title: Who does not participate in a follow-up postal study? a survey of infertile couples treated by in vitro fertilization.
abstract: BACKGROUND
  A good response rate has been considered as a proof of a study's quality. Decreasing participation and its potential impact on the internal validity of the study are of growing interest. Our objective was to assess factors associated with contact and response to a postal survey in a epidemiological study of the long-term outcome of IVF couples.
  
  
  METHODS
  The DAIFI study is a retrospective cohort including 6,507 couples who began an IVF program in 2000-2002 in one of the eight participating French IVF centers. Medical data on all 6,507 couples were obtained from IVF center databases, and information on long-term outcome was available only for participants in the postal survey (n = 2,321). Logistic regressions were used to assess firstly factors associated with contact and secondly factors associated with response to the postal questionnaire among contacted couples.
  
  
  RESULTS
  Sixty-two percent of the 6,507 couples were contacted and 58% of these responded to the postal questionnaire. Contacted couples were more likely to have had a child during IVF treatment than non-contactable couples, and the same was true of respondents compared with non-respondents. Demographic and medical characteristics were both associated with probability of contact and probability of response. After adjustment, having a live birth during IVF treatment remained associated with both probabilities, and more strongly with probability of response. Having a child during IVF treatment was a major factor impacting on participation rate.
  
  
  CONCLUSIONS
  Non-response as well as non-contact were linked to the outcome of interest, i.e. long-term parenthood success of infertile couples. Our study illustrates that an a priori hypothesis may be too simplistic and may underestimate potential bias. In the context of growing use of analytical methods that take attrition into account (such as multiple imputation), we need to better understand the mechanisms that underlie attrition in order to choose the most appropriate method.
authors: INED, 133 boulevard Davout, 75940, Paris Cedex 20, France. penelope.troude@inserm.fr
authors: Penelope
authors: P
authors: Troude
authors: Estelle
authors: E
authors: Bailly
authors: Juliette
authors: J
authors: Guibert
authors: Jean
authors: J
authors: Bouyer
authors: Elise
authors: E
authors: de La Rochebrochard
mesh_terms: D022126:Access to Information; D000328:Adult; D000368:Aged; D001416:Back Pain / Q000523:psychology* / Q000628:therapy; D005260:Female; D006297:Health Services Accessibility; D006305:Health Status Indicators; D006801:Humans; D008297:Male; D008875:Middle Aged; D012423:Rural Health / Q000592:standards*; D012648:Self Care; D012959:Socioeconomic Factors; D014904:Western Australia