Porter K; International Conference on AIDS.
Int Conf AIDS. 2000 Jul 9-14; 13: abstract no. TuOrC369.
K. Porter, MRC Clinical Trials Unit, 222 Euston Road, London NW1 2DA, United Kingdom, Tel.: +44 20 767 047 15, Fax: +44 20 767 048 15, E-mail: k.porter@ctu.mrc.ac.uk
Objective: to compare estimates of changes in HIV survival over time derived from seroconverter and prevalent cohorts. Design/ Methods: using CASCADE pooled data from seroconverter cohorts, we examined the relative risk of death from HIV seroconversion by calendar time at risk from 1 January 1991. We repeated the analyses, ignoring knowledge of the time of seroconversion, but adjusting for the CD4 cell count at the time the participant came under observation, thus mimicking a prevalent cohort. We compared the estimates from the `prevalent' cohort approach to those obtained from the seroconverter cohort. Results: Of 5428 subjects at risk on 1 January 1991 or later, 1312 (24.2%) had died. In the analysis based on time from seroconversion, estimates of the effect of calendar year showed marked reductions in mortality in 1997-99 only, with no evidence of a linear trend over the period 1991 to 1996 (p-trend = 0.85). Using the prevalent cohort approach we observed a decrease in the relative risk of death from 1991 to 1998-99, with a statistically significant trend of a decrease in risk from 1991 to 1996 (p-trend = 0.002). Similar findings were observed when we repeated the analyses taking the start date of the cohort as 1 January 1988. Conclusion: The adjustment for duration of infection in prevalent cohorts through laboratory markers may be inadequate and can give misleading survival estimates. Lack of knowledge of HIV infection duration may lead to biased and exaggerated estimates of survival improvements over time.
Publication Types:
Keywords:
- Acquired Immunodeficiency Syndrome
- Bias (Epidemiology)
- CD4 Lymphocyte Count
- HIV Infections
- HIV Seropositivity
- Humans
- Knowledge
- Population Groups
- Survival
- Time
- mortality
Other ID:
UI: 102239229
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