What Will You Do If You Start Coughing? – The Atlantic

The sensitivity can be less than 100 percent and still be very useful, Ko says, in many cases. But as that number falls, so does the usefulness of any given result. In China, the sensitivity of tests has been reported to be as low as 30 to 60 percentmeaning roughly half of the people who actually had the virus had negative test results. Using repeated testing was found to increase the sensitivity to 71 percent. But that means a negative test still couldnt fully reassure someone like the teacher that he definitely doesnt have the virus. At that level of sensitivity, Ko says, if youre especially risk-averse, do you just say: If you have a cold, stay home?

An inaccurate testone prone to false positive or false negative results, can be worse than no test at all, Ian Lipkin, an epidemiology professor at Columbia University, told me in an email. The CDC has not shared the exact sensitivity of the testing process it has been using. When Fauci was asked about it on Monday, he once again hedged. If its positive, you absolutely can make a decision, he said. If its not, thats a judgment call. Usually a second test is recommended, and it depends on the patients symptoms, exposures, and how sick they appear to be.

The tests involve other variables, too. Samples must be taken using a long cotton swab that goes into the back of the patients nose (or mouth, though this seems to be a less sensitive method). In either case, sometimes you just dont get enough mucus on the swab. It can be hard to know if that was the cause of a negative test result when results come in from the lab a day later.

Read: The official coronavirus numbers are wrong, and everyone knows it

In attempt to increase sensitivity of the testing process, China not only swabbed people multiple times, but also added CT scans for an additional clue. The scans can sometimes help identify the unique patterns of lung damage caused by the virus, says Howard Forman, who practices radiology in the emergency department at YaleNew Haven Hospital. But scanning is a slow process to do at large scales, and its costly and involves exposure to radiation. You would need dedicated scanners as well, so as not to contaminate other patients, he told me. So it becomes very difficult to use CT for high-level screening.

Given the number of variables, widespread screening tests for the virus are not looming on the horizon as a way to obviate the urgent need for social distancing.

Some hope is being placed in biotech companies that are working to develop quick, mobile tests that could give results anywherebe it at a doctors office or in a modified parking lot. The goal would be to allow people to know if they have a cold or if they have the virus and need to self-quarantine, right there in the doctors office, says William Brody, a radiologist and former president of Johns Hopkins University. He is currently working on one such project with Hong Cai, a molecular biologist, at a small company called Mesa. The duo told me this is, at best, months away from being tested widely. Even then, its sensitivity will remain to be seen, and will likely be less than that of the current, slower tests. But Hong says her team is working as expeditiously as possible to solve the problem.

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What Will You Do If You Start Coughing? - The Atlantic