title: Loss to follow-up in an international, multicentre observational study.
abstract: OBJECTIVE
  The aim of this work was to assess loss to follow-up (LTFU) in EuroSIDA, an international multicentre observational cohort study.
  
  
  METHODS
  LTFU was defined as no follow-up visit, CD4 cell count measurement or viral load measurement after 1 January 2006. Poisson regression was used to describe factors related to LTFU.
  
  
  RESULTS
  The incidence of LTFU in 12 304 patients was 3.72 per 100 person-years of follow-up [95% confidence interval (CI) 3.58-3.86; 2712 LTFU] and varied among countries from 0.67 to 13.35. After adjustment, older patients, those with higher CD4 cell counts, and those who had started combination antiretroviral therapy all had lower incidences of LTFU, while injecting drug users had a higher incidence of LTFU. Compared with patients from Southern Europe and Argentina, patients from Eastern Europe had over a twofold increased incidence of LTFU after adjustment (incidence rate ratio 2.16; 95% CI 1.84-2.53; P<0.0001). A total of 2743 patients had a period of >1 year with no CD4 cell count or viral load measured during the year; 743 (27.1%) subsequently returned to follow-up.
  
  
  CONCLUSIONS
  Some patients thought to be LTFU may have died, and efforts should be made to ascertain vital status wherever possible. A significant proportion of patients who have a year with no follow-up visit, CD4 cell count measurement or viral load measurement subsequently return to follow-up.
authors.affiliation: Royal Free and University College Medical School, London, UK. a.mocroft@pcps.ucl.ac.uk
authors.forename: A
authors.initials: A
authors.lastname: Mocroft
authors.forename: O
authors.initials: O
authors.lastname: Kirk
authors.forename: P
authors.initials: P
authors.lastname: Aldins
authors.forename: A
authors.initials: A
authors.lastname: Chies
authors.forename: A
authors.initials: A
authors.lastname: Blaxhult
authors.forename: N
authors.initials: N
authors.lastname: Chentsova
authors.forename: N
authors.initials: N
authors.lastname: Vetter
authors.forename: F
authors.initials: F
authors.lastname: Dabis
authors.forename: J
authors.initials: J
authors.lastname: Gatell
authors.forename: J D
authors.initials: JD
authors.lastname: Lundgren
mesh_terms: D000328:Adult; D023241:Antiretroviral Therapy, Highly Active; D018791:CD4 Lymphocyte Count / Q000379:methods; D005060:Europe / Q000453:epidemiology; D005260:Female; D005500:Follow-Up Studies; D015658:HIV Infections / Q000453:epidemiology*; D015497:HIV-1; D006801:Humans; D015994:Incidence; D008297:Male; D012044:Regression Analysis; D019562:Viral Load / Q000379:methods