COVID Testing Lingo

What do all these scientific terms mean? What’s an EUA or a CLIA lab?

Doctor in face mask preparing to take nasal swab of patient
Types of Tests

The FDA’s description of the three basic types of test for Covid-19: PCR or molecular tests, antigen tests, and antibody tests. Good for lay readers.

Diagnostic vs. Screening vs. Surveillance

The CDC’s guidance for rapid antigen tests reviews the differences between these three types of testing. Read this – it’s a distinction you’ll need to be familiar with.

Even More Types
of Tests

More in-depth descriptions of all the tests that are – and could be – used to diagnose Covid-19. Written for lay readers; includes definitions of basic scientific terms.

What is an EUA?

There are no “FDA-approved” Covid tests. The highest level of approval any of them have is an EUA – Emergency Use Authorization – from the FDA. Here’s what that means.

Image adapted from
the Louisiana Dept. of Public Health
What’s the difference between a nasal and a nasopharyngeal swab?

A nasal swab – also called an anterior nasal swab – isn’t nearly as deep as a nasopharyngeal swab (see image above). A mid-turbinate swab is between the two.

What is a CLIA lab,
and why does it matter?

Basically, it’s a lab that has been certified by the US government. There are different levels of CLIA certification, based on the complexity of the tests the lab is certified to run.

What are sensitivity
and specificity,
and why should I care?

A brief, easy-to-understand explanation from the NY State Department of Health. Also explains predictive value. Start reading after the section on screening tests.

Image by Arek Socha from Pixabay
I still don’t quite get the difference between sensitivity and positive percent agreement.

A comic-strip explanation of the difference between sensitivity/specificity and positive/negative percent agreement.

A positive message. Photo by Ian Taylor on Unsplash.
Positivity vs. Prevalence (Concentric by Ginkgo)

“Prevalence means the proportion of people who are infected at a given time.” So if your community’s COVID-19 prevalence is 5%, that means about 5% of the people in your community have COVID-19. This is the number that really tells you what the coronavirus risk is in your area.

Percent positivity means something different: of the people who were tested, what percentage tested positive? If you’re only testing people with symptoms, your percent positivity is probably higher than your prevalence.

Image from WBUR
How to Read the Official
Covid-19 Numbers

Cases per 100K rising +
test % positive rising = BAD.
Cases per 100K falling +
test % positive falling = GOOD.
If there’s a disconnect between those two metrics, you’ll have to look deeper.

Image downloaded from site below on 11.16.20
Covid-19 Risk Assessment Planning Tool

This map shows the risk level of attending an event, given the event size and location.

Johns Hopkins Overview of Covid-19

All the details about the disease. Written for physicians or bio nerds.

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