Dietz K, Seydel J, Schwartländer B
Department of Medical Biometry, Eberhard-Karls-University, Tübingen, Germany.
Stat Med. 1994;13(19-20):1991-2008. doi: 10.1002/sim.4780131910.
The paper presents an application of back-projection methods to the reported AIDS data which are collected by the AIDS Center in the Federal Office of Health, Berlin. The analysis is based on all data reported up to 31 December 1992. The data are broken down by major risk groups. Correction for reporting delays takes into account temporal changes in their distribution. The paper applies the EMS algorithm for the estimation of HIV incidence. The incubation period is modelled according to a convolution of several exponential distributions which describe time dependent phenomena like change of case definition and therapy effects. For each case it is reported whether an antibody test has been performed before diagnosis, and if yes, at what time this test was performed. The modelling of the incubation distribution takes into account the transition from a state 'not yet tested' into a state 'tested'. Only tested individuals in three pre-AIDS states are eligible for treatment. The model allows us to estimate not only the current total HIV prevalence but also a breakdown into those that are not yet tested, those that are tested but not yet treated and those that are under treatment. The results depend on the assumptions about the effect of treatment and on the degree of smoothing applied in the EMS algorithm.
本文介绍了反投影方法在德国联邦卫生部艾滋病中心收集的艾滋病报告数据中的应用。分析基于截至1992年12月31日报告的所有数据。数据按主要风险群体进行了分类。报告延迟校正考虑了其分布的时间变化。本文应用EMS算法估计HIV发病率。潜伏期根据几种指数分布的卷积进行建模，这些指数分布描述了随时间变化的现象，如病例定义的变化和治疗效果。对于每个病例，报告了在诊断前是否进行了抗体检测，如果进行了检测，检测是在何时进行的。潜伏期分布的建模考虑了从“未检测”状态到“已检测”状态的转变。只有处于三种艾滋病前期状态且已检测的个体才有资格接受治疗。该模型不仅使我们能够估计当前HIV的总体流行率，还能将其细分为未检测者、已检测但未治疗者和正在接受治疗者。结果取决于对治疗效果的假设以及EMS算法中应用的平滑程度。
