en
Scientific article
English

A joint back calculation model for the imputation of the date of HIV infection in a prevalent cohort

Published inStatistics in medicine, vol. 27, no. 23, p. 4835-4853
Publication date2008
Abstract

In studies of the natural history of HIV-1 infection, the time scale of primary interest is the time since infection. Unfortunately, this time is very often unknown for HIV infection and using the follow-up time instead of the time since infection is likely to provide biased results because of onset confounding. Laboratory markers such as the CD4 T-cell count carry important information concerning disease progression and can be used to predict the unknown date of infection. Previous work on this topic has made use of only one CD4 measurement or based the imputation on incident patients only. However, because of considerable intrinsic variability in CD4 levels and because incident cases are different from prevalent cases, back calculation based on only one CD4 determination per person or on characteristics of the incident sub-cohort may provide unreliable results. Therefore, we propose a methodology based on the repeated individual CD4 T-cells marker measurements that use both incident and prevalent cases to impute the unknown date of infection. Our approach uses joint modelling of the time since infection, the CD4 time path and the drop-out process. This methodology has been applied to estimate the CD4 slope and impute the unknown date of infection in HIV patients from the Swiss HIV Cohort Study. A procedure based on the comparison of different slope estimates is proposed to assess the goodness of fit of the imputation. Results of simulation studies indicated that the imputation procedure worked well, despite the intrinsic high volatility of the CD4 marker.

Keywords
  • Adult
  • Algorithms
  • Biological Markers
  • CD4 Lymphocyte Count/*methods
  • CD4-Positive T-Lymphocytes/immunology
  • Cohort Studies
  • Cross-Sectional Studies
  • HIV Infections/*transmission
  • HIV Seroprevalence
  • *Hiv-1
  • Humans
  • *Models, Statistical
  • Switzerland/epidemiology
  • Time Factors
Affiliation Not a UNIGE publication
Citation (ISO format)
TAFFE, Patrick, MAY, Margaret. A joint back calculation model for the imputation of the date of HIV infection in a prevalent cohort. In: Statistics in medicine, 2008, vol. 27, n° 23, p. 4835–4853. doi: 10.1002/sim.3294
Main files (1)
Article
accessLevelRestricted
Identifiers
ISSN of the journal0277-6715
534views
0downloads

Technical informations

Creation2012/03/27 09:24:02
First validation2012/03/27 09:24:02
Update time2023/03/14 17:21:22
Status update2023/03/14 17:21:22
Last indexation2024/02/12 19:52:32
All rights reserved by Archive ouverte UNIGE and the University of GenevaunigeBlack