title: Recruiting blacks to the Adventist health study: Do follow-up phone calls increase response rates?
abstract: OBJECTIVE
  To determine whether follow-up phone calls improve response rates to a long questionnaire among black and white subjects.
  
  
  METHODS
  Forty black and 39 white Seventh-day Adventist churches were randomized to experimental or control status in a 2:1 ratio favoring the intervention, which is a follow-up phone call to certain church members. Subjects selected from each church were those who had signed up for the Adventist Health Study-2 but not returned a questionnaire 3 months after promotion began. Further returns from a church over the next 3 months, and this increment as a proportion of baseline response, were assessed using t-tests and Poisson regression, respectively.
  
  
  RESULTS
  Comparing black experimental and control churches, the mean difference was 5.5 returned questionnaires per church (p < 0.01). Among white churches the mean difference was 3.0 (ns). The baseline-adjusted increment, however, was greater by a factor of 3.37 (95% confidence interval, 1.92, 5.93) in the black experimental relative to control churches, but among white experimental churches was 13% (ns) lower than controls. This difference in response by ethnic group was statistically significant (p < 0.01).
  
  
  CONCLUSIONS
  Follow-up phone calls improved response rates among black subjects only.
authors.affiliation: Loma Linda University School of Public Health, Loma Linda, CA 92350, USA.
authors.forename: La Shawnta
authors.initials: LS
authors.lastname: Bell
authors.forename: Terry L
authors.initials: TL
authors.lastname: Butler
authors.forename: R Patti
authors.initials: RP
authors.lastname: Herring
authors.forename: Antonette K
authors.initials: AK
authors.lastname: Yancey
authors.forename: Gary E
authors.initials: GE
authors.lastname: Fraser
mesh_terms: D001741:Black or African American; D006306:Health Surveys; D006801:Humans; D018579:Patient Selection; D016012:Poisson Distribution; D033303:Protestantism; D011795:Surveys and Questionnaires; D013689:Telephone