title: Self-reported smoking in online surveys: prevalence estimate validity and item format effects.
abstract: OBJECTIVE
  We assessed validity of self-reported smoking prevalence estimates from an online sample, and explored the impact of different item response formats on estimates.
  
  
  METHODS
  Self-reported current smoking status was obtained from 110,837 respondents from the Harris Poll Online (HPOL) panel from April 2004 to January 2005. Current smoking prevalence was compared with national estimates from the 2004 Behavioral Risk Factor Surveillance System (BRFSS), 2003 National Health Interview Survey (NHIS), and 2001-2002 National Health and Nutrition Examination Survey (NHANES). All estimates were weighted to reflect the US population. A separate survey section measured smoking prevalence using randomly assigned response formats, including yes/no grid, multiple response, numeric box, category grid, and drop-down box formats.
  
  
  RESULTS
  24.0% (95% confidence interval [CI] = 23.7-24.4) of HPOL respondents reported current smoking. BRFSS, NHIS, and NHANES estimates found 20.9%, 21.5% (95% CI = 20.9-22.1), and 24.9% (95% CI = 22.4-27.5), respectively, reporting current smoking. An additional 4.5% of NHANES respondents reporting not smoking had cotinine levels > or =15 ng/mL, indicating current smoking. Estimates of smoking prevalence varied by prevalence period and response format.
  
  
  CONCLUSIONS
  Prevalence estimates obtained from the HPOL panel are comparable to those from national surveys. Online response format choices result in variation in estimated behavioral prevalence. Online surveys may be useful for public health surveillance of the US population.
authors.affiliation: Julius B. Richmond Center of Excellence, American Academy of Pediatrics, University of Rochester Medical Center, 601 Elmwood Avenue, Rochester, NY 14642, USA. jonathan_klein@urms.rochester.edu
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Klein
authors.forename: Randall K
authors.initials: RK
authors.lastname: Thomas
authors.forename: Erika J
authors.initials: EJ
authors.lastname: Sutter
mesh_terms: D005260:Female; D006306:Health Surveys; D006801:Humans; D020407:Internet; D008297:Male; D015995:Prevalence; D015203:Reproducibility of Results; D012907:Smoking / Q000453:epidemiology*; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology