title: What we don't know can hurt us: Nonresponse bias assessment in birth defects research.
abstract: BACKGROUND
  Nonresponse bias assessment is an important and underutilized tool in survey research to assess potential bias due to incomplete participation. This study illustrates a nonresponse bias sensitivity assessment using a survey on perceived barriers to care for children with orofacial clefts in North Carolina.
  
  
  METHODS
  Children born in North Carolina between 2001 and 2004 with an orofacial cleft were eligible for inclusion. Vital statistics data, including maternal and child characteristics, were available on all eligible subjects. Missing 'responses' from nonparticipants were imputed using assumptions based on the distribution of responses, survey method (mail or phone), and participant maternal demographics.
  
  
  RESULTS
  Overall, 245 of 475 subjects (51.6%) responded to either a mail or phone survey. Cost as a barrier to care was reported by 25.0% of participants. When stratified by survey type, 28.3% of mail respondents and 17.2% of phone respondents reported cost as a barrier. Under various assumptions, the bias-adjusted estimated prevalence of cost as barrier to care ranged from 16.1% to 30.0%. Maternal age, education, race, and marital status at time of birth were not associated with subjects reporting cost as a barrier.
  
  
  CONCLUSIONS
  As survey response rates continue to decline, the importance of assessing the potential impact of nonresponse bias has become more critical. Birth defects research is particularly conducive to nonresponse bias analysis, especially when birth defect registries and birth certificate records are used. Future birth defect studies which use population-based surveillance data and have incomplete participation could benefit from this type of nonresponse bias assessment. Birth Defects Research (Part A) 103:603-609, 2015. © 2015 Wiley Periodicals, Inc.
authors.affiliation: Department of Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.|National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Paula D
authors.initials: PD
authors.lastname: Strassle
authors.affiliation: National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Cynthia H
authors.initials: CH
authors.lastname: Cassell
authors.affiliation: National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Stuart K
authors.initials: SK
authors.lastname: Shapira
authors.affiliation: National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Sarah C
authors.initials: SC
authors.lastname: Tinker
authors.affiliation: North Carolina Birth Defects Monitoring Program, State Center for Health Statistics, North Carolina Division of Public Health, Raleigh, North Carolina.|Department of Maternal and Child Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Meyer
authors.affiliation: National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Scott D
authors.initials: SD
authors.lastname: Grosse
mesh_terms: D015982:Bias; D002971:Cleft Lip; D002972:Cleft Palate; D006801:Humans; D009657:North Carolina
keywords: barriers to care; nonresponse bias; orofacial clefts; response rates