title: Lack of consistency between five definitions of nonprogression in cohorts of HIV-infected seroconverters.
abstract: OBJECTIVE
  To identify appropriate criteria for characterizing HIV-infected nonprogressors.
  
  
  METHODS
  Five definitions were compared as follows: (1) last CD4 count > 500 x 10(6)/l; (2) two most recent CD4 counts > 500 x 10(6)/l; (3) calculated CD4 count based on linear regression > 500 x 10(6)/l; (4) CD4 slope > or = 0 with no antiretroviral use; (5) all CD4 counts > 500 x 10(6)/l, decline in CD4 slope < 5 cells per year, no antiretroviral use.
  
  
  METHODS
  Five prospective cohorts of homosexual men with documented dates of HIV-1 seroconversion.
  
  
  METHODS
  Proportions of nonprogressors were calculated 7, 8, 9 and 10 years following seroconversion (n = 285). Definitions were evaluated with respect to consistency over time and across sites. Subjects lacking CD4 counts within 3 years preceding end of follow-up were excluded.
  
  
  RESULTS
  Across sites, proportions of nonprogressors ranged from 1% (definition 5) to 17.5% (definition 1) 10 years after seroconversion. Definitions based on absolute CD4 counts (definitions 1-3) had higher proportions and were less consistent than those based on stable slopes (definitions 4 and 5). For each definition, proportions decreased as follow-up increased, but were most stable for definition 4 (3%). Site differences decreased as follow-up increased, but remained nearly threefold for definitions 1-3. None of the definitions classified the same subjects as nonprogressors at any timepoint.
  
  
  CONCLUSIONS
  Observations regarding nonprogression are highly dependent on the definition and the duration of follow-up. Our findings highlight methodological challenges which will need to be overcome in natural history studies of nonprogression.
authors.affiliation: Department of Health Care and Epidemiology, University of British Columbia, St Paul's Hospital, Vancouver, Canada.
authors.forename: S A
authors.initials: SA
authors.lastname: Strathdee
authors.forename: P J
authors.initials: PJ
authors.lastname: Veugelers
authors.forename: K A
authors.initials: KA
authors.lastname: Page-Shafer
authors.forename: A
authors.initials: A
authors.lastname: McNulty
authors.forename: A R
authors.initials: AR
authors.lastname: Moss
authors.forename: M T
authors.initials: MT
authors.lastname: Schechter
authors.forename: G J
authors.initials: GJ
authors.lastname: van Griensven
authors.forename: R A
authors.initials: RA
authors.lastname: Coutinho
mesh_terms: D015496:CD4-Positive T-Lymphocytes / Q000473:pathology*; D015331:Cohort Studies; D015658:HIV Infections / Q000473:pathology / Q000503:physiopathology*; D018451:Homosexuality, Male; D006801:Humans; D018655:Lymphocyte Count; D008297:Male; D011379:Prognosis