides a substantial increase in power while maintaining a properly controlled falsepositive rate. Our method outperforms standard case-control association tests with or without covariates, tests of gene x covariate interaction, and previously proposed tests for dealing with covariates in ascertained data, with especially large improvements in the case of case-control-covariate ascertainment. We investigate empirical case-control studies of type 2 diabetes, prostate cancer, lung cancer, breast cancer, rheumatoid arthritis, age-related macular degeneration, and end-stage kidney disease over a total of 89,726 samples. In these datasets, informed conditioning outperforms logistic regression for 115 of the 157 known associated variants investigated (P-value = 1x10(-9)). The improvement varied across diseases with a 16% median increase in chi(2) test statistics and a commensurate increase in power. This suggests that applying our method to existing and future association studies of these diseases may identify novel disease loci.


  • Genomics, Diabetes and Endocrinology
  • EXODIAB: Excellence of Diabetes Research in Sweden

Publishing year





PLoS Genetics





Document type

Journal article


Public Library of Science


  • Endocrinology and Diabetes



Research group

  • Genomics, Diabetes and Endocrinology


  • ISSN: 1553-7404