Document 2317
 DOCN  M94A2317
 TI    Influence of therapy on HIV incidence estimates in Italy.
 DT    9412
 AU    Mariotti S; Cascioli R; Istituto Superiore di Sanita, Rome, Italy.
 SO    Int Conf AIDS. 1994 Aug 7-12;10(1):331 (abstract no. PC0257). Unique
       Identifier : AIDSLINE ICA10/94370258
 AB    OBJECTIVE. A back-calculation method relying on a non-stationary
       incubation period is used to reconstruct HIV incidence from observed
       AIDS cases. Under several hypotheses for the effect of treatment in
       modifying the incubation period, the numbers of estimated HIV infections
       in Italy are evaluated. METHODS. The method implemented here is a
       modification of the two infection stages model proposed originally by
       Brookmeyer and Liao, with inclusion of limited length of time in which
       therapy is effective. The effect of therapy on estimated HIV infection
       is investigated for the first time in a sistematic way, along different
       dimensions. Two different estimated progressions for the percentage of
       ARC subjects in treatment in different calendar years (Italian vs. USA
       estimate), two different values for the effectiveness of the treatment
       in reducing the risk (RR reduced to 0.5 vs 0.33), and three different
       lengths for the period in which therapy is effective (2 years, 4 yrs,
       unlimited), are considered in the simulations. RESULTS. Using data up to
       March 1993, cumulative estimated infections at the end of 1991 and
       quarterly incidence corresponding to estimated peak of infection are
       shown in the Table for each combination of parameters and no therapy. An
       estimate with a slower progression of treatment diffusion (USA), smaller
       reduction of the risk (0.5), and therapy effective only for two years
       yields a cumulative infection estimate of 65,400 as compared to 93,300
       for extreme values of the parameters in the opposite direction.
       CONCLUSIONS. All factors influencing therapy were shown to have an
       important effect in the estimate of HIV incidence. Not taking into
       account these factors might severely bias the estimates. TABULAR DATA,
       SEE ABSTRACT VOLUME.
 DE    Acquired Immunodeficiency Syndrome/DRUG THERAPY/*EPIDEMIOLOGY  Antiviral
       Agents/*THERAPEUTIC USE  Comparative Study  Cross-Sectional Studies
       Human  HIV Infections/DRUG THERAPY/*EPIDEMIOLOGY  Incidence
       Italy/EPIDEMIOLOGY  Models, Statistical  Treatment Outcome  United
       States/EPIDEMIOLOGY  MEETING ABSTRACT

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