title: [Impact of delayed diagnoses bias on the estimation of AIDS incubation].
abstract: OBJECTIVE
  Using the HIV positive paid blood donors (PBDs) as example, to investigate the impact of the delayed diagnosed HIV/AIDS patients on the calculated median incubation of AIDS.
  
  
  METHODS
  Information was retrospectively collected on HIV/AIDS patients who were infected through paid blood donation. Data was from the national HIV/AIDS case reporting system. The time of diagnosed HIV/AIDS after the screening was defined as delayed diagnoses. All the cases were diagnosed between Jan. 1(st) 1995 and the end of the screening were classified as group 1, while the cases diagnosed between Jan. 1(st) 1995 and Dec. 31(st) 2010 were classified as group 2. Kaplan-Meier method was used to calculate the median AIDS incubation of cases from the two groups. Results from the two groups on their incubation periods were compared.
  
  
  RESULTS
  From the data of group 1, we noticed that the median AIDS incubation was 9.62 years but the 95%CI were not provided in the results of SAS software. When using the data from group 2, we found that the median AIDS incubation was 9.83 years, with the 95%CI as 9.73 to 9.83 years.
  
  
  CONCLUSIONS
  Our data showed that, if excluding the delayed diagnosed cases, the AIDS incubation periods were shorter and biased.
authors.affiliation: National Center for AIDS/STD Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing 102206, China; School of Public Health, Peking Union Medical College.
authors.forename: Hui-xin
authors.initials: HX
authors.lastname: Liu
authors.forename: Lu
authors.initials: L
authors.lastname: Wang
authors.forename: Qian-qian
authors.initials: QQ
authors.lastname: Qin
authors.forename: Zheng-wei
authors.initials: ZW
authors.lastname: Ding
authors.forename: Ning
authors.initials: N
authors.lastname: Wang
mesh_terms: D000163:Acquired Immunodeficiency Syndrome / Q000175:diagnosis* / Q000821:virology*; D000328:Adult; D015982:Bias; D001782:Blood Donors; D057210:Delayed Diagnosis; D005260:Female; D015497:HIV-1 / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D017735:Virus Latency