Gregson S, Machekano R, Donnelly C A, Mbizvo M T, Anderson R M, Katzenstein D A
Wellcome Trust Centre for the Epidemiology of Infectious Disease, Zoology Department, Oxford University, UK.
AIDS. 1998 Oct 22;12(15):2049-58. doi: 10.1097/00002030-199815000-00017.
To compare HIV incidence estimates from cross-sectional age-specific prevalence data with concurrent cohort estimates and to examine the sensitivity of the estimates to changes in age-categorization and survivorship assumptions.
Two previously described methods of estimating HIV incidence from cross-sectional prevalence data - the cumulative incidence and survival (CIS) and constant prevalence (CP) methods - are applied using data from a study of male factory workers in Harare, Zimbabwe. The methods are applied under two alternative groupings of the HIV prevalence data and under alternative survivorship assumptions: (a) Weibull distribution providing the best fit to the HIV prevalence data using the CIS method; (b) Weibull distribution matching data from an HIV natural history cohort study in Uganda; and (c) survivorship pattern as in (b) with survival periods reducing with increasing age at infection. Age-specific, age-standardized and cumulative HIV incidence estimates are calculated. The results are compared with concurrent longitudinal estimates from 3 years of follow-up of the Harare cohort (1993-1995).
Age-standardized HIV incidence was estimated at 2.02 per 100 man years (95% CI, 1.57-2.47) in the cohort study. There was evidence of recent variability in HIV incidence in these data. Estimates from the cross-sectional methods ranged from 1.98 to 2.74 per 100 man years and were sensitive to changes in age-categorization of the HIV prevalence data and changes in survivorship assumptions. The cross-sectional estimates were higher at central ages and lower at older ages than the cohort estimates. The age-specific estimates from the CIS method were less sensitive to changes in age grouping than those from the CP method.
HIV incidence remains high in Harare. Incidence estimates broadly consistent with cohort estimates can be obtained from single-round cross-sectional HIV prevalence data in established epidemics - even when the underlying assumption of stable endemic prevalence is not fully met. Estimates based on cross-sectional surveys should therefore be explored when reliable longitudinal estimates cannot be obtained. More data on post-HIV infection survivorship distributions in sub-Saharan Africa would facilitate the improvement of estimates of incidence based on cross-sectional surveys.
比较基于横断面特定年龄患病率数据得出的HIV发病率估计值与同期队列研究得出的估计值，并检验这些估计值对年龄分类和生存假设变化的敏感性。
使用来自津巴布韦哈拉雷男性工厂工人研究的数据，应用两种先前描述的从横断面患病率数据估计HIV发病率的方法——累积发病率和生存（CIS）法以及恒定患病率（CP）法。这些方法在HIV患病率数据的两种替代分组以及替代生存假设下应用：（a）使用CIS法时，威布尔分布最能拟合HIV患病率数据；（b）威布尔分布与乌干达一项HIV自然史队列研究的数据匹配；（c）与（b）相同的生存模式，但感染时年龄越大生存期越短。计算特定年龄、年龄标准化和累积HIV发病率估计值。将结果与哈拉雷队列3年随访（1993 - 1995年）的同期纵向估计值进行比较。
队列研究中年龄标准化HIV发病率估计为每100人年2.02例（95%可信区间，1.57 - 2.47）。这些数据中有证据表明HIV发病率近期存在变异性。横断面方法得出的估计值范围为每100人年1.98至2.74例，并且对HIV患病率数据的年龄分类变化和生存假设变化敏感。横断面估计值在中年时高于队列估计值，在老年时低于队列估计值。CIS法得出的特定年龄估计值比CP法对年龄分组变化的敏感性更低。
哈拉雷的HIV发病率仍然很高。在已确立的疫情中，即使稳定地方流行患病率的基本假设未完全满足，也可从单轮横断面HIV患病率数据中获得与队列估计值大致一致的发病率估计值。因此，当无法获得可靠的纵向估计值时，应探索基于横断面调查的估计值。撒哈拉以南非洲更多关于HIV感染后生存分布的数据将有助于改进基于横断面调查的发病率估计。
