International Journal of Epidemiology, Vol 26, 1107-1114, Copyright © 1997 by International Epidemiological Association
G Brancato, P Pezzotti, E Rapiti, CA Perucci, D Abeni, A Babbalacchio and G Rezza
BACKGROUND: CD4+ T-lymphocyte (CD4) and platelet counts are good predictors
of the 'maturity' of HIV infection and can be used to impute the date of
infection/seroconversion in individuals for whom this date is unknown.
METHODS: Data from the Italian Seroconversion Study were used to develop a
Weibull regression model for time since seroconversion as a function of the
haematologic markers. The model was used to impute time since HIV
infection/seroconversion in individuals from a prevalent cohort, recruited
through the Lazio regional HIV surveillance system. RESULTS: The range of
the imputed calendar times of infection/seroconversion in 2599 HIV
prevalent individuals was 1972- 1992; the earliest seroconversions occurred
among injecting drug users (IDU). The peak of incidence was reached in 1986
with 340 seroconversions. Among males, the estimated median time from
seroconversion to HIV diagnosis was shorter in IDU (30 months) as compared
to non-IDU (36 months). This difference was smaller for females (26.6
versus 28.4 in IDU and non-IDU, respectively). CONCLUSIONS: This method
permits the estimation of population-based curves of HIV incidence, using
data from surveillance. The results support the hypotheses of an early
spread of the epidemic among IDU in the Lazio region, and of shorter lead
times in this population.
ARTICLES
Multiple imputation method for estimating incidence of HIV infection. The Multicenter Prospective HIV Study
Department of Epidemiology, Lazio Region Health Authority, Rome, Italy.
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