Perspectives on Using Backcalculation to Estimate HIV Prevalence and Project AIDS Incidence

  • Mitchell H. Gail
  • Philip S. Rosenberg

Abstract

The method of backcalculation uses information on the AIDS incubation distribution to estimate the previous rates of HIV infection (the “infection curve”) needed to account for the observed AIDS incidence series. Projections of future AIDS incidence are then obtained by distributing estimates of the numbers of previously infected people forward using the incubation distribution. We review the major sources of uncertainty for backcalculation procedures that were applicable to AIDS incidence data through mid-1987 and discuss estimates of cumulative HIV infections based on such data.

Beginning in mid-1987, projections of AIDS incidence derived from backcalculation exceeded observed AIDS counts in exposure groups with good access to zidovudine (AZT) (Gail, Rosenberg and Goedert, 1990; Rosenberg et al, 1991b). Such treatment can cause secular changes in the incubation distribution, and failure to take treatment into account can lead to sharp reductions in backcalculated estimates of cumulative HIV infections. The Stage model of Brookmeyer (1991) takes treatment into account, as does the “timesince-infection” (TSI) model of Rosenberg, Gail and Carroll (1991). The TSI model also allows for the broadened surveillance definition of AIDS that was adopted in 1987. Both models estimate a decreasing trend in the rate of HIV infection in the United States since the mid-1980s. Both models yield estimates of cumulative HIV infections through 1990 that are broadly consistent with estimates obtained by simpler backcalculation models applied to AIDS incidence data through mid-1987. However, estimates of numbers infected and projections of AIDS incidence are higher for the Stage model than for the TSI model, mainly because the parameters used with the Stage model imply that more treatment was in use and that treatment was more efficacious than in the TSI model. Both models predict continued high levels of AIDS incidence through 1994.

Keywords

Human Immunodeficiency Virus Infection Acquire Immune Deficiency Syndrome Stage Model Plausible Range Multicenter AIDS Cohort Study 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer Science+Business Media New York 1992

Authors and Affiliations

  • Mitchell H. Gail
    • 1
  • Philip S. Rosenberg
    • 1
  1. 1.Epidemiologic Methods SectionNational Cancer InstituteRockvilleUSA

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