title: Validity of family history data on PD: evidence for a family information bias.
abstract: OBJECTIVE
  To study the validity of information provided by case and control subjects (or their proxies) about PD among their first-degree relatives.
  
  
  METHODS
  Secondary cases of PD were assessed both through a single informant (family history method) and through the study of each relative (family study method). The family study method was considered as the standard for comparison, and the sensitivity and specificity of the family history method were studied.
  
  
  RESULTS
  A total of 133 population-based case subjects and their 655 relatives were recruited, and 119 population-based control subjects and their 511 relatives. Sensitivity was 68% (95% CI = 47 to 85) for cases and 45% (95% CI = 17 to 77) for controls. Specificity was 99% (95% CI = 98 to 99) for cases and 100% (95% CI = 99 to 100) for controls. The odds ratio (OR) for family history of PD was 4.34 (95% CI = 1.63 to 11.58, p = 0.003) using the family history method and 1.86 (95% CI = 0.78 to 4.44, p = 0.16) using the family study method. The former significant OR more than doubled the latter not significant OR (relative bias = 133%). Bias was more pronounced for proxy interviews and for women informants, and when the relatives were siblings, were living, and were examined or had medical record documentation.
  
  
  CONCLUSIONS
  Case subjects with PD (or their proxies) are more aware of PD among their first-degree relatives than control subjects (or their proxies); however, they overreport PD in relatives who are not affected. This causes a substantial family information bias.
authors.affiliation: Department of Health Sciences Research, Mayo Clinic and Mayo Foundation, Rochester, MN 55905, USA.
authors.forename: A
authors.initials: A
authors.lastname: Elbaz
authors.forename: S K
authors.initials: SK
authors.lastname: McDonnell
authors.forename: D M
authors.initials: DM
authors.lastname: Maraganore
authors.forename: K J
authors.initials: KJ
authors.lastname: Strain
authors.forename: D J
authors.initials: DJ
authors.lastname: Schaid
authors.forename: J H
authors.initials: JH
authors.lastname: Bower
authors.forename: J E
authors.initials: JE
authors.lastname: Ahlskog
authors.forename: W A
authors.initials: WA
authors.lastname: Rocca
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001364:Awareness; D015982:Bias; D016022:Case-Control Studies; D005192:Family Health; D005260:Female; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000379:methods; D008490:Medical Informatics / Q000592:standards; D008499:Medical Records / Q000706:statistics & numerical data; D008875:Middle Aged; D008910:Minnesota / Q000453:epidemiology; D015588:Observer Variation; D016017:Odds Ratio; D010300:Parkinson Disease / Q000175:diagnosis / Q000453:epidemiology* / Q000235:genetics*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity