title: The validity of self-reported use of hormone replacement therapy among Danish nurses.
abstract: BACKGROUND
  Recent findings from randomized clinical trials on the effects of hormone replacement therapy (HRT) among postmenopausal women contradict findings from observational studies indicating a protective effect on the development of cardiovascular disease. Most observational studies on HRT are based on self-reported data, although data on the validity of HRT in postmenopausal women are sparse.
  
  
  METHODS
  We examined self-reported HRT use from questionnaires administered in 1993 (n = 2694) and again in 1999 (n = 2666) to a cohort of Danish nurses living in two Danish counties compared with prescription-reimbursement data from two administrative databases through the Danish National Health Service.
  
  
  RESULTS
  The sensitivity and specificity of the self-reported, current HRT use in 1993 were 78.4%[95% confidence interval (95% CI) 75.4-81.4] and 98.4% (95% CI 97.8-98.9), respectively. In 1999, the estimates were 74.8% (95% CI 72.0-77.7) and 98.0% (95% CI 97.3-98.8), respectively. None of the factors examined--including age, alcohol intake, physical activity, smoking, presence of hypertension, and body mass index--was strongly associated with validity. We found a relatively high validity of self-reported data on HRT use. Furthermore, agreement between self-reported and registry-based data was not strongly associated with a range of demographic and lifestyle factors.
  
  
  CONCLUSIONS
  These findings suggest that use of self-reported data is not an important contributor to the apparent discrepancy between observational studies and randomized trials on the cardiovascular effects of HRT use.
authors.affiliation: Department of Obstetrics and Gynecology, Hvidovre University Hospital, Denmark.
authors.forename: Ellen Leth
authors.initials: EL
authors.lastname: Løkkegaard
authors.forename: Søren Påske
authors.initials: SP
authors.lastname: Johnsen
authors.forename: Berit Lillienthal
authors.initials: BL
authors.lastname: Heitmann
authors.forename: Claudia
authors.initials: C
authors.lastname: Stahlberg
authors.forename: Anette Tønnes
authors.initials: AT
authors.lastname: Pedersen
authors.forename: Erik Bernhard
authors.initials: EB
authors.lastname: Obel
authors.forename: Yrsa Andersen
authors.initials: YA
authors.lastname: Hundrup
authors.forename: Jesper
authors.initials: J
authors.lastname: Hallas
authors.forename: Henrik Toft
authors.initials: HT
authors.lastname: Sørensen
mesh_terms: D000368:Aged; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D015914:Estrogen Replacement Therapy / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008875:Middle Aged; D009726:Nurses / Q000706:statistics & numerical data; D017698:Postmenopause; D012647:Self-Assessment; D012680:Sensitivity and Specificity; D011795:Surveys and Questionnaires / Q000592:standards*