title: Informed consent affects prevalence estimates in an epidemiological study on chronic pruritus: lessons learned from a pretest.
abstract: OBJECTIVE
  It was the purpose of this study to compare prevalence estimates of chronic pruritus as obtained from two population-based samples, one being asked and one not being asked to provide written informed consent.
  
  
  METHODS
  A validated questionnaire measuring the prevalence of chronic itch was sent to two samples (N=51 and N=52) from the general population; one sample was asked to complete and send back an informed consent form and one sample was not.
  
  
  RESULTS
  There were few demographic differences between the two groups. The response rate was slightly higher in those who were not asked to complete an informed consent form. Point, 12-month, and lifetime prevalence estimates in those persons who had not received a consent form, but who had written back were consistently lower (lifetime prevalence: 16% vs. 60%, p=0.01).
  
  
  CONCLUSIONS
  If informed consent is requested, there seems to be a relationship between the presence of chronic pruritus and the willingness to participate in a cohort study. People suffering from chronic pruritus tend to return the questionnaire with the informed consent form more readily. Measures need to be taken to ensure that the response is sufficiently high among participants without the target characteristic in epidemiological studies on chronic symptoms.
authors.affiliation: Department of Clinical Social Medicine, University Hospital Heidelberg, University of Heidelberg, Germany. christian.apfelbacher@med.uni-heidelberg.de
authors.forename: Christian J
authors.initials: CJ
authors.lastname: Apfelbacher
authors.forename: Adrian
authors.initials: A
authors.lastname: Loerbroks
authors.forename: Uwe
authors.initials: U
authors.lastname: Matterne
authors.forename: Tamara
authors.initials: T
authors.lastname: Strassner
authors.forename: Marion
authors.initials: M
authors.lastname: Büttner
authors.forename: Elke
authors.initials: E
authors.lastname: Weisshaar
mesh_terms: D016009:Chi-Square Distribution; D005858:Germany / Q000453:epidemiology; D006801:Humans; D007258:Informed Consent; D008297:Male; D015995:Prevalence; D011537:Pruritus / Q000453:epidemiology*; D011795:Surveys and Questionnaires