Information About Tests
Two types of viral diagnostic tests are used to determine if a person is currently infected with COVID-19.
If you receive a positive PCR/NAAT or antigen test result, you should isolate and inform your healthcare provider, as well as any close contacts. Correct interpretation of results from PCR/NAAT and antigen tests is important. If you have questions about your test results or symptoms, contact your healthcare provider.
|Accuracy||Highly sensitive at any point of infection; may remain positive for 90 days, even when person is no longer infectious||Moderate-high sensitivity at times of peak viral load; lower accuracy during low viral load (beginning or end of illness, asymptomatic illness)||Moderate-high sensitivity at times of peak viral load; lower accuracy during low viral load (beginning or end of illness, asymptomatic illness)|
|Result Time||1-3 days, generally; some can be less than 24 hours depending on lab capacity||10-15 minutes, generally||10-15 minutes, generally|
|Availability||Designated testing locations (pharmacies, doctor offices, health clinics)||Designated testing locations (pharmacies, doctor offices, health clinics)||For purchase at retail locations, pharmacies, online retailers, health clinics|
|Common Uses||Prior to travel (72 hours or less); asymptomatic testing; symptomatic testing; to verify antigen test results; before and after gathering||Surveillance at schools, workplaces and other congregate settings; symptomatic testing||At-home surveillance; symptomatic testing|
|When to use after potential or known exposure||Vaccinated: 5-7 days after exposure Unvaccinated: immediately after exposure notification; if negative, test again 5-7 days later||Vaccinated: 5-7 days after exposure Unvaccinated: immediately after exposure notification; if negative, test again 5-7 days later||Vaccinated: 5-7 days after exposure Unvaccinated: immediately after exposure notification; if negative, test again 5-7 days later|
|Price||Up to $150 plus cost of visit; many Greene County locations offer free testing or bill insurance||Up to $139 plus cost of visit; many Greene County locations offer free testing or bill insurance||Ranging from $10-$35, generally|
Reverse transcription polymerase chain reaction (often referred to as PCR tests) is a type of Nucleic acid amplification test (NAAT). This test detects genetic material of the SARS-Cov-2 virus in the individuals’ specimen. The Centers for Disease Control and Prevention (CDC) deems PCR/NAAT tests the gold standard (most accurate) COVID-19 test. These tests copy, or amplify, genetic material in the sample so it is easier to identify SARS-Cov-2 if it is present.
PCR/NAAT samples are collected using a nasal or throat swab, or with a saliva sample. Result times vary from one hour to several days and are dependent on where the test is administered and processed. PCR/NAAT tests should be used to confirm uncertain results from antigen tests.
Due to their high sensitivity, PCR/NAAT tests can remain positive for weeks to months after initial infection with COVID-19. In this case, an individual may not still be contagious.
Analyte Detected: Viral Ribonucleic Acid (RNA)
Specimen Types: Nasal, Nasopharyngeal, Oropharyngeal, Sputum, Saliva
Sensitivity: Varies by test, but generally high for laboratory-based tests and moderate-to-high for point of care (POC) tests
Text Complexity: Varies by test
Turnaround time: Most 1-3 days; some could be rapid 15 minutes
Cost per test (not normally for the consumer): $75-$100
- Most sensitive test method available
- Short turnaround time for NAAT POC tests, but few available
- Usually does not need to be repeated to confirm results
- Longer turnaround time for lab-based tests (1–3 days)
- Higher cost per test
- A positive NAAT diagnostic test should not be repeated within 90 days, since people may continue to have detectable RNA after risk of transmission has passed
An antigen test detects viral antigens, which are parts of the virus that triggers the body’s immune response. The test performs best if the person is tested when their viral load is highest (e.g. is symptomatic, or early in the timing of their infection). Antigen samples can be collected via nasal swabs.
If COVID-19 antigens are present in the sample, they will bind to COVID-19 antibodies on a testing strip and display a positive result.
Antigen tests are ideal for self-testing, and many are available at pharmacies and other retailers. Results display within minutes, which is helpful for attempts to reduce transmission in congregate settings, group gatherings, travel, etc.
However, antigen test results have the potential to be less accurate and sensitive than PCR tests. COVID-19 antigens may not be at high enough levels to be detected by an antigen test prior to the onset of symptoms or near the end of COVID-19 infection. If you believe you could have COVID-19 and receive a negative antigen test result, it is recommended that you repeat antigen testing at least 24 hours later or confirm the result with a PCR test, especially if you develop symptoms.
Analyte Detected: Viral Antigens
Specimen Types: Nasal, Nasopharyngeal
Sensitivity: Varies depending on the course of infections, but generally moderate-to-high at times of peak viral load
Text Complexity: Relatively Easy to Use
Turnaround time: 15-30 minutes
Cost per test (not normally for the consumer): $5-$50
- Short turnaround time (approximately 15 minutes)
- When performed at or near POC, allows for rapid identification of infected people, thus preventing further virus transmission in the community, workplace, etc.
- Comparable performance to NAATs in symptomatic persons and/or if culturable virus present, when the person is presumed to be infectious
- May need confirmatory testing
- Less sensitive (more false negative results) compared to NAATs, especially among asymptomatic people