HIV infection projections as estimated by non-parametric and semi-parametric models: an application to Italian data.

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HIV infection projections as estimated by non-parametric and semi-parametric models: an application to Italian data.

Int Conf AIDS. 1993 Jun 6-11;9(1):100 (abstract no. WS-C19-3). Unique Identifier : AIDSLINE MED/93333224
Mariotti S; Cascioli R; Istituto Superiore di Sanita, Rome, Italy.

Abstract: OBJECTIVE: to compare two popular models for estimating and projecting HIV infection in a practical application to Italian AIDS data. METHODS: The non-parametric Regression Decomposition RD) model developed at Harvard by Pagano and co-workers is compared to the classical semi-parametric Backcalculation model proposed by Brookmeyer and Liao (Biometrics, 1990), in two different variants--the best fit algorithm for choosing among a number of different step functions (BC-1) and the smoothing algorithm proposed by Becker (BC-2). The AIDS incubation period distribution was derived from an estimate on an Italian cohort Mariotto, Mariotti et al.-AJE 1992). The total number of AIDS cases analyzed is 13770 out of a total of 14,783 at September 30, 1992, excluding diagnoses in the last three months, for which the adjustment for reporting delay--implemented according to the method proposed by Brookmeyer and Liao--is not feasible. RESULTS: The HIV incidence curves for the different models are shown in the figure. This graph is relative to the sum of all subgroups, with no account of the therapy effect on the observed AIDS cases. The overall trends of the incidence is the same for all models, showing a peak in 1986 and a decrease thereafter. No estimates are possible after 1989, because few AIDS cases derive from infections in this period. The total prevalence estimates at the end of 1989 are 51,700, 57,200 and 59,800 respectively for the BC-1, BC-2 and RD methods. The total number of infected subjects separately for IVDU's, homosexuals and other categories heterosexuals, hemophilics, etc.) with Becker method are 38,500, 6,800, and 9,900 respectively. Projections of AIDS cases expected in the next few years are also similar according to the different techniques. CONCLUSION: In spite of the differences between the BC and RD methods, the results seem to agree quite well, especially when comparing RD and the smoothed version of the Backcalculation algorithm BC-2. TABULAR DATA, SEE ABSTRACT VOLUME.

Keywords: *Acquired Immunodeficiency Syndrome/EPIDEMIOLOGY *HIV Infections/EPIDEMIOLOGY *Models, Statistical
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M93B5823

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