Department of Public Health and Preventative Medicine, Monash University, Melbourne, Victoria, Australia.
Big Data Institute, Li Ka Shing Centre for Health Informatics, University of Oxford, Oxford, United Kingdom.
PLoS Negl Trop Dis. 2018 Oct 11;12(10):e0006531. doi: 10.1371/journal.pntd.0006531. eCollection 2018 Oct.
It is estimated that 190 million individuals are at risk of blindness from trachoma, and that control by mass drug administration (MDA) is reducing this risk in many populations. Programs are monitored using prevalence of follicular trachoma disease (TF) in children. However, as programs progress to low prevalence there are challenges interpreting this indirect measure of infection. PCR and sero-surveillance are being considered as complementary tools to monitor low-level transmission, but there are questions on how they can be most effectively used. We use a previously-published, mathematical model to explore the dynamic relationship between TF and PCR throughout a control program and a sero-catalytic model to evaluate the utility of two cross-sectional sero-surveys for estimating sero-conversion rates. The simulations show that whilst PCR is more sensitive than TF at detecting infection, the probability of detecting at least one positive individual declines during an MDA program more quickly for PCR than for TF (for the same sample size). Towards the end of a program there is a moderate chance of a random sample showing both low PCR prevalence and higher TF prevalence, which may contribute to the lack of correlation observed in epidemiological studies. We also show that conducting two cross-sectional sero-surveys 10 years apart can provide more precise and accurate estimation of epidemiological parameters than a single survey, supporting previous findings that whilst serology holds great promise, multiple cross-sections from the same community are needed to generate the most valuable information about transmission. These results highlight that the quantitative dynamics of infection and disease should be included alongside the many logistical and practical factors to be considered in designing a monitoring and evaluation strategy at the operational research level, in order to help subsequently inform data collection for individual country programs. Whilst our simulations provide some insight, they also highlight that some level of longitudinal, individual-level data on reinfection and disease may be needed to monitor elimination progress.
据估计，有 1.9 亿人面临沙眼致盲的风险，大规模药物治疗（MDA）正在降低许多人群的这种风险。该计划通过儿童滤泡性沙眼疾病（TF）的患病率进行监测。然而，随着计划进展到低患病率，解释这种感染的间接衡量标准具有挑战性。聚合酶链反应（PCR）和血清监测被认为是监测低水平传播的补充工具，但对于如何最有效地使用它们存在疑问。我们使用之前发表的数学模型来探索控制计划中 TF 和 PCR 之间的动态关系，并使用血清催化模型来评估两项横断面血清调查估计血清转化率的效用。模拟结果表明，虽然 PCR 在检测感染方面比 TF 更敏感，但在 MDA 计划中，PCR 检测至少一个阳性个体的概率比 TF 更快下降（对于相同的样本量）。在计划结束时，随机样本显示低 PCR 流行率和较高 TF 流行率的可能性适中，这可能导致流行病学研究中观察到的缺乏相关性。我们还表明，进行两次相隔 10 年的横断面血清调查比单次调查更能提供更准确和准确的流行病学参数估计，支持以前的研究结果，即虽然血清学具有很大的前景，但需要从同一社区获得多个横断面才能提供关于传播的最有价值的信息。这些结果表明，在设计操作研究层面的监测和评估策略时，应将感染和疾病的定量动态与许多后勤和实际因素一起考虑，以帮助随后为个别国家方案提供数据收集。虽然我们的模拟提供了一些见解，但它们也强调，可能需要一定程度的关于再感染和疾病的纵向、个体水平数据来监测消除进展。
