After one week back from Winter Break—and with new hyper-virulent strains of the COVID-19 virus surfacing—保利预科 continues to be innovative in its approach to keeping our community safe. 在大约一年前转向远程教育之后, 9月，我们迎来了超过1岁的孩子,000名幼儿园至12年级的学生回到我们的两个校区. Keeping our students in school requires constant evaluation and evolution of our safety practices.

在保利预科学校，我们的 健康与安全小组 引导我们解决了数量惊人的问题:有多少学生可以回国? 他们怎么去学校? 我们要不要门测? 哪种测试?? 上课是在室内还是室外? 窗户会开着吗?? 我们需要监控测试吗? 我们将如何供应和吃午餐? 

Schools across the city and globe have demonstrated wide-ranging approaches in tackling these questions. In addition to the outdoor tented classrooms that housed our fall Dyker Heights courses, we implemented one of the most aggressive COVID-19 testing strategies in the country. Our plan included regular polymerase chain reaction-based (PCR) testing of asymptomatic community members; PCR tests are considered the gold standard of testing in accuracy. 理论上，它们在假阳性或假阴性方面几乎是完美无缺的, 它们对于保护机构来说是完美的. 但是什么时候这些“完美的测试”会失败呢?

跌落检测策略:PCR在实践中的应用

在我们最初几个月的PCR测试中, 我们要求在每次延长休息后进行单独的PCR测试, 但每次测试要50到100美元, ramping up our testing frequency was prohibitively expensive: the first PCR hurdle. We addressed this key problem by using a pooled testing strategy on a weekly basis. Pooling individual samples sacrifices some test sensitivity for the ability to test the entire batch at once, 这大大降低了成本. 秋天纽约市的病毒感染率很低, 这些汇集的批次中的大多数结果都是完全负面的. 当一批产生阳性结果时, 我们的测试提供者会进行反射测试, meaning that they would test smaller groups within the positive pool until we identified the specific positive individual.

从九月到十二月, 我们在执行测试协议方面做得更好了, 我们每周继续测试越来越多的群体. On Mondays, we collected saliva samples in the mornings and transported them to our contracted lab. The PCR test itself requires dozens of cycles to be run on each sample in a high-complexity reference laboratory using a molecular testing process called reverse transcription polymerase chain reaction (RT-PCR). This process takes approximately seven hours on the fastest commercially available machines. Hence, we would receive test results approximately one day after collecting samples. 随着COVID-19发病率的上升，整个城市的实验室变得越来越慢, 延迟可能会延长至48小时. 第二个PCR障碍, 延迟的结果, means we would have school for a full day or more after collecting samples and 不 know if we had positives in the community.

数据:了解我们的社区积极因素

根据我们自己的数据, we learned that older students were more likely to test positive than younger students; that staff were more likely to test positive than teaching faculty; and that males were overwhelmingly more likely to test positive than females. 但没有什么教训比我们追踪接触者的教训更有力了, that the true cost of a positive case was 不 limited to the mandatory quarantining of the individual who tested positive. A single student who tested positive would force the quarantine of dozens of others—classmates, 同乘公共汽车的人, 兄弟姐妹, carpods, 老师, 顾问, 午餐监事, 以及任何课外活动.

在策略中加入抗原(快速)测试

With new strains of coronavirus that are estimated to be 50-70% more transmissible than the previous strain, 任何一个案例的存在, 24-48小时内不被发现, 挑战我们保持校园开放的能力. 抗原检测(也称为快速检测)是PCR检测的一种替代方法. 在今年的上半年, 我们使用了少量的抗原测试, 已获得必要的有限实验室执照来管理它们. 抗原检测更便宜, 少麻烦, 快得多, 而且可能不如PCR检测准确.

Dr. 哈佛大学的Michael Mina说.H. 陈公共卫生学院 is a vocal and well-respected proponent of using rapid antigen testing on a regular basis. Antigen tests produce a result in less than 15 minutes and can be administered at a fraction of the cost of a PCR test. 我们的程序是每周用鼻拭子擦拭我们社区的大部分人, 目的是在开学前的周一尽可能多地测试. When their tests are cleared as negative, they are able to participate in school on campus. If they are positive, they will immediately be sampled for a PCR test on or off site. This reduces both the exposure on campus during the school day and the contact tracing burden. 我们每周至少对两个校区的所有成年人进行一次快速测试, 还有两个高中的成绩, 9和10, 谁每隔一周上学.  We will continue to transition away from weekly PCR testing and towards weekly rapid testing for as many students and employees in our population as possible.

PCR检测v. 抗原(快速)试验

PCR检测旨在直接检测病毒的遗传物质，它确实做到了 不 目的是检测传染性. 感染COVID-19的人仅在感染后的一段时间内具有传染性, 这意味着聚合酶链反应检测呈阳性通常不能证实传染性. 感染期大约在感染后两到三天开始, lasts through the remainder of incubation (defined as the period prior to the onset of first symptoms) and usually ends a week later for a total of approximately two weeks or less. 抗原检测常常被误解和误传. Antigen tests are much better indicators of infectiousness than the more technically accurate PCR tests because they detect the presence of viral proteins known as antigens, 这些通常存在于被感染的人实际上具有传染性(或, 至少, 最具传染性时). 迄今为止, antigen tests have often been incorrectly benchmarked against PCR tests throughout all stages of infection—thereby comparing antigen tests to PCR outside of their intended use. 更多的 最近的研究 侧重于整个感染期的比较, 对感染控制而言，哪个时期最重要, 发现抗原检测几乎和聚合酶链反应检测一样准确, 如图所示.

如图所示, antigen tests make for ideal “infectiousness tests” and indicate most accurately whether someone is still within their approximately two-week infectious phase. PCR检测在整个感染生命周期中更为准确, 可以持续4 - 6周, 无论个体是否具有传染性.

培训我们的团队取得现场成果

至关重要的, 抗原检测可由任何受过培训的人员在现场进行, while PCR tests require shipment to a third-party lab with highly trained professionals required to run the tests and interpret the results. 目前, there are 11 members of the 保利预科 Health Team who have been trained to swab for a rapid test and 12 more who have been trained in assisting with the process and interpreting and recording the results. 

Dr. 米娜已经阐明了不同测试的最佳用途. For more information about his research and guidance, we recommend the following articles:

• 快速检测COVID-19——开放学校，拯救生命
• 研究表明，频繁、快速的检测可能会在几周内削弱COVID-19
• 冠状病毒:与Michael Mina的新闻发布会，11/18/20
• 冠状病毒:与Michael Mina的新闻发布会，11/20/20
• 如何修复COVID-19检测:在家每日快速检测

We believe that the combination of gate testing via PCR with individual swab collection, 如果时间允许的话.e., 在学校休息后)和每周或更频繁的抗原检测, provides the most comprehensive solution possible to our community given today’s technology and clinical realities.

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If you’d like to speak directly with someone from Poly about how our COVID-19 strategy allowed our students and faculty to return to and remain safely in school, 请与我们的 通信办公室.

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Read more about how Poly successfully continued the business of teaching and learning, 同时在COVID-19期间保持我们社区的安全: