South African Centre for Epidemiological Modelling and Analysis, Stellenbosch University, Stellenbosch, South Africa.
PLoS One. 2012;7(9):e44377. doi: 10.1371/journal.pone.0044377. Epub 2012 Sep 12.
We derive a new method to estimate the age specific incidence of an infection with a differential mortality, using individual level infection status data from successive surveys. The method consists of a) an SI-type model to express the incidence rate in terms of the prevalence and its derivatives as well as the difference in mortality rate, and b) a maximum likelihood approach to estimate the prevalence and its derivatives. Estimates can in principle be obtained for any chosen age and time, and no particular assumptions are made about the epidemiological or demographic context. This is in contrast with earlier methods for estimating incidence from prevalence data, which work with aggregated data, and the aggregated effect of demographic and epidemiological rates over the time interval between prevalence surveys. Numerical simulation of HIV epidemics, under the presumption of known excess mortality due to infection, shows improved control of bias and variance, compared to previous methods. Our analysis motivates for a) effort to be applied to obtain accurate estimates of excess mortality rates as a function of age and time among HIV infected individuals and b) use of individual level rather than aggregated data in order to estimate HIV incidence rates at times between two prevalence surveys.
我们提出了一种新方法，用于根据连续调查的个体感染状态数据，估计具有差异死亡率的传染病的特定年龄发病率。该方法包括：a）一个 SI 型模型，用流行率及其导数以及死亡率差异来表示发病率；b）最大似然法来估计流行率及其导数。原则上，可以针对任何选定的年龄和时间获得估计值，并且不对流行病学或人口统计学背景做出特殊假设。这与之前从流行率数据估计发病率的方法不同，后者使用聚合数据，以及在两次流行率调查之间的时间间隔内人口统计学和流行病学率的聚合效应。在假定由于感染而导致超额死亡率已知的情况下，对 HIV 流行的数值模拟表明，与之前的方法相比，偏差和方差得到了更好的控制。我们的分析促使：a）努力获得 HIV 感染者中随时间变化的年龄特异性超额死亡率的准确估计值；b）在两次流行率调查之间的时间内，使用个体水平而不是聚合数据来估计 HIV 发病率。
