How test works The Stanford test uses a technique called reverse-transcriptase polymerase chain reaction, or RT-PCR, to rapidly identify the presence of viral RNA in swabs from the noses of potentially infected people. RT-PCR uses short stretches of DNA called primers that bind tightly and specifically only to matching sequences in SARS-CoV-2 RNA. An enzyme called reverse transcriptase then converts the viral RNA into complementary DNA, and as the reaction continues, an enzyme called polymerase is used to generate billions of DNA copies that can be detected by fluorescently tagged molecules called probes. Pinsky and his colleagues used primers and probes developed at a laboratory in Germany that has studied the SARS and MERS coronaviruses for many years. They then optimized the use of these diagnostic tools to meet the United States’ testing guidelines. The Stanford test screens first for the presence of viral RNA encoding a protein called an envelope protein, which is found in the membrane that surrounds the virus and plays an important role in the viral life cycle, including budding from an infected host cells. It then confirms the positive result by testing for a gene encoding a second protein called RNA-dependent RNA polymerase. The test used by the CDC screens for yet a third gene encoding a protein that forms the viral nucleocapsid that forms a kind of shell around the viral genetic material. The availability of a variety of tests targeting different viral-specific RNA sequences will provide an important way to cross-confirm laboratory results.”
California declared a state of emergency after the first death was confirmed there Wednesday. A cruise ship that the victim had traveled on was being held offshore in San Francisco while passengers are tested for the virus. Officials said 35 people on the ship had symptoms of the coronavirus.
California declared a state of emergency after the first death was confirmed there Wednesday. A cruise ship that the victim had traveled on was being held offshore in San Francisco while passengers are tested for the virus. Officials said 35 people on the ship had symptoms of the coronavirus.
特别是今天在各处看到的假消息所谓“已经开始采用病毒复制率检测手段，比核酸检测灵敏快速多了”。
稍微搜索了一下，请有生化背景的同学仔细读读下面这篇三天前发表在 the scientist 杂志上的综述评论文章：
https://www.the-scientist.com/news-opinion/how-sars-cov-2-tests-work-and-whats-next-in-covid-19-diagnostics-67210
主要内容稍微总结一下：
1. WHO 建议和世界上绝大多数国家正在采用的检测方法仍然是德国人开发的鼻咽拭子RT-PCR核酸检测法，主要检测病毒的部分基因片段E gene (在病毒蛋白壳上表达)，属于筛查screening性质，假阳性率目前0%， 但是假阴性率比较高。筛查阳性病人可以依靠全基因测序完全确诊。
2. 目前只有美国CDC采用自己开发的基于检测 N gene 基因片段的RT-PCR， 文章里提到哈佛的研究人员也很困惑CDC如此做法“到底是为了什莫？”
3. 以上两种目前主流RT-PCR方法可以满足疫情早期发展需要，但是48小时的检测时间和假阴性问题，对爆发式增长的检测需求无法适应。
4. 目前正在开发但是短期内仍无法投入临床检测实用的方法 1： CRISPR based 检测法， 对，就是大名鼎鼎的CRISPR/cas9基因编辑里的CRISPR, 已经有研究机构开发出可以标的检测任何病毒的原型产品，包括MIT的paper strip一小时检测原型，据说更sensitive，但文章没有进一步说明是否解决假阴性问题。而且离临床实用都还很远。这个CRISPR的原文很拗口，被某些中文媒体微信小道消息翻译成“病毒复制率”检测法，并且谣传已经开始使用比核酸检测甩几条街云云，只能一声叹息，有未知就有谣言的生存空间。
