Muñoz A, Xu J
Department of Epidemiology, Johns Hopkins School of Public Health, Baltimore, MD 21205, USA.
Stat Med. 1996;15(21-22):2459-73. doi: 10.1002/(sici)1097-0258(19961130)15:22<2459::aid-sim464>3.0.co;2-q.
The objective of the methods proposed is to provide a parametric model for the incubation of AIDS and to use the chosen parameterization to test for the effect of age at seroconversion, and, after adjusting for markers of immunosuppression, to assess variations in periods corresponding to different levels of use of AIDS therapies at the population level. We compared the fit of Weibull, log-normal and three-parameter logistic models incorporating truncation in prevalent cohort and interval censored data. We showed the advantages by restricting the analysis to follow-up durations of greater than five years to improve estimation of the tail of the distribution for the prediction of long-term survivors. We applied the proposed methods to the combination of 1649 seroprevalent and 476 seroconverters with 1022 and 177 AIDS cases, respectively, who have been followed in the Multicenter AIDS Cohort Study (MACS) up to April 1995. Differences according to age at seroconversion are quantified in terms of relative percentiles and their associated 95 per cent confidence intervals were calculated using methods of multiple imputation. Using the proposed methods, we found that the log-normal model provides a fit as good as the three-parameter logistic; both are close to the non-parametric estimate and are significantly better than the fit of the Weibull model. We found that the older the age at seroconversion, the shorter the time to AIDS (relative percentile = 0.72 for age > or = 40 versus age < 25), and that the incubation of AIDS in calendar periods where treatment has been widely administered has been significantly longer among individuals with low CD4 cell counts.
所提出方法的目标是为艾滋病潜伏期提供一个参数模型，并使用选定的参数化方法来检验血清转化时年龄的影响，并且在对免疫抑制标志物进行调整之后，评估在人群水平上与不同程度艾滋病治疗使用情况相对应的时间段的变化。我们比较了威布尔模型、对数正态模型以及在现患队列和区间删失数据中纳入截断的三参数逻辑斯蒂模型的拟合情况。我们通过将分析限制在大于五年的随访期来展示其优势，以改善对分布尾部的估计从而预测长期存活者。我们将所提出的方法应用于1649名血清阳性者和476名血清转化者的组合数据，他们分别有1022例和177例艾滋病病例，这些数据来自多中心艾滋病队列研究（MACS），随访至1995年4月。根据血清转化时的年龄差异以相对百分位数进行量化，并使用多重填补方法计算其相关的95%置信区间。使用所提出的方法，我们发现对数正态模型的拟合效果与三参数逻辑斯蒂模型一样好；两者都接近非参数估计，并且显著优于威布尔模型的拟合。我们发现血清转化时年龄越大，患艾滋病的时间越短（年龄≥40岁与年龄＜25岁相比，相对百分位数 = 0.72），并且在CD4细胞计数低的个体中，在广泛进行治疗的日历时间段内艾滋病潜伏期显著更长。
