Centre for Mathematical Modelling of Infectious Diseases, London School of Hygiene & Tropical Medicine, London, UK.
Cell Biology of Infection Laboratory, The Francis Crick Institute; Division of Medicine, UCL, London, UK.
BMC Med. 2021 Apr 27;19(1):106. doi: 10.1186/s12916-021-01982-x.
Routine asymptomatic testing using RT-PCR of people who interact with vulnerable populations, such as medical staff in hospitals or care workers in care homes, has been employed to help prevent outbreaks among vulnerable populations. Although the peak sensitivity of RT-PCR can be high, the probability of detecting an infection will vary throughout the course of an infection. The effectiveness of routine asymptomatic testing will therefore depend on testing frequency and how PCR detection varies over time.
We fitted a Bayesian statistical model to a dataset of twice weekly PCR tests of UK healthcare workers performed by self-administered nasopharyngeal swab, regardless of symptoms. We jointly estimated times of infection and the probability of a positive PCR test over time following infection; we then compared asymptomatic testing strategies by calculating the probability that a symptomatic infection is detected before symptom onset and the probability that an asymptomatic infection is detected within 7 days of infection.
We estimated that the probability that the PCR test detected infection peaked at 77% (54-88%) 4 days after infection, decreasing to 50% (38-65%) by 10 days after infection. Our results suggest a substantially higher probability of detecting infections 1-3 days after infection than previously published estimates. We estimated that testing every other day would detect 57% (33-76%) of symptomatic cases prior to onset and 94% (75-99%) of asymptomatic cases within 7 days if test results were returned within a day.
Our results suggest that routine asymptomatic testing can enable detection of a high proportion of infected individuals early in their infection, provided that the testing is frequent and the time from testing to notification of results is sufficiently fast.
对与弱势群体（如医院的医务人员或养老院的护理人员）接触的人群进行常规无症状 RT-PCR 检测，以帮助预防弱势群体中爆发疫情，这一方法已被采用。尽管 RT-PCR 的峰值灵敏度可能很高，但在感染过程中检测到感染的概率会有所不同。因此，常规无症状检测的效果将取决于检测频率以及 PCR 检测随时间的变化。
我们使用贝叶斯统计模型拟合了一组英国医务人员每周两次的自我管理鼻咽拭子 RT-PCR 检测数据集，无论症状如何。我们共同估计了感染时间以及感染后随时间推移 PCR 检测呈阳性的概率；然后通过计算在症状出现前检测到有症状感染的概率和在感染后 7 天内检测到无症状感染的概率，来比较无症状检测策略。
我们估计 PCR 检测检测到感染的概率在感染后 4 天达到峰值 77%（54-88%），到感染后 10 天降至 50%（38-65%）。我们的结果表明，在感染后 1-3 天检测到感染的概率大大高于先前发表的估计。我们估计，如果在一天内返回检测结果，那么每隔一天进行一次检测，将在症状出现前检测到 57%（33-76%）的有症状病例，以及在 7 天内检测到 94%（75-99%）的无症状病例。
我们的结果表明，只要检测频繁且从检测到通知检测结果的时间足够快，常规的无症状检测可以在感染早期检测到很大比例的感染个体。
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