So you want students to come back to campus as long as they can show a negative COVID test, huh? #LRT Let's break this down.

A negative test result does not = COVID-free. Why? B/c no test is perfect. One way to measure the accuracy of tests is sensitivity. 1/7

A sensitivity of 100% means that if you have 100 people with the disease the test will detect it in all of them.

How good are COVID tests? Some are 70% sensitive, some 90% ( https://www.nejm.org/doi/full/10.1056/NEJMp2015897). Different labs use different tests, which complicates interpretation. 2/7

Then there's pre-test probability, i.e. the chances you have COVID to begin w/. A negative test for someone who might have been exposed (among unmasked crowds on vacation, or partying on campus over the summer) is more questionable than for someone who spent summer at home. 3/7

How are colleges going to account for different pre-test probabilities for different students? I'm guessing they...won't.

Also, the @NEJM article points out that we actually don't have sensitivity data for many of the commercial COVID tests available in the USA. 4/7

Here's another issue: let's say a student has been exposed to COVID but is still in the incubation period of infection - meaning the virus is in their body, replicating, but they don't have symptoms and aren't infectious yet. This person may test negative. 5/7

Or maybe a student truly doesn't have COVID and tests negative, but then catches it between the date of their test and their arrival on campus.

As you can see, there are many serious problems w/ the plan to allow students back on campus if they've had a negative COVID test. 6/7

Such a plan is not in the best interest of public health. At worst, it could be catastrophic for the communities in which these colleges and universities are located. It will deepen the disparities we've already observed in this pandemic. #HigherEd admins, DO THE RIGHT THING. 7/7