5. 方法2 ： 抗体 antibody 检测法，很多研究机构包括新加坡和台湾的，都在打治愈和轻症COVID-19病人的主意，因为人体内的获得性(adaptive)免疫系统会人体跟病毒斗争大约一周以后开始产生抗体，自愈和轻症病人最有希望能分离出相关的病毒抗体。研究人员希望将抗体检测法应用于大范围人群检测，以期获得无症状自愈病例的数据，以更好了解COVID-19病毒。换句话说，抗体检测法有点马后炮的意思，并且也是短期内无法应用临床。
就这样。希望大家秉持了解的事实越多，越不容易恐慌的信念，安全度过疫情，继续好好生活。
Stanford的试剂盒也是rt-PCR based，但是分两步测，先测e protein，阳性的话，再测另外一个这个病毒专属的基因。
How test works The Stanford test uses a technique called reverse-transcriptase polymerase chain reaction, or RT-PCR, to rapidly identify the presence of viral RNA in swabs from the noses of potentially infected people. RT-PCR uses short stretches of DNA called primers that bind tightly and specifically only to matching sequences in SARS-CoV-2 RNA. An enzyme called reverse transcriptase then converts the viral RNA into complementary DNA, and as the reaction continues, an enzyme called polymerase is used to generate billions of DNA copies that can be detected by fluorescently tagged molecules called probes. Pinsky and his colleagues used primers and probes developed at a laboratory in Germany that has studied the SARS and MERS coronaviruses for many years. They then optimized the use of these diagnostic tools to meet the United States’ testing guidelines. The Stanford test screens first for the presence of viral RNA encoding a protein called an envelope protein, which is found in the membrane that surrounds the virus and plays an important role in the viral life cycle, including budding from an infected host cells. It then confirms the positive result by testing for a gene encoding a second protein called RNA-dependent RNA polymerase. The test used by the CDC screens for yet a third gene encoding a protein that forms the viral nucleocapsid that forms a kind of shell around the viral genetic material. The availability of a variety of tests targeting different viral-specific RNA sequences will provide an important way to cross-confirm laboratory results.”
California declared a state of emergency after the first death was confirmed there Wednesday. A cruise ship that the victim had traveled on was being held offshore in San Francisco while passengers are tested for the virus. Officials said 35 people on the ship had symptoms of the coronavirus.
好像不是確診，是疑似。
https://www.cbsnews.com/live-updates/coronavirus-outbreak-death-toll-us-infections-latest-news-updates-2020-03-05/
美国的FDA不是摆设啊，IVD必须过510K审批，没有特许不是一直只能依赖CDC做试剂盒么。 哎！
FDA流程没走完，就算能一张试纸一秒出结果也是枉然。
今天已经确诊了21个，这比例...
对，所以现在国内所谓“复阳”大概率是出院的国家标准太宽松。今天已经开始要加测血清学抗体检测了。也只有国内能这么火线上马各种检测。
微信上那个什么小顺的谣言聊天记录满天飞，实在是看不下去了。
要先分离出抗体才好做检测试剂不是么？
PCR是开发用来扩增微量DNA，最早在法医刑侦，考古等方面应用，后来在生化领域大放异彩。
现在应用在定向扩增病毒RNA的特定基因片段，比如E 或者N gene，以达到足够的基因片段滴度以供检测。
👌
SARS-COV-2的IgM和IgG难道不是特异的？
采的样品鼻咽拭子就是棉签深入鼻腔后部或喉咙刮擦取到上皮细胞，一个细胞理论上可以含有多达十万个病毒颗粒。在灭活前，这些样品是非常危险的。所以必须在负压实验室操作。
采样时，医护必须最严密的防护，因为直接近距离接触高浓度传染源，病人还会不受控喷嚏咳嗽，稍微防护上有漏洞就有可能被感染。
韩国drive through 只是取样，取样的人员也是防护到极致的。
既然是特异的，最初的 anti-human IgM/IgG secondary antibody 怎么生产的？不需要病人体内采集分离纯化的原始Sars-COV-2特异IgM/IgG抗体来生产抗-抗体？
国内现在直接上IgM/IgG抗体检测，还不是因为一有大量病例可以纯化抗体生产初始的anti-human secondary antibody，二来CFDA是摆设。
心平气和，好好讨论，如果有专业背景知识就多说两句补充完善，大家科普收益，有啥不好的？