Diagnostic COVID-19 Testing: Molecular and Antigen Tests

As of mid-November 2020, over 1 million people in the United States are being tested for COVID-19 every day.¹ However, all COVID-19 tests are not created equal. COVID-19 tests vary in how the sample is taken, how quickly you can get results, what they test for, and the accuracy of the results.² It’s important to know the differences in types of COVID-19 tests so you can make informed decisions about your own COVID-19 testing.

There are two general categories of COVID-19 testing: diagnostic and antibody testing. Diagnostic tests show if you have a current, active case of COVID-19, while antibody tests indicate if you’ve been infected by COVID-19 in the past.² In this blog, we will get into more detail on one of these categories: diagnostic COVID-19 testing.

\"\" — A doctor in a protective suit taking a nasal swab from a person to test for possible coronavirus infection

Diagnostic COVID-19 Tests

As mentioned above, diagnostic tests tell you if you have an active COVID-19 diagnosis. Two types of COVID-19 tests fall under the category of diagnostic testing: molecular tests and antigen tests.² Both of these tests typically use a nasal or throat swab. However, molecular and antigen tests differ in 1) which part of the COVID-19 virus particle they detect; 2) how quickly you will get results; 3) whether the sample is sent to a laboratory or handled completely at the patient care setting (i.e., “point-of-care”); and 4) the accuracy of the results. First, we will discuss molecular tests, which are the current gold standard for COVID-19 testing.³

Molecular COVID-19 Tests

Category: Diagnostic test
Includes: PCR tests, LAMP tests, and NAAT tests
Testing method: Nasal or nasopharyngeal swab
Detects: Viral genetic material
Turn-around time: <1 day – 1 week
Point-of-care: Typically, the sample must be sent to a laboratory for testing.
Accuracy: Very accurate (highly sensitive and highly specific)

Antigen COVID-19 Tests

Category: Diagnostic test
Testing method: Nasal or nasopharyngeal swab
Detects: Protein(s) in a virus particle
Turn-around time: <1 hour
Point-of-care: Testing is started and finished in the patient care setting (e.g., doctor’s office).
Accuracy: Less accurate than molecular tests, but still helpful. Positive test results are considered very accurate, but false negatives may occur in up to 20% of tests. For this reason, many experts suggest that if you receive a negative antigen test result, you confirm with a molecular test.

Summary

Need to know if you have COVID-19 right now? You need a diagnostic COVID-19 test! Antigen tests are generally quicker and cheaper, but less accurate than molecular tests. If your testing needs aren’t as time-sensitive (e.g., if you just need results in the next week), molecular tests are the way to go.