Updated September 2, 2020
How to know if you have, or have had exposure to the SARS-CoV-2 virus
More and more tests are available every day. Should you get tested? What does the results mean?
The value of the tests in predicting whether you have been exposed to the virus greatly depend on prevalence (number of cases) of the infection in your community, how the sample is collected, and what test is used.
The presence of antibodies is not the same as immunity. It simply means that you have been exposed to it, possibly, at some point in time. Length of any immunity, as known at this time (September 2020), is estimated to be about 4 months.
Want to get tested?
Molecular test
- Method
- What it detects
Viral RNA in nose or throat swabs
- How accurate
About 95%
- Use and Timeframe
• Current infection
• Day 3-7 of illness - PRO
• Well-validated
• Result within 15-30 mins (for rapid versions) - CON
• Cumbersome collection
• Longer time for results (if sent to lab) - Verdict
The Gold Standard
Antigen Test
- Method
- What it detects
Viral antigen (a part of the virus) in nasal swabs
- How accurate
About 80-90%
- Use and Timeframe
• Current infection
• Day 3-7 of illness - PRO
• Simpler collection
• Result within 15-30 mins - CON
• Miss 1 in 5 cases of infection
• High chance of false negatives - Verdict
A good enough alternative in some cases
Antibody test
- Method
Blood draw
- What it detects
Antibodies to the virus in the blood sample
- How accurate
About 72%
- Use and Timeframe
• Current or past exposure
• Day 10-14 of illness - PRO
• No swabs required
• Performed at major labs - CON
• High change of false positives
• Some has no antibodies → false negative - Verdict
Intepret with caution
Antibody test
- Method
Fingerprick
- What it detects
Antibodies to the virus in the blood sample
- How accurate
About 64%
- Use and Timeframe
• Community survey
• After day 14 of illness - PRO
• Least expensive
• Result within 15-30 mins - CON
• False positives: cross reactivity
• False negatives: no antibodies after infection
• Poor accuracy - Verdict
Skip these tests
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