title: Retrospective validation of a surveillance system for unexplained illness and death: New Haven County, Connecticut.
abstract: OBJECTIVE
  This study investigated retrospective validation of a prospective surveillance system for unexplained illness and death due to possibly infectious causes.
  
  
  METHODS
  A computerized search of hospital discharge data identified patients with potential unexplained illness and death due to possibly infectious causes. Medical records for such patients were reviewed for satisfaction of study criteria. Cases identified retrospectively were combined with prospectively identified cases to form a reference population against which sensitivity could be measured.
  
  
  RESULTS
  Retrospective validation was 41% sensitive, whereas prospective surveillance was 73% sensitive. The annual incidence of unexplained illness and death due to possibly infectious causes during 1995 and 1996 in the study county was conservatively estimated to range from 2.7 to 6.2 per 100,000 residents aged 1 to 49 years.
  
  
  CONCLUSIONS
  Active prospective surveillance for unexplained illness and death due to possibly infectious causes is more sensitive than retrospective surveillance conducted through a published list of indicator codes. However, retrospective surveillance can be a feasible and much less labor-intensive alternative to active prospective surveillance when the latter is not possible or desired.
authors.affiliation: Connecticut Emerging Infections Program, Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, Conn., USA.
authors.forename: M D
authors.initials: MD
authors.lastname: Kluger
authors.forename: A N
authors.initials: AN
authors.lastname: Sofair
authors.forename: C J
authors.initials: CJ
authors.lastname: Heye
authors.forename: J I
authors.initials: JI
authors.lastname: Meek
authors.forename: R K
authors.initials: RK
authors.lastname: Sodhi
authors.forename: J L
authors.initials: JL
authors.lastname: Hadler
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D003141:Communicable Diseases / Q000453:epidemiology* / Q000401:mortality; D003237:Connecticut / Q000453:epidemiology; D016638:Critical Illness / Q000145:classification* / Q000401:mortality; D006801:Humans; D015994:Incidence; D007223:Infant; D007362:Intensive Care Units / Q000706:statistics & numerical data; D008875:Middle Aged; D010351:Patient Discharge; D011159:Population Surveillance / Q000379:methods*; D011446:Prospective Studies; D012189:Retrospective Studies; D012680:Sensitivity and Specificity